EXPLORATIONS INTO PREHISTORIC POTTERY REPLICATION: A PRELIMINARY REPORT

Volume 2 College of Southern Nevada Four Fields: Journal o f Anthropology 2013

EXPLORATIONS INTO PREHISTORIC POTTERY REPLICATION:

A PRELIMINARY REPORT

Sally Llull Billings and James LaFleur

ABSTRACT

Artifact replication is a branch of experimental archaeology that attempts to reproduce artifacts

found in the archaeological record using, whenever possible, traditional techniques and tools. In

this study, the methods for replicating coil and scrape pottery from the American Southwest are

explored including collecting and processing local clays, hand building, decorating, and painting

several types of vessels, making organic paint, and firing. The use of different types of temper

and the effect of environmental conditions, such as temperature and humidity, on the process of

hand building a pot will be highlighted.

INTRODUCTION

Clay is one of the most common types of sediment found all over the world; it is plastic

and malleable and is used in a wide variety of applications: as a building material, to make

figurines and jewelry, for plumbing, as early writing tablets, in cosmetics, and lastly, but not

least, to make pottery. Humans have made pottery since the Neolithic in Eurasia (Blandino

2003:11-12) the Archaic in Mexico and Central America (Evans 2013:96), and, in East Asia, as

early as the Paleolithic (Zhushchikhovskaia: 2012). Pottery is one of the main chronological and

cultural diagnostic markers recognized by archaeologists the world over; vessel form, design


elements, and function help archaeologists place sites within a cultural and temporal framework,

and also to understand a multitude of issues such as, but not limited to, culture change,

subsistence strategies, and settlement patterns. The archaeological literature abounds with

discussions on the various forms of ceramic wares found in many ancient societies, of the types

of temper used in the paste, of the effects of firing – low oxygen versus high oxygen, reduction

techniques, etc. - on different types of clays. Ceramics can be either hand-built or thrown on a

wheel. The hand built techniques most often described in the literature include coil and scrape,

paddle and anvil, pinch pots, and molds. Some authors may briefly describe the steps involved in

hand building, however, none come close to conveying the time-consuming, complicated process

that each technique entails, nor the incredible skill that is required to produce a viable finished

product.

Producing usable pottery is a skill that can take a long time to perfect, starting with the

acquisition of the proper type of clay and how to process that clay so one can create the right

paste to produce the various wares, to the right types of fuel and temperatures to fire the green

ware. Ceramic replication is an important tool for examining and understanding these processes,

however, there have been relatively few replication studies published in professional literature.

Experimental Archaeology and Replication Studies

Experimental archaeology, which dates to the mid-to-late 19th

century, is a branch of

archaeology that seeks to interpret the material culture of the past through scientific

experimentation or replication of said material culture (Callahan 1999:4; Shimada 2005:604).

Experimental studies have included, but are not limited to garbology projects (Rathje and

Murphy 1992), the building of monumental structures found in the archaeological record such as

Stonehenge (Parker Pearson 2011:252), and the construction and sailing of an ancient Viking-


type ship (Shimada 2005:603). Experimentation has been an important tool in the advancement

of method and theory, particularly for the early functionalists of the 20th

century who used this

approach to develop middle range theories that allowed “…the accurate conversion from

observations on statics [material remains] to statements about dynamics [the past culture]”

(Shimada 2005:604). Experimentation in archaeology can also “…provide certain kinds of data

unobtainable by more conventional studies of artifacts” (Saraydar and Shimada 1973:345). In the

mid 1960’s Don Crabtree and Francoise Bordes demonstrated the utility of an experimental

approach to lithic studies by reproducing stone tools and thus encouraged many future

archaeologists to learn flintknapping (Callahan 1999:4). Flintknapping has been a popular

technique utilized in use wear studies.

Replication studies, as a subdivision of experimental archaeology, entails reproducing the

material culture found in the archaeological record or described in ethnographic accounts using

the methods and materials that would have been available to the peoples whose technologies are

being reproduced (Callahan 1999). Reproducing the material culture of prehistoric peoples can

be problematic due to the absence of documented sources that could shed light on the process of

making both utilitarian and luxury items, and identifying the precise materials required to

produce these items. Replication studies run the gamut from flintknapping and pottery making,

to reproducing whole ancient structures and from the utilitarian to the non-utilitarian. It can

provide insight into form and function, the procurement and preparation of raw materials, and the

challenges and obstacles ancient people faced when attempting to produce the goods they needed

in their everyday lives.

Experimental archaeology has had its share of challenges and criticisms; as early as the

1960’s critics have stated that the evaluation of procedures and results of archaeological


experimentation are at best ambiguous due to a fundamental lack of a clear theoretical focus

(Shimada 2005:608). Outram (2008) outlines five deficiencies common to archaeological

experiments: 1) lack of clear aims, 2) insufficient detail on materials and methods, 3)

compromises over authentic materials, 4) inappropriate parameters, and 5) lack of academic

context. Replication of archaeological materials and sites tend to be very susceptible to these

deficiencies particularly when replicators, who are usually amateurs, often lack the academic

background and training necessary for a rigorous scientific approach in their work.

Around the 1980’s the experimental approach waned in the United States but increased in

Europe, where today the practice is an important component of many archaeological studies

(Callahan 1999: 5). Over the past fifteen years or so, experimental archaeology is once again

experiencing resurgence in the U.S., with many colleges and universities developing

experimental programs that are based in sound scientific method (Marsh and Ferguson 2010:3-

4). Carefully designed scientific experiments take into consideration the types of tools and the

raw materials they were made from that were available to prehistoric peoples, and a careful

analysis of the procedures used to produce goods. The results are then scientifically monitored

through testing (Callahan 1994:5).

One notable area in experimental studies focuses on the reproduction of prehistoric

ceramics. Pottery making in the American Southwest has had a long, continuous tradition

beginning in the 8th

century A.D. to the present day. Modern Puebloan potters have learned their

craft from parents or grandparents who also learned it from kin who passed down this knowledge

relatively unchanged through the generations. While some innovation in decorating techniques

was developed in the late 1800s in response to a growing demand for native goods by American

and European collectors, the basic techniques for collecting and processing clay and hand-


building pots has remained unchanged for well over a thousand years. This has made the process

of replicating archaeologically-based examples more feasible than replicating many other now-

extinct technologies. Through hands-on instruction native potters have shared the knowledge of

pottery making with non-indigenous enthusiasts and scholars (Hayes and Blom 1996; Swink

2004).

Using replicated ceramics in experimentation may be more desirable than using

archaeological sherds. First and foremost, it serves to preserve the archaeological record in that

ancient pot sherds will not be destroyed; replicates are more dispensable. Secondly, using whole

replicated pots rather than archaeological pots sherds allows research into how different technical

choices can affect the performance of ceramic pots (Harry 2010: 43-44)

The emphasis of this study is the replication of Southwestern ceramics in order to better

understand the process of collecting and processing the proper materials, such as clay and

temper, the use of different tools made from locally available materials, and the technique of

hand-building vessels, as well as creating decorated wares and firing. The purpose is not to

generate theoretical statements per se, but to serve as a launching point for further research and

hypothesis-building. Without a fundamental understanding of the steps and challenges involved

in making pottery, the ability to generate new questions to direct future research seems limited.

WHAT IS CLAY?

Clay is difficult to define because it has been used to describe a variety of materials that

differs from one another in both composition and origin. Definitions for clay and clay minerals

can vary depending on who one asks; for geologists “clay mineral” refers to a class of hydrated


phyllosilicates, or in other words, a mineral high in silicates (Bergaya and Lagaly 2006:5). It is

the silica in the mineral which gives clay a plastic quality when mixed with water and hardens

when dried or fired. A ceramist may define clay by their firing properties or by their uses

(Shepard 1980:7). In essence, clay is the end result of a weathering process of specific minerals

in rock which produces a conglomerate of various components. Reijnders identifies eleven main

components found in many types of clay that includes clay minerals, quartz, mica, feldspar,

calcium and magnesium-containing associate minerals, iron-containing associate minerals,

titanium oxide-containing associate minerals, and organic materials (2005:237).

