A Review of Conservation Treatments of Waterlogged Basketry from the Northwest Coast of North America.

Dana K. Senge and Ellen Carrlee

Basketry artifacts fabricated from limb wood, spruce and cedar root and the inner bark of yellow and western red cedar have been found in water-saturated archaeological sites in the Pacific Northwest since the mid-20th century. These artifacts range in age from a few centuries to more than five thousand years old. While these materials retain their overall physical structure due to burial in an anoxic environment they are degraded on the cellular level. Experiments and treatments performed by archaeologists and conservators over the past 50 years have attempted to stabilize these degraded structures and minimize splitting, crumbing, and distortion of the woven structures as they dried. Many of these tests and treatments are published in out-of-print conference proceedings or remain unpublished inconservation lab records. This review of tests and treatments as well as a current condition assessment of several collections brings this information together for thefirst time and allows conservators and archaeologists specializing in these treatments to see the broader arch of success and failure of the preservation of waterlogged basketry materials.

Introduction [heading]

Water saturated archaeological sites, or wet sites, became part of archaeological excavations in the Pacific Northwest in the late 1950’s when the Biderbost Site in Washington State was excavated by the Washington Archaeology Society (Nordquist 1976) and Dr. David Rice (Phillips and Deep

2008). Artifacts fabricated from wood and plant based materials ranging from 200-5000 years old have been recovered from wet sites around the northwest coast region of the United States and Canada and have provided a window into the culture, tools, techniques and life of the aboriginal communities in the region. Materials recovered from these sites range include baskets, mats, clothing, house planks, spindle whorls and looms, tools, carvings, anddetritus from carving and processing materials.

These organic artifacts, fabricated from wood, limb, inner bark and root, commonly from western red cedar and spruce trees, as well as grasses, cherry bark and other plants, arepreserved in an anoxic environment created by the continuouspresence of water. In this environment deterioration of the plant celluar structure is slowed but not stopped. The water-soluble molecules, such as cellulose, are slowly removed from the structure either though slow bacterial removal or slow hydrolysis and are replaced with water molecules. When recovered from the burial environment the organic material of the object may look whole, but quickly proves delicate when handled. Individual segments of root orinner bark may be so deteriorated they can easily be mushed apart by fingertips or split into thinner components. Woven or twined artifact and segments are stronger despite the degraded nature of the individual elements, the structure itself acting to hold or restrain the materials from complete deterioration.

If allowed to air dry, these materials will split, check, curl and distort as observed in materials both thick and thin in controlled slow air-drying tests (Erling 1990, Senge2009) as well as air drying in an uncontrolled environment.

For at least fifty years conservators and archaeologists in the Northwest Coast region of the United States have been testing and implementing techniques to reduce the shrinkage and physical distortion of basketry during drying and to improve the stability of the material for long term

preservation. The purpose of this investigation into these treatments is to learn about different treatment techniques used, the current condition of basketry materials, and the overall success or failure of these conservation treatment techniques.

Background [heading]

In 1976 the proceedings of two conferences focusing on the preservation of waterlogged artifacts were published: The Excavation of Water Saturated Archaeological Sites (Wet Sites) on the Northwest Coast of North American (Croes 1976) and Pacific Northwest Wet Site Wood Conservation Conference (Grosso 1976). The papers published in these proceedings covered a range of organic materials, many discuss the treatments tested, immediate results and conclusions regarding the treatments of basketry material. These papers provide some of the only known documentation oftreatments of several of the collections examined during this research into past treatment solutions and current conditions of waterlogged basketry materials and will be described in later sections. In general they describe the transition of treating waterlogged materials with diluted vinyl copolymer adhesives to working with polyethylene glycol (PEG) as an impregnant. Throughout the research represented in the papers published in 1976 one reads the dissatisfaction archaeologists and conservators had with treatment methods.

Research into the use of the most popular impregnant, PEG, continued into the 1980’s and 90’s. Jo Ann Erling, a contract conservator working in Victoria, British Columbia, tested a wide range of concentrations of PEG and impregnation time when considering the treatments of materials from Water Hazard (DgRs30). While this testing remains unpublished, her research and images remain with thecollection housed at the Laboratory of Archaeology at the

University of British Columbia and with the Conservation Labof the Museum of Anthropology.