Clay minerals are composed of a group of small crystalline particles of one or more

members of a group that are commonly known as clay minerals. Clay minerals are hydrous

aluminum silicate, which in some minerals, can be replaced by iron and magnesium (Murray

2007:7). There are some groups of clay minerals that are relevant to pottery production which

include the kaolinites, the illites, and the smectites or montmorillonites (Bergaya and Lagaly

2006:3-5; Murray 2007:7-15; Reijnders 2005:273-274; Shepard 1980:6-10).

Other mineral components can impact the properties of clay, for instance, the presence of

fine-grained quartz in a kaolin clay may impart an abrasiveness to the clay, while organic matter

may affect color (Murray 2007:2). The presence of soluble salts can cause clay to flocculate,

that is, form lumps, which can create problems in processing the clay for use. Montmorillonite

clay that is high in calcium is more viscous than those that are high in sodium, which makes it

suitable for making pottery.

Plasticity and Texture

Clay plasticity refers to the ability of the material to be molded into a shape without it

breaking when a certain amount of stress or pressure is applied and for the shape to be retained


after the pressure is removed (Bergaya and Lagaly 2006:5). Clay particles absorb and retain

water; the particles in clay are surrounded by water which acts as a lubricant that allows mineral

plates to slide across one another (Shepard 1980:15). When water is added to clay, the clay

minerals form a suspension that is composed of particles in a size range between molecules and

grains that is called the colloidal state. Clay colloids attract water molecules to their surface and

form “water hulls” (Shepard 1980:14).

Clay Types Based on Origin and Sources

Raw clay deposits suitable for making pottery can be found in a number of geological

contexts. Alluvial clays are those that have been transported and deposited by water as alluvial

fans, and often contain a high iron content (Swink 2004:19). This type of clay is often found

along river banks or other water courses, as well as within ancient alluvial deposits. This type of

clay often fires at lower temperatures which is typical of prehistoric wares.

Carbonaceous clays are found in shale deposits from sedimentary geological formations

(Swink 2004:19) that has been laid down as ancient seabeds or other bodies of water, and is very

fine-grained. This produces a highly plastic claybody, making it ideal for pottery.

Montmorillonite clays are decomposed volcanic ash and are characterized as very fine-

grained clays that are also found in sedimentary geological formations (Swink 2004:19). This

clay is often ideal for creating slips and also as an additive to other clays to increase plasticity.

Clint Swink, a ceramic replicator from southwestern Colorado, has made replicas of

Mesa Verde plain and painted wares using all three types of the afore-mentioned clays. His

preference is for the carbonaceous clay that is abundantly available on the Colorado Plateau and

which he claims the prehistoric Mesa Verde potters used extensively due to its high degree of


plasticity (2004:19). These same potters also used montmorillonites as slips for their painted

wares.

Clay often stands out from the surrounding soils and can be visually identified cursorily

by color and texture. Soils that change color dramatically from one stratum to the next are

frequently clay veins. Another telltale sign of the presence of a clay deposit is the lack of

vegetation growing within the area of the deposit that prevents water penetration from reaching

the roots of plants.

The texture of clay when wet is usually smooth and sometimes unctuous. Carbonaceous

clays, due to the very fine particle size, tend toward an unctuous feel. This can result in a smooth

pottery vessel, which may be why this type of clay may have been favored by Mesa Verde

potters.

MAKING POTTERY

Clay Processing

Preparation of the claybody is a crucial first step before making the paste. If the material

is not properly processed, it can cause the paste to crack during hand-building, drying, and firing.

Only those methods that indigenous potters may have used will be discussed.

Grinding or slaking the raw clay removes unnecessary particulates such as small rocks

and vegetative matter and reduces the clay and other mineral particles to a fine, uniform size that

aids the preparation of the paste (Blankenship and Blankenship 2008:116; Jamison 2007: 39;

Peterson and Peterson 2009: 39-40; Shepard 1980:51; Swink 2004: 21-22) (Figure 1). These fine

particles will ensure that when the clay is mixed with water, the water will be absorbed and

distributed evenly throughout the paste. In the American Southwest the native peoples used


manos and metates made from a number of different materials, including sandstone, basalt, and

quartzite to grind clay (Swink 2004).

Figure 1. Grinding clay

Temper and Plasticity

Temper is a nonplastic material that is added to the clay to mitigate shrinkage and prevent

cracking as it dries (Blandino2003:25; Shepard 1980:53; Swink 2004:22-23). Once clay has been

ground, temper is added to the mix (Figure 2). Because clay tends to absorb large quantities of

water, making it plastic and pliable, it shrinks as it dries. Nonplastic additives aid in uniform

drying by creating “escape paths for moisture” (Swink 2004:22).


Figure 2. Adding temper.

Determining the correct amount of temper to add can be complicated. Too much temper

will render the paste unworkable due to a loss in plasticity while too little temper may yield a

vessel that will crack upon drying or firing because of excessive shrinkage. On the other hand,

the more temper a clay body has, the less likely it will be to crack during firing but will

ultimately produce a weaker vessel (Harry 2010:52-53). There is no “magic formula” for adding

temper as each clay possesses different mineral and chemical properties (Shepard 1980), and is

already self-tempered to varying degrees. Finding the right consistency is a balancing act

between preserving the workability of the clay with producing a crack-resistant vessel. Clays that

are less plastic, whether occurring naturally or due to the addition of excessive temper are called

“short”, while those that are highly plastic are referred to as “fat” (Peterson and Peterson 2009;

Shepard 1980; Swink 2004: 24).

In the American Southwest several nonplastic materials were used as temper including

sand, crushed basalt, and crushed pottery. Crushed sherd temper was used by Chaco and Mesa

Verde potters (A.D. 700-1300) to make fine white wares that are found throughout the Ancestral


Puebloan heartland (Hayes and Blom 1996: 44; Swink 2004). These wares were not used for

cooking as sherd-tempered ceramics did not stand up very well to thermal shock resulting from

repeated heating and cooling (Blinman 2013:64). Shivwits Plain wares dating to Pueblo II times

(A.D. 900-1100) are described as having crushed sherd temper and have been found in the

Moapa Valley (Harry 2005:310; Lyneis 1992:45-49).

Crushed igneous (basalt) rock temper was used extensively in the Four Corners area

during Basketmaker III (A.D. 400-725) (Toll and Wilson 2000:28) and Pueblo III times (A.D.

1150-1300) (Swink 2004:23). This type of temper may have been preferred for cooking vessels

because rock temper confers greater thermal stress resistance, making it ideal to withstanding

repeated heating and cooling (Pierce 2005:134).

Sand temper was widely used in the Great Basin and Mohave Desert, and is found

throughout sites in the Moapa Valley around the Muddy and Virgin Rivers such as Bovine Bluff

(Myhrer and Lyneis 1985:19-25), and Main Ridge (Lyneis 1992:41), although limestone

tempered pottery such as Logandale Gray Ware is predominant at these sites. The abundance of

sand may be a primary motive for its use in pottery. Sand was used extensively in gray wares

from the La Plata and upper San Juan Valley in northwestern New Mexico to produce cooking

vessels (Toll and Wilson 2000:19; Wilson and Blinman 2000:71). The addition of sand temper

consisting of rounded grains tend to produce weaker vessels than using sand (or crushed

sandstone or igneous rock) with angular grains (Blinman 2013). Quartz, feldspar, and mica are

frequently found in sand and are visible when examining cross sections of sand-tempered sherds

under a hand lens.

Fine-grained tempers tend to produce stronger wares than coarse-grained tempers

(Blinman 2013), although coarse-grained tempers may have been preferred for cooking vessels


because of greater resistance to thermal shock (Skibo et al 1989:123). Therefore, with the

exception of fine sand, most other tempering agents benefit from grinding prior to adding to the

clay.

Wedging

Wedging is the process of kneading the tempered clay when water is added to produce a

paste (Blandino 2003:23-25; Jamison and Jamison 2007:39; Peterson and Peterson 2009 39-40;

Shepard 1980: 51-52; Swink 2004: 27-28) (Figure: 3). This is a vital step in the preparation of

the paste; to ignore or neglect this step in any way will result in a substandard paste that is

unusable for making ceramics. The function of wedging is several-fold: it a) increases plasticity,

b) removes air bubbles that create air pockets which weakens the vessel and promotes cracking,

c) distributes water and temper evenly through the mix, d) promotes homogeneity and

consistency of the mixture, and e) removes excess moisture from the paste.

Figure 3. Wedging clay.

There is no single method for mixing a clay paste. Among the Ibibio from the Kavango

region of northern southwest Africa and at Multan, Pakistan, clay and temper are hand mixed,

then water is added and the whole is trampled on (Blandino 2003:23; Rice 1987:123). Swink


(2004) describes that wedging in the Southwest is done by hand by starting with a rough ball of

clay, holding it in the left hand, and with the right hand lifting a corner of the clay, folding it

inward, and pressing down into the clay while the left hand rotates the clay counterclockwise.

Swink reports doing this at least one-hundred and twenty times to ensure the complete

incorporation and distribution of water and temper into the clay mix, and to remove air bubbles.

Another method is called the “cut and slap” method (Peterson and Peterson 2009:40) whereby a

slab of clay two to three inches thick is thrown down onto a table or other hard surface, then

adding another slab of the same thickness by slapping that onto the first slab, making certain no

air remains between the slabs. Several slabs may be added consecutively to the mass. This

method can be problematic due to the risk of trapping air between the slabs. Occasionally the

combination of two different types of clays may improve plasticity and workability (Tite 1999).

Once the paste has been prepared and wedged, it may be used immediately but ideally

should be stored for a period of time in a sealed container. Swink (2004:24) recommends storing

the clay in several plastic bags and then in a tightly sealed container to “age”. As the clay body

ages, it breaks down into finer particles and increases plasticity. Another benefit of aging clay is

that it allows thorough absorption and distribution of water into the mix, and favors bacterial

action that speeds up the process of breaking down clay particles (Blankenship and Blankenship

2008: 116; Shepard 1980:52). Swink (2004:24) collects pond scum and adds it to the clay body

mix because of the bacterial organisms present in the water. There is little to no reference of

storing clay in the archaeological record although it is possible that pre-mixed clay body could

easily have been stored in ceramic jars, sealed baskets, or in small subsurface pits for later use.

Ceramic jars would have been ideal as they tend to absorb and retain moisture, which is essential

for preserving the mixed clay body. Shepard (1956) mentions the possibility that clay was stored


before use by the Aymara of the Andes and the Navajo in the American Southwest, but does not

provide any details of the practice. Rice (1987:119-120) also mentions some ethnographic

examples of aging clay; the Papago potters of Arizona age their clay over the winter while

potters in Chamula, Mexico, age their clay for up to a year. Adding small amounts of acidic

substances may hasten clay aging.

The type of water used is another important variable for the successful mixing of a clay

paste. Groundwater in many areas contains soluble salts, which may present problems when

drying and firing a vessel. Soluble salts create what is called “florescence” or “bloom” (Swink

2004:25) which is the migration of salts to the vessel wall during drying. This creates difficulties

when trying to burnish and slip the vessel because of the powdery finish that collects on the

surface. Water may also contain a high iron content which can cause problems with slipping a

vessel. White slips may yield a pink tone when firing in highly oxidized environments or turn a

dark gray in reduction atmospheres. One of the ways to reduce these problems is by using

rainwater however in Southern Nevada where rainfall is sporadic and unpredictable, using

distilled water is acceptable for replication studies because there is an absence of minerals in the

water.

Hand-Building Pottery

The tools used in pottery making are diverse and can be made from a variety of materials.

Tool types include scrapers for smoothing vessel walls, smooth pebbles for burnishing and

polishing, threads made from agave fibers for cutting, paintbrushes made out of agave fibers for

slipping and painting decorations, a mold called a puki made from an older pottery bowl, a soft

piece of leather or cloth for polishing, a piece of sandstone for sanding and smoothing a dry

vessel, a flake of chert or obsidian, or sharpened bones for use as a cutting tool, organic or


mineral paints, and a smooth, flat surface to work on. Scrapers can be made from different

materials such as gourd, broken pot sherds, or even stone flakes.

Coiling is the method used throughout the American Southwest for building a vessel’s

walls. They can be stacked one on top of the other, and pinched and smoothed, overlapped, or

used in a continuous spiral from the vessel base to the rim (Blankenship and Blankenship

2008:117-118; Jamison and Jamison 2007: 43-44; Peterson and Peterson 2009:43-45; Shepard

1980:57-59; Swink 2004: 28). Coiling ensures a certain degree of uniformity in wall thickness

and may offer some compensation when working with less plastic clay. An advantage of

overlapping is that a stronger bond can be applied between coils rather than merely pressing

down on superimposed coils.

Coils are made by rolling a ball of clay back and forth on a flat surface using both hands

and applying gentle pressure. The roll is lengthened and smoothed by rolling from the middle out

to the sides (Figure 4). During rolling the coil, the ends can form hollow depressions that can

trap air into the mix and should be pinched closed as soon as they form. Swink (2004) refers to

these as “snake mouths”. Swink prefers to use fewer coils because the more numerous the coils,

the weaker the vessel tends to be. In archaeological specimens it is sometimes possible to find

the juncture between coils by touch which feels like a slight bump or ridge on the vessels walls.


Figure 4. Making a coil.

A base is made by either molding clay inside of a puki, or by creating a coiled based

(Blandino 2003: 28; Blankenship and Blankenship 2008: 117; Jamison and Jamison 2007: 43;

Swink 2004: 96). First, a ball of clay is shaped into a disk and is thinned and stretched by

slamming it onto a hard surface (Swink 2004: 96-99) (Figure 5). This helps to eliminate any

trapped air in the clay. To continue stretching the disk, it is thrown toward the individual at an

angle, in much the same way as pizza dough, which stretches the clay in the direction of the

throw. The clay disk is picked up, rotated 90º, and repeated until the desired size and shape is

achieved.


Figure 5. Making the clay disc.

The thickness of the base should range between five and seven millimeters, depending on

the size of the vessel. Once this happens, the clay is carefully centered over the puki and gently

pushed to the bottom with the back of the hand (Figure 6). Uneven thinning of the base can cause

the vessel to crack when firing. The walls are smoothed out using a scraper or hands, the rim is

trimmed so that it is even for attaching the coil and the entire based is turned out upside down

onto a hard surface to set. Inverting the bowl allows the vessel to retain its arched shape and

keeps it from collapsing.


Figure 6. Placing the disc in the puki.

Minor cracks, which should not be confused with natural stretch marks, can be removed

at this point simply by smoothing over with a finger or by patching it with a thin mixture of clay

and water. The base must be firm enough to support the weight of additional clay so enough time

should be allowed for drying before attaching coils.

The vessel’s walls are built by adding coils to the base. When the base has set sufficiently

it is flipped over and the lip is trimmed and lightly scored using a flake, and moistened with clay

water to ensure that the coil will adhere to the rim (Figure 7). Clay water or “slurry” is preferable

to plain water as the clay particles in the water create a bond with the clay in coils and vessel

walls, enhancing adherence. The base is placed on a piece of broken pottery to help rotate it

while adding the coils.


Figure 7. Attaching the coil to the rim.

Once the coil is attached to the base, the bond between the two is sealed by using what

Swink calls a “horseshoe pinch” (2004:01). Using the thumb and forefinger, clay on both sides is

pinched and drawn down over the rim about one centimeter while the other hand supports and

rotates the vessel (Figures 8, 9). This creates a thick, welded joint. This joint is then blended and

smoothed creating a seamless juncture. It is sometimes possible to determine the number of coils

used in prehistoric pots by carefully feeling for the joints (Tite 1999:186).


Figure 8. Sealing the coil-rim joint.

Figure 9. Coil is attached and sealed.

The walls are built upward by placing the thumbs on the inside of the rim and the

forefingers on the outside, pinching and compressing the coils while rotating the vessel (Figure

10). The compression will create a rounded shape as the walls increase in height. To control the


shape one can apply pressure outward for bowls or inward for jars or canteens. The walls are

smoothed using fingers and scrapers (Figure 11). This also helps to further stretch and form the

vessel. Smoothing alternates with pinching and compressing. Additional coils may be added

depending on the size of the vessel.