Vincent and Deborah Cooke worked with conservators from the Canadian Conservation Institute (CCI) to examine re-treatment options of basketry materials from Ozette currently housed at the Makah Cultural and Research Center in Neah Bay, Washington. They selected three basketry fragments to include in their testing process which incuded removing the impregnate, vacuum freeze drying the fragments and testing consolidation of the surface with Polyox and Parylene. They felt the consolidants improved visibility of woven design and the artifacts maintained stability after re-treatment (Cooke and Cooke 1994). When examined in 2009 the samples show some sheen from the consolidant materials but appeared stable for handling, exhibit and research afterfifteen years in their relatively stable storage environmentat the Makah Cultural and Research Center. The inner bark fragments exhibit some shedding of the delicate material.

In 1996 and 1998 conservators and scientists from the CCI presented and published their work with PEG treatments of waterlogged basketry materials and a study into the penetration of PEG into the inner bark of western red cedar (Grant 1996 Bilz 1998). In the treatments described in the 1996 article, ‘Conservation of Waterlogged Cedar Basketry and Cordage’, the basketry and cordage treated with PEG 400 was stabilized but somewhat brittle. Some of the pieces required additional consolidation with Parylene to be stablefor travel and exhibition. Research described in the 1998 article, ‘Treating Waterlogged Basketry: A Study of Polyethylene Glycol Penetration Into the Inner Bark of Western Red Cedar’, shows that the cellular structure of cedar inner bark is different enough from the wood that treating baskets with the same concentration and molecular weight of PEG as waterlogged cedar wood may not be the best course of action for stabilizing these materials. The research was performed on processed fresh inner bark. The results of these examinations were used to extrapolate how

PEG would enter the degraded materials from an archaeological wet site.

In 2006, the authors began to summarize the historic background of past testing and treatments in an effort to make informed treatment choices for the treatment of waterlogged basketry materials, and build on the experimentation published in the 1998 article from Bilz, Grant and Gregory. The following sections summarize these past treatments of basketry materials and how they have agedthrough visual and physical characteristics.

Historic Treatments [heading]

The majority of historic and current treatments of waterlogged basketry face the challenge of removing water from water-saturated cells without also losing the structural support the water provides in the degraded material. The treatment must also counteract the strong forces caused by capillary action and the high surface tension of water when water evaporates. Treatments have revolved around variations of slowly drying the materials orimpregnating the structure prior to slow drying to replace lost molecules, bulk the voids, and control shrinkage or deformation of the elements of the artifacts. Additional treatment methods have included consolidation of loose, dry,brittle material after the drying.

Early treatment materials and techniques included coating the surface with vinyl copolymer adhesives, such as Elmer’s or Plyamul, diluted with water, drying between two layers ofglass and impregnation with PEG at various molecular weightsin various concentrations and for various lengths of time. More recent published consolidation tests have focused on the use of Parylene and Polyox recognizing that stability had not been fully achieved in the earlier treatments. The physical characteristics of the treated artifacts ranges

from tan-colored, lightweight, brittle and dry on one extreme to dark brown, heavy, waxy, flexible, and slightly moist to the touch on the other extreme.

The treatments described in this paper were gathered from existing records of basketry materials from water saturated terrestrial sites in Washington State, British Columbia and Alaska. While anecdotal information about possible treatmenttechniques used have been relayed to the authors, distant memories can be mistaken therefore following summaries depend solely on the written record from both published sources and collection treatment records. Table 1 providesinformation regarding the basketry collections examined to develop this summary of treatments. There are many waterlogged archaeological sites that contained basketry materials throughout the region not sited in this table. These were not included if treatment information was unavailable or incomplete or if the authors were unable to view the materials.

[Table 1]

Air or Solvent Drying Treatments [Sub-heading]

In general the air and solvent dried materials are light, brittle, shrunken or misshapen (unless dried between two plates of glass), regardless of age and level of deterioration. [Figure 1] The basket recovered from the Castle Hill site is Alaska is an exception to this finding. The records for this piece describe it as not fully waterlogged when found. The basket was placed on a sheet ofPlexiglas in a refrigerator. After several years of debatingtreatment options, the piece was re-examined and discovered to be dry with basketry elements remaining flexible stable when handled. This result was attributed to the basket beingonly slightly damp and not water saturated when excavated.

The condition of the basket at excavation was only minimallydeteriorated.

Adhesive Coating Treatments [Sub-heading]

Several authors have published anecdotal information regarding treatment with a white glue, either vinyl acetate copolymer (VAC) or poly vinyl acetate adhesive (PVA). These include the archaeological sites of Ozette (Daugherty 1976),Hoko River (Croes 1976) and Biderbost (Nordquist 1976). Of these three collections only artifacts from Biderbost collection were found to exhibit this type of treatment. A few artifacts from Ozette and Hoko River were treated with aPVA adhesive before treatment solutions shifted to the use of PEG (Daugherty 1976 and Croes 1976). However no evidence of basketry with the characteristic sheen of white glue treatment or treatment records citing artifact numbers have been found by the authors in either the Ozette or Hoko Complex collections. All of the materials from the Biderbostsite were treated with 25% Plyamul adhesive #9153 in Firewater, a heavy detergent manufactured by the Firewater Company of Los Altos. These were examined in 2009 and found to be rigid and firm with excess adhesive dried on the surfaces. The treatment was considered successful at the time since it minimized shrinkage and splitting of the material, however a contemporary assessment is that the treatment is somewhat crude with pools of adhesive on the basketry elements disfiguring the visual understanding of the material. In addition the Plyamul adhesive has proved slightly soluble in ethanol and not very reversible. The conservation material contaminates any samples taken from the treated artifacts, impacting potential instrumental analysis in research. The rigidity of the basketry materialsobserved might be due in part to the conservation materials and in part to the physical characteristics of original elements, which were thick sections of split limb, root and inner bark. Cross sections cut from the inner bark samples of Biderbost basketry were brittle and crumbled during

slicing; the root material was hard but maintained its structure during sectioning with a razor. Examination of a transverse section of the root material viewed under ultraviolet irradiation shows the adhesive along the edge and filling the lumina near the surface [Figure 2].

Polyethylene Glycol (PEG) Treatments [sub-heading]

During the initial seasons at Ozette in 1966 and 1967 the archaeologists realized that the white glue adhesive treatment was not an ideal solution. The effects of the adhesive were described as producing a stiff whitish lookingbasket (Daugherty and Croes 1976). This spurred the researchof Gerald Grosso into the possibilities of working with PEG to impregnate the structure and replace water molecules thatwould leave during the drying process. The goal of being tominimize damage to the material and loss of remaining form. Over the next several years he and Richard Daugherty looked at treatments developed in U.S. and Europe for waterlogged wood artifacts including the Vasa treatments published by Lars Barkman (Barkman 1962) and the treatments of waterlogged boats from Lake George, NY published by Seborg and Inverarity (Seborg and Inverarity 1962). From this research they tested a range molecular weights and concentrations to develop a method of volume processing these materials in the remote worksite of Cape Alva in orderto safely move the artifacts from the site to a workspace (Grosso 1976).

Around the same period other archaeologists in the region were inspired by the publications of Barkman and Seborg and also developed methods of working with PEG. As a result, in the 1970’s many basketry artifacts in the northwest coast region were treated with a range of techniques using PEG as a consolidant or impregnant. Treatments developed during this time period varied by impregnation time, molecular weight of PEG and concentration of the PEG in water. These variables in treatment, along with variables of material

types and level of degradation, resulted in a wide range of final results from tan-colored, lightweight, dry, and brittle to dark-colored, heavy, waxy, semi-flexible.