Figure 10. Building the walls using the “horseshoe pinch”.

Figure 11. Smoothing the interior.


The final phase of construction is adding the rim. Before making the rim it may be

necessary to trim the lip using an agave thread so that it is relatively even. The rim is made by

gently pinching and smoothing the trimmed lip using a moistened forefinger and thumb to the

desired shape. Sometimes a thin rim coil can be used to create the rim, which was used by

prehistoric Puebloan potters (Swink 2004:106).

Once the vessel dries to a “leather state” where the walls are firm but yield to gentle

pressure without cracking (Jamison and Jamison 2007:43; Shepard 1980:370; Swink 2004) it can

be burnished and polished. When the vessel is dry enough where the clay does not stick to

fingers, a final smoothing can take place using moistened fingers, a smooth cloth, a scraping tool

or a smooth stone. Additional burnishing for luster can take place when the vessel is dry but

slightly damp using a dry, smooth river pebble (Figure 12). The friction of the pebble on the clay

walls physically compresses and aligns the clay particles to create a smooth reflecting surface

(Swink 2004:42). Different clays have different mineral properties that determine the degree of

luster that can be achieved.


Figure 12. Polishing and burnishing.

Painting and Design Elements

Painted wares in the Southwest appear in the archaeological record by Basketmaker III

(A.D. 500-700) times. Archaeologists have been partially successful in determining what was

used for paint. Striovia et al (2006: 1139-1145) used micro-Raman (µ-Raman) spectroscopy, a

noninvasive, nondestructive analytical method the uses laser technology to study the interaction

of light and matter, along with a scanning electron microscope, to determine the type of pigments

used on the pottery of the Ancestral Puebloans. The results of the analysis indicated manganese

was a principle constituent of some sherds, while others were carbon-based and probably derived

from plants such as the Rocky Mountain Bee Plant (Cleome serrulata) or Mesquite (Prosopis

glandulosa). Modern native potters use plant-based organic paints in the Four Corners region

(Swink 2004:197), and mineral-based paint in the Great Basin.

In some archaeological contexts it seems that there is a co-occurrence of beeplant pollen

with evidence of maize suggestive of an intentional encouragement and management of the plant

in prehistoric agricultural fields, particularly in northern Arizona and southwestern Colorado

(Adams et al 2002:351). A large Pueblo II village in the Cove-Redrock Valley in northeastern

Arizona had a large concentration of beeplant pollen, along with ceramic and stone scrapers in

three structures that were located adjacent to a trench kiln used for firing pottery (McVickar

1999; Smith 1999).

The Rocky Mountain Beeplant is native to the western half of North America from

southern Canada to northern New Mexico. It is an annual plant with a long (four to five-foot)

stem topped with pink, purplish, or white flowers and trifoliate leaves (Adams et al 2002: 341). It

can be harvested when it reaches full maturity in late summer and can be either used immediately


or dried and stored for later use. The plant has long been used as a natural dye, and has medicinal

properties. Why it fires to black on painted surfaces is still unknown. Some attribute the resulting

black color due to the plant itself being high in iron, which when fired, may break down to form

a black reduced oxide of iron and elemental carbon (Blair and Blair 1986:128). Shepard (1980)

and Stewart and Adams (1999) suggest that other mineral elements such as manganese or

hematite, when mixed with the paint, will produce a black paint.

The paint is made by filling a large stock pot with the stalks and leaves of the plant,

covering it with either rain water or distilled water, and boiling it for about six hours, adding

more water as needed (Adams et al 2002:349; Swink 2004:197-198) (Figure 13).

Figure 13. Making organic paint step 1.

The decoction is then strained into a smaller pot and then boiled uncovered until most of the

liquid has evaporated and begins to thicken (Figure 14). At this point, the mixture is stirred

constantly to prevent it from scorching until it is very thick, dark, and resin-like. This will yield

approximately 1-2 tablespoons of paint (Figure 15). The paint is stored in an open container to


prevent decomposition. Once it dries, it become hard and resinous and must be reconstituted with

a little water before it can be used.

Yucca brushes are made by removing the leaf pulp with a flesher of bone, stone, or antler

(Swink 2004: 191-194). Sometimes the leaf is soaked for a few weeks in water to speed up

decomposition of the outer layers, which makes it easier to flesh. The leaf is first pounded to

soften the pulp and then scraped or retted with the flesher until the only thing that remains is the

soft fiber. Brushes of various thicknesses can be made and stored for later use.

Figure 14. Making organic paint step 2.


Figure 15. Organic paint.

Many prehistoric ceramics have a slip that has been applied to the pot before painting.

Slips are made from grinding untempered clay and combining it with water to produce a thin,

watery mix similar to milk cream or thin yoghurt. Slipping is done while the vessel is still damp,

prior to burnishing. Swink (2004:41) makes slips from montmorillonite clays and recommends

slipping when the vessel has set to a leather state. He uses wide yucca brushes or a soft piece of

cloth and applies 2-3 coats of slip, allowing the vessel to dry between coats (Figure 16). Once

dry, designs are painted on the slipped surface with a yucca brush (Figure 17).


Figure 16. Slipping.

The finished vessel is left to dry in the shade in a warm place which can take several days

or weeks, depending on environmental conditions. Drying in the sun is not recommended as the

vessel may dry too quickly and crack.


Figure 17. Painting with a yucca brush.

Firing

Thermal features used for firing pottery have been found in the Four Corners area where

trench kilns have been identified and documented. A trench kiln is a sandstone slab-lined

rectangular or ovoid trench that can measure anywhere between 1.45-8.6 m long by 0.8-2.0 m

wide by 0.10-0.63 m deep (Swink 2004: 281), and is based on measurements of 35 excavated

kilns in the Mesa Verde region. In 1973 Claudia Helm excavated a slab-lined trench thermal

feature located on Cedar Mesa in southeastern Utah (Brisbin 2009:119; Swink 2004:279); David

Purcell excavated 19 trench kilns in 1993, Mary Erickson reported three in 1996 and two were

reported by Patricia Lacey, Leigh Hunt, and L.B, Lacey in 1997. Joel Brisbin excavated nine

trench kilns in Mesa Verde in 1993 (Brisbin 2009: 120; Stieber 2000: 23-23; Swink: 2004:279-

280). Brisbin documented the stratigraphy of these features, which led to collaboration with Clint

Swink to recreate a trench kiln firing that resulted in a four-step firing sequence. In 1997 joint

efforts between potters and archaeologists led to the excavation of kilns and an experimental


firing of an actual kiln on BLM land in Mesa Verde National Park which has been nicknamed

“Camp Kiln” (Swink 2004:279).

Trench kilns appear to have been used in the Four Corners area beginning around AD

970 according to a tree-ring date obtained from a kiln that was recorded by Brisbin in 1993

(Swink 2004:280). Archaeological evidence indicates that kilns were located anywhere between

100 meters to 25 kilometers from the nearest contemporaneous settlements (Swink 2004:280)

and were situated along the edge or below the rim of mesas, or across drainages and parallel to

slopes (Brisbin 2009: 119). The positioning of the kilns made use of air current flow that took

advantage of predictable and steady breezes to feed the fire and helped to maintain consistent

firing temperatures. Kilns are lined by sandstone slabs angled outward at about 30º which may

facilitate air movement. Another motive for the location of the trenches was the availability of

fuel sources. The preferred type of fuel seems to have been a combination of pinyon and juniper

wood due to their high burning temperatures. This has been verified through the analysis of fuel

remains from prehistoric trenches (Swink 2004:282-283). Data gathered from experimental

firings at the Crow Canyon Archaeological Center and at Camp Kiln indicate that approximately

143 kg of fuel were consumed per square meter of kiln.

The analysis of kiln stratigraphy in the Mesa Verde region indicate that the lowest

stratum, the kiln floor, tends to be lightly oxidized sterile soil covered in a dense layer of carbon

(Brisbin 2009:120; Swink 2004:282). Some partially burned wood and ceramic fragments can be

found in this stratum. The next stratum consists of tabular blackened stone above which is a

charcoal/ash layer that can contain pottery. The uppermost stratum consists of soil with little

cultural material.