The most significant variable found in past basketry treatments in this region is duration of impregnation. Artifacts with short treatment times (1/2 day – 2 weeks) in medium to high molecular weight (1000-4000) PEG are generally dry in appearance and delicate to handle. The PEG appears to have aided in slow drying the artifacts and minimizing shrinkage and distortion, but did not truly penetrate the inner bark and root cellular structure leavingthe artifacts delicate to handle for exhibit and research. This is observed when examining a transverse section of material from the Conway wet site [Figure 3]. Basketry materials from Conway were treated by soaking in ethyl alcohol for 2 days and then placing in an impregnation bathsof 33% PEG 1000 in water for 2-4 days, followed by air drying. The cross section in figure 3 was stained with cobalt thiocyanate (Bilz 1998) and examined at 400x magnification with an Olympus BX-51 microscope under ultraviolet irradiation. The cobalt thiocyanate stain bonds to any PEG in the cellular structure and quenches the natural fluorescence of the lignin in the structure. Figure 3 shows that there was little to no PEG present in the cellular structure for the stain to bond with and the auto fluorescence of the lignin in the cellular walls is clearly observed.

Artifacts treated with a longer impregnation time and a blend of PEG molecular weights, such as the material from Ozette, are often dark brown/black, sometimes waxy in appearance and are slightly moist to the touch The main treatment method developed for the materials from Ozette wasa four week impregnation period with 50% PEG 1500 in water. PEG 1500 was renamed in the mid 1970’s to PEG 540 Blend, which is believed to be the same 540 blend that exists today: 41% PEG 300 and 59% PEG 1450. Transverse sections cutfrom a sample of western red cedar inner bark from the

Ozette material were pliable and PEG oozed from the structure when placed in a warm, humid environment. The inner bark material from Ozette disintegrated during the cobalt thiocyanate staining process, the material was too delicate to examine the level of impregnation of PEG into the cellular structure.

The 50% PEG 1500 impregnation method was an acceptable treatment method from many years. The disadvantages of thistreatment included weeping of the impregnant out of the structure, staining storage and exhibit materials in addition to limiting handling.

Additional refinement of the use of PEG in conservation occurred in the mid 90’s as conservators at CCI began testing treatment solutions and found a mix of lower concentration (20%) and lower molecular weight (400) and long immersions that provided a step towards a more desirable treatment outcome for many materials. The most current treatment technique is 20% PEG 200 or 400 raised in increments of 5% every 2 months for 8 months, then place in a bath of 20% PEG 200 or 400 plus 5% PEG 4000 for an additional 4 months. The basketry is then vacuum freeze dried until a stable weight is achieved (Eldridge 1997, Grant 2011). The goal of this method is to impregnate voids in the secondary cell wall with the lower molecular weight PEG and then bulk up the lumina of the structure withthe higher molecular weight PEG. The secondary bath with PEG4000 is considered an optional step, used for exceptionally friable material (Grant 2011).

Collections treated with this method exhibit a range of stability, due to material type and the level of deterioration of the material when recovered from the archaeological setting. Artifacts from the Ditidaht Sites (DeSf 9 and DeSf 10) are in stable but delicate, the Kanaka Creek basket (1992.004.001) is quite stable and robust, and the Scowlitz materials (DhR1-16W) are stable, but again quite delicate. The basketry materials from these

collections are very different from each other and were recovered from different conditions. The most robust are the basketry elements of the Kanaka Creek basket, these are thicker split limb elements, exhibiting little evidence of deterioration. The Ditidaht artifacts include baskets fabricated from inner bark materials and from split limb or root materials. The inner bark fragments are shedding fibers; the split limb/root materials are fairly stable overall. The Scowlitz basket fragments are fabricated from split limb. These are the most delicate of the limb/root materials and appear to be the most degraded of recent finds. Several of the Scowlitz pieces received consolidation treatment with Parylene. These pieces are light in color and appear fairly stable overall, the basketry elements were flexible and the surface spongy to the touch. However, the need to consolidate with Parylene (itself an experimental, last-resort treatment that does notallow easy re-treatability) suggests the PEG protocol alone was not enough for these materials.

The South Baranof Island Basket #1 from the Alaska State Museum was treated in 1994 with 20% PEG 400 and 5% PEG 4000 over the course of 6 months. Upon examination in 2009 the basketry fragments have a very natural-looking, pleasing appearance with no observable shrinkage or distortion, and the individual elements appear to have maintained some of their flexibility. However, the material is also very spongyto the touch, sheds fibers, and is too delicate for travel or exhibition.

Discussion [heading]

Conservators and archaeologists have been pursuing an ideal preservation solution for stabilizing waterlogged basketry materials for several decades. The past preservation treatment techniques for waterlogged basketry have been effective in preserving these materials for later generations. However, many of these artifacts are difficult

to handle and exhibit due to issues of stability or excessive conservation materials present. A successful treatment stabilizes the basketry weaving elements and allows for safe handling, transportation, exhibit and research with minimal loss of material.

From the start, air drying the materials has been recognizedas the least effective solution for most materials, resulting in artifacts that are brittle, deteriorate quicklyand often do not represent the original form of the object.

Many archaeologists and conservators also recognize that thecoating with adhesive treatment method is not fully effective. The only collection examined by the authors has rigid weaving elements, however this is more due to the nature of the thick split limb used in the basketry than theadhesive. Thinner elements were also stiff and rigid, innerbark elements exhibited some flexibility when handled, but disintegrated with cross sections were cut. The materials used in this treatment method sit on the surface of the structure, they do not penetrate the cellular structure to consolidate loose components nor impregnate and fill losses on the cellular level. The majority of testing and treatments over the past decadeshas focused on the use of PEG. PEG is used to replace the water from the burial environment and maintain the artifact’s form as it was recovered from the archaeological site. The variation of treatment outcomes with the same treatment methods is likely due to two issues: firstly, the variation of materials used in the fabrication of basketry and secondly, the variation of degradation of those materials.

The basketry elements most successfully treated by PEG tend to be split limb elements. These exhibit the least amount of degradation, they are commonly rigid after treatment, however, these materials also rigid in historic basketry. Finely split root basketry elements can be stabilized with

PEG treatments, but for the most part these finer materials exhibit a greater amount of degradation in comparison to thelarger split limb elements, and the impregnation treatment does not provide enough consolidative effect for these elements. These artifacts tend to need an addition step of surface consolidation treatment to be stable for handling and exhibit.

The least successful treatments of basketry tend to be of inner bark weaving materials. In general the inner bark basketry elements tend to be delicate, shed fibers with handling and, in some cases, are easily mushed apart betweenthe fingers. This can be attributed to the cellular structure of inner bark itself. The structure is very different from wood and degrades in a different manner than wood, limb and root elements. Basically, wood, limb and root elements loose water-soluble components of their cellular structure, initially seen in the secondary cell wall, but their overall structural grid remains [Figure 4]. Materials exhibiting greater degradation to their structuresinclude losses and damage to the primary cell walls, but again the overall structure remains [Figure 5]. The cellular structure of inner bark has layers of fat cell walls (phloem fibers) and thin cell walls (parenchyma) [Figure 6]. Depending on the level of degradation the network parenchyma and middle lamella holding the structure together is lost leaving the phloem fibers without a structure to hold them together. While a few fibers can be linked together in chains on the cellular level, the sectionof inner bark as a whole no longer has an internal structurefor the PEG to impregnate and support [Figure 7].

Other materials are used in basketry fabrication, such as grasses and cherry bark. To date, these have been treated in a similar manner as the limb, root and inner bark basketry materials. Very few examples were examined during the course of this research and conclusions about the treatment results of these materials cannot be summarized atthis time.

Current Testing [heading]

The conservation of waterlogged basketry materials is still a complex challenge and conservators in several labs are considering new variations of treatment solutions in order to improve overall physical characteristics of the treated artifacts. Refining the palette of treatment is ongoing through continuing research with low molecular weight PEG and more in depth research with high molecular weight PEG.