The firing process is a complex activity that entails a number of stages. A primary fire is

initially burned to create an even bed of coals that will provide a heat source below the

greenware vessels. The layer of coals needs to be at least six centimeters deep so as to provide

sufficient heat. Kiln reuse may produce deep layers of carbonaceous material.

Once the fuel has burned down to live coals, sandstone slabs are laid horizontally over

the top of the coal bed with spaces in between to allow heat and air passage. This phase is

referred to as “shelving” (Swink 2004:285). Greenware is laid on the slabs in a single layer and

allowed to heat gradually before building the secondary fire. This serves to drive off any

remaining water, carbonize the organic paint, and reduce iron in the slip, which creates the black

design for painted wares. Broken pottery is placed over the greenware to protect it from burning

embers from the primary fire above (Hayes and Blom 1996; Swink 2004).

The third phase consists of building a secondary fire over the kiln. Long logs are placed

across the kiln to create a crib for the rest of the fuel which is laid perpendicular to the logs. This

creates maximum draft in order to raise fuel temperatures and maintain radiant heat. Tinder and

kindling are then placed on top and ignited. This allows the fire to spread slowly which reduces

thermal shock. Optimum temperatures are reached when the secondary fuel has been reduced to

an open bed of coals 6-10 cm thick. The goal is to generate enough of a high heat to vitrify the

clay, but if the fire is too open the fire will be cold and oxidizing. The ideal temperature to vitrify

clay is between 800-900ºC for 30-45 minutes (Swink 2004:293). Heat in excess of 950ºC can

create warping and cracking because the gases that were produced from the combustion of

carbonaceous material in the clay are sealed into the vessel walls.

The fourth and final phase of firing occurs when peak temperatures are reached and the

fuel has burned down to a bed of coals at which point the fire is smothered with a layer of soil.


This eliminates the air from the fuel and pottery and halts further oxidation, and allows the

pottery to cool slowly. Timing is crucial; the pottery must be allowed sufficient oxidation in

order to burn off residual carbon on slipped wares leaving them light gray to white, while at the

same time creating a reduction atmosphere so that the carbon in the paint will turn black.

Improper firing or preparation of the clay can result in warping or cracking of the pottery.

Vessels which are oxidized are those that have been exposed to too much air either during

cooling or during firing, and in painted wares can yield yellow to red color designs rather than

black. Oxidation can occur as a result of under-fueling or delayed smothering (Swink 2004:293).

Another effect of under-firing is pottery that is soft and dark. This can happen if too much

secondary fuel is used which can smother the coals nearest the pottery and result in lower

temperatures.

The following research design was developed on the basis of all of the procedures

described in the earlier sections of this paper and is the culmination of over two years of

preparation and study.

RESEARCH DESIGN

As stated earlier, this study was undertaken with the goal to successfully replicate

prehistoric Southwestern pottery for the purpose of better understanding the entire process in

detail, and to gain insight that could lead to future research. In preparation for this I participated


in a workshop offered by Clint Swink, an artist with a degree in wildlife biology who currently

lives in southwestern Colorado at the edge of the San Juan National Forest. Swink has over

twenty-five years experience replicating Mesa Verde and Maya pottery. He learned his craft

from a Hopi woman he refers to simply as “Mama”, no doubt in order to maintain her privacy

(Swink 2004:5; personal communication 2011).

Swink has collaborated with archaeologists on a number of projects, including the

excavation of an actual Anasazi trench kiln and the subsequent experimental firing of replicated

pottery in that kiln in partnership with the Bureau of Land Management (Swink 2004). In 1994

he was invited by the National Park Service to conduct an Anasazi pottery firing on Mesa Verde

as a demonstration at the 69th

annual Pecos Conference. Among his many achievements he has

reproduced Mesa Verde pottery that is currently on display at the Chapin Museum in Mesa

Verde National Park, and for the White House. Many archaeologists have taken his pottery

workshop, among them Margaret Lyneis, emeritus professor at the University of Nevada, Las

Vegas (personal communication 2011), and Karen Harry, also a professor at UNLV.

In an attempt to be as authentic as possible, I made several scrapers out of coconut shell

which are lightweight and easy to use. Since agave is widespread in my area, I was able to

fashion brushes out of agave fibers. A good working surface was made by stretching canvas over

a flat board however indigenous people may have used flat stones such as sandstone as a

working surface. One of the advantages of using a stretched canvas top is that it can be

moistened so that the rim of the vessel remains moist while the body is firming up in preparation

for attaching coils. Among the variety of tools I used I also had some obsidian flakes and bifaces,

some marine shell, the edges of which were ground and smoothed, and some squash gourd

scrapers. Finally, I was given some Rocky Mountain Bee Plant by Dr. Karen Harry which I made


into an organic paint and also made paint brushes from Yucca harrimaniea, or the narrow-leafed

yucca that grows in my front yard. I went on many clay procuring expeditions which is described

in the next section. I also made a sandstone-lined trench kiln in my backyard that measures

121.92 cm by 76.2 cm, and is 30.48 cm deep.

Clay samples

The raw clay used in this study was collected from several locations throughout Southern

Nevada and from the Arizona Strip. A total of five samples were collected and processed:

Sample 1, called “95 White” was collected along the State Highway 95 corridor,

approximately 19.1 miles northwest of Tonopah, Nevada (Figure 18). This locus is centered

within a cluster of geological associations, including the Youngston-Playas association, the

Gynelle-Cyrac association, and Zaba very gravelly loam (USDA Natural Resources

Conservation Service 2013), all of which are characterized by alluvial or lacustrine landforms

consisting of silty-clay loams (Figure 18, 19). This clay is fine-grained and white to yellowish-

white in color. The texture of this sample when wet is satiny to unctuous, an indication that the

clay is of good quality and highly plastic.


Figure 19. Sample 1: 95 White clay site.

Figure 19. 95 White clay site.

Sample 2, called “Cedar Pocket” was obtained from a small vein in a river terrace above

the Virgin River, located in Cedar Pocket within the Arizona Strip (Figure 20). The clay is red-

95 White clay

site


brown to yellow brown and is also fine-grained. The area is defined as being part of the

Riverwash-Torrifluvents complex (USDA Natural Resources Conservation Service 2013) which

is characterized as a flood plain consisting of mixed alluvium (Figure 21). When wet, the clay is

very plastic, and is rolled very easily into coils that crack only slightly when bent.

Figure 20. Sample 2: Cedar Pocket clay site.

Cedar Pocket clay

site


Figure 21. Cedar Pocket clay site.

Sample 3, called “I-15 White” is coarse-grained white clay from a deposit located 6.8

miles north of the Valley of Fire exit along the Interstate 15 corridor in southern Nevada (Figure

22, 23). The area is characterized as Badlands consisting of alluvial fan remnants (USDA Natural

Resources Conservation Service 2013). The clay itself may contain a high percentage of calcium

carbonate. This clay is highly plastic and when wet is very sticky, which may produce a good

slip. It may also be used as an additive to improve the workability of less-plastic clays.


Figure 22. Sample 3: I-15 White clay site.

Sample 4, called “Cactus Spring Gray” is a fine, green-gray clay obtained from the

vicinity of Cactus Springs, Nevada (Figure 24). This locus is set within what is called the

Corncreek/Haymont association (USDA Natural Resources Conservation Service 2013), an area

of mixed alluvial fan remnants and lacustrine deposits (Figure 25). The soils in this area range

from silty loams to fine and gravelly sandy loams. The Corncreek component is described as

alluvium derived from limestone and dolomite over lacustrine deposits while the Haymont

component is described as a mixed alluvium. The texture of the clay when wet is slightly

unctuous with a satin feel, and is also highly plastic.

I-15 White clay site


Figure 23. I-15 White clay site.