Over the past couple years Ellen Carrlee has been studying the conservation of spruce root with impregnation with high molecular weight PEG and the use of heat to increase penetration. Her latest results show samples of root treated with 55% PEG 3350 for 3 months created a stable robust material that has withstood the fluctuations of high RH. In addition she has been testing a wide range of consolidants for friable, delicate pieces already treated with PEG and has found promising results with Butvar B98. This research will be published in the preprints of the 2010Waterlogged Organic Archaeological Materials conference in Greenville, NC.

The deterioration of the cellular structure of inner bark ofwestern red cedar seen in Figures 6 and 7 may indicate that the basic strategy of using an impregnant to bulk up cell walls and possibly fill the lumina isn’t truly effective with this material. No doubt the PEG is aiding in preservation, possibly as a waxy consolidant holding the phloem fibers in the recognizable shape of inner bark than actually contributing the cellular structure. A new approach to these materials is under consideration. The phloem fibers of inner bark are similar to bast fibers used in rope found in shipwrecks and in fiber artifacts from other parts of the world, such as a neolithic shoe from Sipplingen (Wisner 2010). Initial testing comparing

treatment methods commonly used on bast fibers with treatment methods commonly used on inner bark is underway.

Conclusion [heading]

The examination of a range of waterlogged basketry collections of different ages and from different archaeological sites has provided an understanding of successful and not so successful conservation treatment methods implemented since the 1960’s. The success of the standard treatment method in use today still hinges on the level of deterioration. Current research into treatment variations that address the needs artifacts exhibiting increased levels of deterioration may help refine methods and allow for improved stability of those materials. The treatment of basketry fabricated solely of inner bark materials may need to be considered separately from the woody basketry materials. Again, current research may provide a variation of the current techniques that would address the specific needs of this material.

While a single all encompassing treatment solution is most desirable for volume processing of archaeological finds, recognizing major differences in material type and level of degradation, then applying treatment variations to accommodate for those differences may provide a large improvement for long-term preservation and access.

Acknowledgements (heading)

Many people provided access to collections and documentationthroughout this research. The authors would especially liketo thank Janine Bowchop and the Makah Cultural and Research Center, Laura Phillips, Megon Noble and Kelly Meyers and theBurke Museum of Natural History and Culture, Patricia Ormondand the Laboratory of Archaeology at the University of British Columbia, Katie Oliver and the Baranov Museum,

Martina Steffan, Kasey Brewer, Kjerstin Makie and the Royal British Columbia Museum, Grand Chief Clarence Pennier, DavidSchaepe and the Sto:lo Nation, Leona Sparrow and the Musqueam Indian Band, Nicci Bergunder and the Tsawwassen First Nation, Sven Haakanson, Jr, Ph.D., Tara Grant, Kitty Bernick, Jan Grosso, and Miriam Clavir.

Author Information (heading)

*Dana K. Senge, Conservator, Intermountain Region Museum Services Program, 255 N Commerce Park Loop, Tucson, AZ 85750. dana_senge@nps.gov

Ellen Carrlee, Conservator, Alaska State Museum, 395 Whittier St, Juneau, AK 99801. ellen.carrlee@alaska.gov

*Corresponding author

Table and Figure Titles:

Table 1. Collections of Archaeological Basketry from Waterlogged SitesFigure 1. Spruce root basketry sample, air dried. Sample made available by the Baranov Museum.Figure 2. Cross section of split limb from Biderbost site (45SN100-330a). Sample made available by the Thomas Burke Memorial Washington State Museum.Figure 3. Cross section of split limb from Conway site (45SK59b-72). Sample made available by the Thomas Burke Memorial Washington State Museum.Figure 4. Cross section of 2000 year old basket from Liyonmxetel (DgRm-1 basket 210). Sample made available by the Sto:lo Nation. (Basket remains un-treated).Figure 5. Cross section of 100 year old basket from Kodiak Island. Sample made available by the Baranov Museum.

Figure 6. Cross section of fresh inner bark. Sample provided by Sven Haakanson, Jr, Ph.D. Alutiiq Museum and Archaeological Repository.Figure 7. Cross section of 500 year old inner bark from Ozette (45CA24B70 30 III 2). Sample made available by the Makah Cultural and Research Center.

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