Sample 5, called “Moapa Red” is a red-brown clay from the Moapa Valley. The area is

situated on a terrace west of the Muddy River, and is characterized as Badlands (USDA Natural

Resources Conservation Service 2013) consisting of alluvial fan remnants (Figure 26). The clay

itself was highly compressed, which resulted in thick, hard blocks of clay that had to be slaked

before it could be processed (Figure 27). Slaking the clay entails wetting it to break it down into

finer sediments so that it can be later ground. Due to its location in the Moapa Valley, and its

proximity to several known archaeological sites, it is possible that this clay may have been used

by the local indigenous population to make pottery. A mineralogical analysis of both the clay and

local pottery is needed to determine this. An old U.S. Department of Agriculture report names

the soil as one among the Redfield series, of which there is fine sand, loam, and clay (Youngs


and Carpenter 1928:59-62). Redfield clay is described as being “…a brown to pale red soil that

occurs mostly on the west side of the lower valley on alluvial fan slopes”. It is a silty clay

comprised of a lightly crusted surface with a subsurface mulch overlying a hard, compact layer

followed by pale red fine sand. Deeper layers are characterized by reddish-brown to red clays,

with as much as 3% soluble salts. The clay was reported to be suitable for making pottery.

Figure 24. Sample 4: Cactus Springs clay site.

Clay Site


Figure 25. Cactus Springs clay site.

Figure 26. Sample 5 : Moapa Red clay site.

Moapa

Red clay


Figure 27. Moapa Red clay site.

The wet and dry color of each sample was identified and recorded using the Munsell soil

color chart (2009) (Table 1). Clay color is dependent on the types of impurities present in the

matrix, namely, organic matter and iron compounds (Shepard 1980:16). Clay that is free from

impurities generally appears to be white, while organic matter can impart a color that ranges

from gray to black. The presence of carbon can make some raw clays appear quite black, but will

fire white because the carbon is burned off (Swink 2011, personal communication). Red, brown,

buff, and yellow clay may contain hematite and hydrated forms of ferric oxide, while compounds

that are not fully oxidized may produce gray. Greenish clay may contain iron in the ferrous state;

iron that is in a lower oxidation state (Shepard 1980:16).

Table 1. Color and Texture of Clay Samples


Sample # Texture Munsell Color Observed Color

Dry Wet Dry Wet

1 fine, silty sticky, unctuous 2.5 Y 8/1 10 YR 6/3 buff

2 fine, silty grainy, unctuous 5 YR 4/4 5 YR 6/6

brown/red-

brown

3 coarse, grainy grainy, sticky N/9 N/ 9.5 white

4 grainy grainy, satin

Grey 1

7/10Y 5 Y 5/2 green-grey

5 grainy satin 7.5 YR 6/3 7.5 YR 5/4 red/red-brown

A sandstone slab was used as a metate and several river cobbles were used as manos to

grind each sample to a size that was less than one millimeter in diameter. Each sample was sifted

through a fine, food-grade screen with a one-millimeter mesh. The sample from the Moapa

Valley had to be soaked before grinding (Sample 5) because the compression of the terrace from

where the clay was obtained made the material rock-hard and extremely difficult to grind. By

adding enough water to moisten the clay and storing it in a sealed plastic tub for several days, it

began to break down into a finer, more workable state. The moist clay was then set out to dry in

the sun before grinding.

The method used to determine the amount of natural tempering present in each clay

sample and the amount of additional temper to add to each sample has been described by Clint

Swink (personal communication, 2011). This entailed preparing several clay discs without added

temper, each measuring approximately 7.5 cm in diameter by 1.4-1.6 cm in thickness (Figure

28). A five-centimeter line is etched across the disc. When the disc is completely dry, the line is

re-measured and the resulting number is divided by the original measurement (5 cm) (Table 2).


Figure 28. From left to right: Moapa Red, Cactus Springs Gray, Moapa Red and Cactus Springs

Gray combination, Muddy River Brown (not used in study), I 15 White, 95 White, Cedar Pocket.

Table 2. Degree of Natural Tempering in Clay Samples

Sample

Line Length in

Wet Clay

Line Length in

Dry Clay

Percent of

Shrinkage

1 5 cm 4.8 cm 4%

2 5 cm 4.75 cm 5%

3 5 cm 4.5 cm 10%

4 5 cm 4.0 cm 20%

5 5 cm 4.3 cm 14%

Several materials were used as temper: sand, crushed basalt, and crushed pottery. Each of

these types of temper has been used extensively by prehistoric peoples in the American

Southwest. The sand was obtained from the Moapa Valley and was of two types: one was the

fine-grained red sand typically found throughout the valley, and the other was a fine-grained

gray sand. The basalt was the vesicular type and was hand-ground and sifted through the same

mesh as the clay. Several batches of clay paste were made using different quantities of temper

and were stored in plastic bags to allow the clay to cure (Table 3). All batches were stored for a

minimum of one month.

Table 3. Prepared Clay Samples


Batch # Date Clay Type Quantity Color Temper Quantity

1 9/2011 Moapa Red 90% Red-brown Sand 10%

2 2/12/2012 Moapa Red 80% Red-brown Sand 20%

3 2/17/2012 Cactus Spring Gray 80% Green-gray Sand 20%

4 2/27/2012 Moapa Red 60% Red-brown Sherd 40%

5 3/2/12 Moapa Red 80% Red-brown Basalt 20%

6 3/11/12 Cactus Spring Gray 80% Green-gray Basalt 20%

7 6/11/2012 I-15 White 90% White Sand 10%

8 7/11/2012 Cedar Pocket 90% Red-brown Sand 10%

9 7/12/2012 95 White 90% Buff-white Sand 10%

For sand and basalt-tempered pastes no more than 20% temper was used so that the paste

would remain plastic. Sherd-tempered pastes required a larger quantity of temper. According to

Swink (2004:23) Mesa Verde white wares were tempered with crushed sherd, and he

recommends using twice as much crushed sherd temper as basalt or sand temper.

MAKING THE POTS: A DISCUSSION

Over a period of four months I was able to successfully replicate several vessels using the

steps outlined earlier in this paper. These included eight bowls, four jars, and two mugs. The

measure of success was based on the making, drying, and firing of the pottery without it cracking

or shattering. Not all of my attempts were successful; five bowls and one mug cracked either

while being made or during the drying phase. None of the vessels shattered when fired.

A number of variables were recorded, such as the date of when the paste was made, the

amount of temper in the batch (Table 4), and the date when a particular vessel was made or

attempted. The outdoor and, when relevant, indoor temperatures and humidity were recorded to

ascertain whether these variables would affect the outcome of the replication process. All of the


batches of paste had been stored for no less than six weeks; one batch had been stored for seven

months.

Table 4. Vessels by Clay Type, Temper, and Percentage of Added Temper

Vessel

No. Clay Type

Temper

Type

Temper

Percent

1 Cactus Spring Gray Sand 10%


3 Moapa Red Sand 20%

4 Moapa Red Sherd 40%


6 Moapa Red Sherd 40%








14

Moapa Red and

Cactus Spring Gray Sand 20%

15 Cactus Spring Gray Basalt 20%

16

Moapa Red and I 15

White Sand 15%

17 95 White Sand 10%

18 Cedar Pocket Sand 10%

19 95 White Sand 10%

20 Cedar Pocket Sand 10%

Of all of the vessels that were attempted, a jar and a mug made from the Cactus Springs

Gray clay, with a 10% sand temper, were the most successful (Table 5). This paste had been

stored for seven months. Less successful were vessels that had a higher percentage of temper.

One Moapa Red batch had 20% sand temper and another batch had 40% crushed sherd temper.

Of the sand-tempered vessels only two bowls and one mug was successfully made, while the


sherd-tempered batch did not successfully yield a bowl. All of these pastes were moderately

plastic and cracked a lot while being manipulated and shaped.

A similar result was achieved with the Cactus Springs Gray batch made with 20% sand

temper. Of two bowls, one was successful as was a jar however, a mug cracked before being

completed. Another batch of Cactus Springs Gray had 20% crushed basalt temper and

successfully yielded one bowl but the paste itself was only moderately plastic and cracked

repeatedly while being made.

The batches made from the Cedar Pockets and the 95 White samples yielded more

successful results. Both batches were sand-tempered with 10% sand. All were highly plastic and

cracked little while being formed and had an unctuous feel while wet. Each yielded a bowl and a

jar. One of the bowls made from the 95 White clay batch did ultimately crack, but this was due

to human error rather than to the properties of the paste.

Another two bowls were produced by combining different pastes. One was made with a

paste that was 50% Moapa Red with 20% sand temper and 50% Cactus Springs Gray also with

20% sand temper. This successfully yielded a bowl however the amount of cracking was high

and the plasticity only moderate. The second bowl was made from a paste that was 70% Moapa

Red with 20% sand temper and 30% I-15 White with 10% sand temper. The end result was a

more plastic paste with very little cracking.

Three of the vessels were painted. Two of them were slipped with the I-15 White which

was too sticky to use as a paste. Of the two, one of them was a bowl made from the Cactus

Spring Gray with 10% sand temper batch and was further decorated by painting with the organic

paint I had made and the other was a jar made from the Cedar Pocket with 10% sand temper


batch that was slipped but not painted. The third vessel, a jar made from the 95 White batch of

clay with sand temper was painted.

Firing the pottery produced mixed results; while none of the vessels shattered and all

emerged more or less whole from the firing, the end product in many cases was less than ideal

(Figure 29-38). There were problems controlling the temperature of the fire. A pyrometer with

two thermocouples was used to measure the temperature. One of the thermocouple leads was not

fire resistant and melted during the firing. The other was fire resistant however the temperature

readings were not reliable. At one point the temperature registered 450ºC but was the reading

was taken after the fire had been smothered.

No Type Temp Humidity

Plasticity

(L/M/H)*

Cracking (when

drying)

(L/M/H)** Slip Painted Success


Table 5. Vessels by Type

1 Jar 83º 10% M/H L Yes Yes Yes

2 Mug 83º 18% M M No No Yes

3 Bowl 93º 14% M M No No Yes

4 Bowl 93º 14% M H No No No




8 Bowl 78º 17% M/H H No No Yes

9 Mug 78º 17% M/H H No No Yes

10 Bowl 77º 16% M/H H No No Yes

11 Olla 77º 16% M/H H No No Yes

12 Mug 75º 5% M/H H No No No

13 Bowl 75º 5% M/H H No No No

14 Bowl 75º 5% M H Yes No Yes

15 Bowl 75º 5% M H No No Yes

16 Bowl - - M/H L No No Yes

17 Bowl - 23% H No No No No*

18 Bowl - 23% H No No No Yes

19 Olla 92º 27% H No No Yes Yes

20 Olla - 25% H No Yes No Yes

** L= Low M=Moderate H=High


Figures 29-32. Top: Primary fire. Bottom: Shelving


Figures 33-36. Top: Setting the pottery on the shelves. Building the secondary fire, and

smothering.

Figures 37-38. Cool down and finished pots.


A closer look at each individual vessel after firing has provided some interesting insights

into the firing process:

Vessel 1: A jar made from Cactus Gray sand temper (10%) that was slipped with I 15

White and painted with black designs. It emerged from the kiln with half of the vessel

carbonized and the paint had turned a rust color, and the other half fired to a white color (the

same as the slip) and the designs fired to black (Figure 39). It is possible that half the vessel may

have become at some point over oxidized, which turned the paint a rust color rather than black.

The other half may have carbonized because of premature smothering, which may have

prevented the fire from achieving the proper firing temperature.

Figure 39. Vessel 1

Vessel 2: A plain, unpainted mug made with Cactus Gray sand temper clay. There was

some moderate cracking when it was being made however it was successfully fired. The clay


fired to a buff color, with spots that Swink calls “firing freckles” (2004:294) which are the result

of organic material in the smothering soil that comes into contact with the hot coals and smudges

the pottery. Half of the mug appears carbonized, which may be the result of a reducing

atmosphere due to premature smothering of the fire (Figure 40).

Figure 40. Vessel 2.

Vessel 3: A plain, unpainted bowl made from Moapa Red sand-tempered clay. The

amount of temper in the clay was 20% which produced a moderately plastic paste that was

somewhat difficult to coil. The bowl fired to a red-buff color.

Vessel 4: A bowl made with Moapa Red sherd temper that cracked while being made and

did not make it to the firing stage. Possible causes for the failure include too much temper in the

paste, high outside temperatures (above 75ºF), or increased humidity (above 10%) which causes

the clay to expand too much and makes it more prone to cracking. The amount of temper added

to the clay was 40% crushed sherd.


Vessel 5: A bowl made with Moapa Red sand temper that cracked while being made and


paste, high external temperatures (above 75ºF), or increased humidity (above 10%) which causes


to the clay was 20% sand.

Vessel 6: A bowl made with Moapa Red sherd temper that cracked while being made and


paste, high external temperatures (above 75ºF), or increased humidity (above 10%) which causes


to the clay was 40% crushed sherd.

Vessel 7: A bowl made with Moapa Red sand temper that cracked while being made and


paste, or increased humidity (above 10%) which causes the clay to expand too much and makes

it more prone to cracking. On this day the outside humidity registered at 21%. The amount of

temper added to the clay was 20% sand.

Vessel 8: A plain, unpainted bowl made from Moapa Red sand-tempered clay. The

amount of temper in the clay was 20% which produced a moderately high plastic paste that was

difficult to coil, possibly due to the outside temperature which registered 78ºF on that day. The

outside humidity was 17%. The bowl fired to a red-buff color.

Vessel 9: A mug made with Moapa Red sand temper. The plasticity of the clay was

moderate to high, yet it cracked quite a bit while being made. This may have been due to external

temperatures which registered 78ºF on that day, or it could have been the amount of added

temper, which was 20% sand. After firing the color turned a red/buff with a lot of smudging on


one half. This may be the result of over-oxidation because the fire did not achieve an adequate

temperature to completely fire the vessel.

Vessel 10: A plain, unpainted bowl made from Cactus Springs Gray sand-tempered clay.

The amount of temper in the clay was 20% which produced a moderately high plastic paste that

was difficult to coil, possibly due to the outside temperature which registered 77ºF on that day.

The outside humidity was 16%. The bowl fired to a buff color.

Vessel 11: a wide mouth jar made with Cactus Springs Gray clay of moderately high

plasticity that cracked frequently while being made. The outside temperature was 77ºF and the

humidity was 16% on that day. The jar was painted with black designs on the outside surface. It

fired to a buff color on the inside but the outside appears carbonized probably due to a reduced

atmosphere. The black designs fired to a rust color and in some places black color.

Vessel 12: A mug made with Cactus Springs Gray clay that cracked while being made

and did not make it to the firing stage. Possible causes for the failure include too much temper in

the paste. The amount of temper added was 20% sand.

Vessel 13: A bowl made with Cactus Springs Gray clay that cracked while being made

and did not make it to the firing stage. Possible causes for the failure include too much temper in

the paste. The amount of temper added was 20% sand.

Vessel 14: A bowl made from a combination of two different clays: 50% Cactus Springs

Gray with sand temper and 50% Moapa Red with sand temper. The amount of temper in both

clays was 20%. The bowl was slipped inside and out with 15 White clay. This combination

produced a moderately plastic paste that cracked a lot while being made for unknown reasons.

The bowl fired to a white/light gray color.


Vessel 15: A plain, unpainted bowl made from Cactus Springs Gray basalt-tempered

clay. The amount of temper in the clay was 20% which produced a moderately plastic paste that

was difficult to coil, for unknown reasons. The bowl fired to a buff color.

Vessel 16: A plain, unpainted bowl made from a combination of two clays: 70% Moapa

Red sand-tempered and 30% I 15 sand-tempered. The amount of temper was 15% and yielded a

moderately high plastic paste that coiled easily with little cracking. The bowl fired to a red/buff

color.

Vessel 17: A bowl made with 95 White sand temper that cracked while being made. The

cause for the failure was human error; not enough time was allowed for the preform to set so that

clay coils could be added without stressing the base and collapsing. The properties of this clay

were very good for making pottery; it was highly plastic with an unctuous feel that did not crack

while I stretched out the base. It might have made a fine pot had it not been rushed.

Vessel 18: A bowl made with Cedar Pocket sand-tempered clay. The amount of added

temper was 10% which resulted in a highly plastic, unctuous feeling paste that was easily coiled

and did not crack at all while being made. The bowl fired to a red-orange color on the inside,

while on the outside much of it turned a dark brown from premature smothering. In places it

appeared the same red-orange color as the exterior.

Vessel 19: A painted jar made with 95 White sand temper. The clay was highly plastic

and did not crack at all while being made. This could be attributed to the proper amount of

temper being added to the clay, which was only 10%, and to a lower outside temperature which

registered 74ºF on that day. After firing the clay turned a buff color but the paint turned a rust

color which may be an indication of over-oxidation during firing (Figure 41).


Figure 41. Vessel 19.

Vessel 20: A plain, slipped jar made with 95 White sand temper. The clay was highly

plastic and did not crack at all while being made. This could be attributed to the proper amount

of temper being added to the clay, which was only 10%, and to a lower outside temperature

which registered 74ºF on that day. The firing completely carbonized the exterior and interior of

the jar, which may have been a product of smothering.

Several discs were also fired. The external and internal color of each disc was recorded

after the firing (Table 6).

Table 6. Clay Discs after Firing

No. Clay Type Firing Color

External Internal

1 Moapa Red Red/Buff Red/Buff

2 Cactus Springs Gray Gray/Buff Yellow/Light Brown

3 Cedar Pocket Red/Orange Red

4 95 White Buff Buff


Several adjustments must be made for future firings such as better assessment of the

amount of fuel needed for primary and secondary fires, allowing the green ware to slowly heat

before adding the secondary fuel, and allowing the secondary fire to reach the optimal

temperature of 900ºC before smothering the fire. The results of this firing seem to indicate that a

combination of factors including excessive oxidation and premature smothering that increased

the time the vessels were subjected to a reductive atmosphere may have produced vessels that

seemed to be both carbonized and under fired simultaneously.

Spectographic and X-Ray Diffraction Analysis of the Clay Samples

An attempt to determine the types of clays that were suitable for making pottery was one

of the initial questions posed by this study. Five clay samples were submitted to the University

of Nevada’s Geosciences Environmental Soil Analysis laboratory for spectrographic and x-ray

diffraction analysis. Spectographic analysis is a method for determining the chemical

composition of materials by subjecting the atoms of the material being analyzed to different

types of excitation, including high temperature, strong electrical fields, or bombardment by

electrons (Shepard 1980:143). The electrons are knocked from inner orbits to outer orbits, and

back again, releasing energy in the form of light that can be viewed with a spectroscope. X-ray

diffraction is a means of studying the atomic structure of materials (Shepard 1980:146). Crystals

form three-dimensional gratings or diffractions that can be interpreted in terms of the atomic

arrangement of the crystal.

The samples that were submitted for analysis were the Moapa Red, Cactus Springs Gray,

I-15 White, Cedar Pocket, and 95 White clays. A preliminary report based on the x-ray

diffraction analysis yielded the following results:


Sample 1: 95 White mineral constituents include quartz, calcite, K feldspar (sanidine),

illite, merlinoite, and aluminum hydroxide.

Sample 2: Cedar Pocket mineral constituents include quartz, calcite, K feldspar dolomite,

illite, muskovite, and K feldspar (sanidine).

Sample 3: I-15 White mineral constituents include dolomite, quartz, gypsum, and some

illite.

Sample 4: Cactus Springs Gray mineral constituents include quartz, albite (plagioclase),

illite, muscovite, and gypsum.

Sample 5: Moapa Red mineral constituents include coarse grained quartz, illite, and

chlorite.

The spectographic analysis results were inconclusive but did imply that all samples had

relatively high percentages of silicon, aluminum, iron, and calcium. The samples will have to be

resubmitted for a more in-depth analysis at a later date. The mineral constituents and elements

present in each sample are compatible with the definition of clay minerals presented earlier in

this paper. In essence, all of the clay samples have properties that make them suitable for

making pottery. This is particularly relevant because of the implication that the prehistoric

peoples of the region had access to the necessary resources for pottery production. To confirm

this it will be necessary to identify and sample more sources of local clay, submit them for

analysis, and compare them to the pottery that has been recovered from archaeological sites in

Southern Nevada.

FUTURE RESEARCH


The replication of coil and scrape-style pottery has become the foundation for future

research in prehistoric ceramic technology. The entire process, from identifying and sampling

local clays, to processing and making a paste, as well as the frustrations and successes of

reproducing pottery, and last, but not least, firing the pots in a traditional manner, generated a

number of important questions:

1. Was pottery making a planned, seasonal activity or was it more informal? What

season was optimal for making and firing pottery?

2. Trench kilns have not been identified in Southern Nevada so how was pottery fired in

this region? Agave roasting pits are abundant and it is possible that some of these

features could have been used as kilns. More research in this area may reveal

important information pertinent to ceramic technology and firing.

3. What were the sources of organic paint in Southern Nevada? Was organic paint

imported or were local sources available? If so, what types of plants or other organic

materials were used to make paint?

4. What impact, if any, did sources of local clay have on settlement patterns or seasonal

rounds?

5. How do replicated vessels compare to archaeological specimens in terms of heat and

stress resistance? Does the choice of temper determine the type of ware produced?

Learning how to make pottery has been an eye-opening experience for me and has

created new possibilities for research and experimentation. Before becoming engaged in this

sometimes rewarding, often frustrating activity, I now look at pottery with a deeper

understanding of the challenges that native peoples had to overcome in order to produce the

diverse wares that were used in their everyday lives. My respect for these people has increased a


thousand fold and I hope to honor them by continuing to learn about this ancient tradition and

perfect the skills I have been taught so that I can pass this knowledge on to future generations.

ACKNOWELDGEMENTS

This work would not have been possible without the support and help I have gotten from

so many people over the last few years. Students from the College of Southern Nevada and from

the University of Nevada, Las Vegas have been enthusiastic supporters and have helped in

various stages of the pottery making process. Thanks to James LaFleur, Katie Hoffman, Michael

Denman, and Thomas Wambacht for accompanying me on several clay hunting expeditions over

the years and for getting very dirty and sometimes even wet. Thanks to Krysan Williams,

Courtney Causey, and Sandy Paytaryan for the back-breaking work of grinding clay and making

pastes. Thanks to Kara Osborne, Nancy O’Connor, Laura Lindersmith, Sean Magann, James

LaFleur, David Crane, and Michael Denman for the long, lazy afternoons in my living room and

in my backyard making some very interesting vessels (not all of them made it into the fire!).

James LaFleur, Mike Denman, Sean Magann, Krysan Williams, Sandy Paytaryan, and Courtney

Causey all helped to collect firewood, dig my backyard trench kiln, and fire the pottery; thank

you from the bottom of my heart! Samantha Rubinson and Rayette Martin from the Southern

Nevada State Historic Preservation Office very generously donated their time and effort in

helping me prepare clay for a workshop at the Nevada State Museum. Dr. Kevin Rafferty, my

fearless leader at CSN, has been unstinting in his support and encouragement for my work and

made it possible for me to purchase some very important tools needed in my research. A very

special thanks to Greg Seymour and Dr. Margaret Lyneis who pointed me in the right direction


when I was lost and who very enthusiastically supported me in my efforts to learn how to make

pottery. A very deeply felt gratitude goes to my husband, Paul Billings, who has been my rock

through all of this; he’s had to put up with clay dust and muddy hand prints throughout the house

and patio, finished and unfinished pots all over the house, with my tools lying around and clay

clogging up the sink. I wouldn’t have been able to do this without his support. Last, but not least,

to my teacher, my mentor, and my friend, Clint Swink, and his wife Rickie: thank you for

opening my eyes to a new world of possibility, for sharing your knowledge and opening your

home to me, for setting my feet upon the path of learning that will undoubtedly continue for the

rest of my career. I only hope that I can reach out to others and pass on your legacy and that of

the people who came before you with as much skill, patience, and humility as you have shown

me.


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EXPLORATIONS INTO PREHISTORIC POTTERY REPLICATION: A PRELIMINARY REPORT

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