An American bloomery in Sussex

Lee Sauder

Germinal Ironworks, 1365 Bird Forest Road, Lexington, Virginia 24450, United States of Americalee@leesauder.com

ABSTRACT: This paper describes two iron smelts both of which produced substantial blooms. The experience from these and other smelts is then used to reflect on the author’s Practical Treatise, including fundamental issues such as furnace construction, air flow rates and the inter relationships between slag and bloom.

Introduction

About a decade ago, my friend Skip Williams and I wrote a paper describing some of our experiences with bloomery smelting (Sauder and Williams 2002). At that time, we had run on the order of 30 smelts. We have now run over a 120 smelts, and I have smelted and forged well over a ton of bloom iron. So besides briefly describing the bloomery smelts conducted at the West Dean conference, I have been encouraged to use this opportunity to provide an update on some of what I have learned since that last paper. I also intend to briefly point to new directions for my work, some of which were inspired by my trip to the conference. Since the publication of our earlier paper (Sauder and Williams 2002), we have grown a small network of smelter/smiths who try to gather annually for an extended experimental campaign. Among these friends are Steve Mankowski and Shel Browder, of Colonial Williamsburg, who accompanied me on this trip.

Experiment descriptionThis experiment was designed mainly as a demonstration rather than as an experiment; ie a careful examination of the effect of a change in variables. I find any public event to be a poor place to do a real experiment, since you can’t give the furnace your entire attention. So our idea here was to simply share our current working practice, and stimulate discussion. Of course, using an unfamiliar ore, clay, and air supply introduced plenty of new variables for one smelt!

Clay and oreWe arrived at the site on Monday afternoon, after a miserable and sleepless overnight flight from the States. This began the pattern of sleep deprivation that I followed for the next two weeks. Browder, having succumbed to the temptation of a lunchtime pint, then succumbed to the temptation of his new bed, while Mankowski and I mixed clay for the furnace. The clay body was mixed dry from sand, crumbled horse manure and some Imerys clay (see Phelps this volume, 161–168, for chemical analysis of samples of the mixed clay). We mixed the sand and manure in about equal volumes, and added as little clay, and then water, as possible in order to achieve a stiff but reasonably plastic consistency after vigorous mixing and kneading. We worked these into fist-sized lumps, and

allowed them to rest overnight, which greatly improves the clay’s workability.

After examining the various ores, we selected the Cumbrian hematite, since we knew we could get someone else to break it up for us. We asked the crew to break it up so that most of the ore ranged from the size of a sunflower seed to the size of a shelled peanut, to leave in the fines, and to sort out the white quartzy bits. Meanwhile, having roused himself from his brief slumber, Shel scrounged saplings and scrap lumber, and built a form for the interior of the furnace. This form was roughly 0.25m in diameter, with a slight taper to the top, and roughly 1.2m tall.

Furnace constructionWe began to build the bloomery on the Tuesday morning (Fig 1). This furnace design is not modelled after any particular historical or archaeological example, though it resembles many. It has simply evolved over time as a practical and useful bloomery. We first built a plinth for the furnace proper by building a ring of house-bricks centred on our furnace form. The inner edge of this ring was perhaps 150mm from the edge of the form. The first course of brick was laid flat, and the second on edge, for a total plinth depth of about 160mm. We packed the outside and interstices of the brick with the rough clay from the site to hold them firmly, and then filled the interior of the plinth ring with well-pounded charcoal fines, in order to create a firm base to build the furnace shaft on. The notions behind building this plinth are to give a nice dry base, to raise the furnace to a more convenient height for working, to facilitate slag drainage, and especially to make bloom removal much easier, with hope of leaving the furnace intact. Shel and Steve then repaired to the West Dean forge to make some smelting tools (bloom tongs, ore shovel, charcoal bucket, and various hooks, pokers and prodders) while I began building the furnace shaft.

The shaft was built by adding well-worked lumps of clay in a spiral fashion around the form. The target thickness of the furnace wall was about 60mm, which tended to slump more towards 80mm towards the base of the furnace. To control slumping, I cinched a girdle of twine around the shaft every 100 or 120mm as I built upwards. After I reached a final shaft height of almost a metre above the plinth, we added a buttress of clay around the base of the shaft, wide enough to

Sauder L 2013, ‘An American bloomery in Sussex’, in D Dungworth and R C P Doonan (eds) Accidental and Experimental Archaeometallurgy (London), 69–74.

ACCIDENTAL AND EXPERIMENTAL ARCHAEOMETALLURGY

70

catch the inner edge of the brick plinth. This constructiontook until dark. We then built a kindling fire around the outside of the furnace. After the outside of the furnace was lightly fired, we cut the tap arch and tuyère hole, and proceeded to burn out the form. We continued burning for a couple of hours, until the furnace was dry and no longer steaming, and the beer was gone.

Smelt 118: WednesdayThis smelt was intended as a warm-up and shakedown run for the experiment scheduled for the following afternoon. The morning was consumed by sorting out blowers and generator problems, setting our tuyère, and general set-up and housekeeping. For those who remain sceptical of our blowing rates, our preference would have been for a nice tight set of double chambered blacksmith’s bellows, but such was not available. So we used a vacuum fan with a variac, kindly lent by Roger Doonan. This blower fed a copper tuyère with a 20mm orifice that protruded about 60mm into the furnace about 200mm up the shaft. The tuyère was angled downwards at approximately 20°.

The tap arch cut into the base of the furnace the previous evening was almost as wide as the shaft interior, and as high as the tuyère hole. I clayed in this arch, leaving a narrower vertical tapping slot in the arch, just wide enough to sneak my hand into. I then filled the base of the furnace with more charcoal fines, and pounded them firm into a bowl shape 80 or 100mm below the tuyère.

We preheated the furnace all morning with a wood fire fed by natural draught through the tapping slot, while we sorted

out the fans and generators. A little after 2pm, we finally started burning charcoal with forced air, and sealed up the tapping slot.

We had measured out 28kg of ore for this smelt. We began charging at 2:57pm, with 0.5kg of ore added to the top of a full furnace. Thereafter, every ore charge was added to the top of the furnace so that it was distributed throughout the standard 2kg charcoal charge (roughly measured by vol-ume). The elapsed time to consume one of these charcoal charges is one of our main measures and controls of the progress of the smelt. In general practice, we would not alter the blowing rate significantly during the smelt, but would guide the temperature and charge time by adding more or less ore per charge, working our way up to a 1:1 ore to fuel ratio, or a little richer on the ore if the furnace acts like she’ll take it. Our intention was to work up to a smelting rate of 2kg each of ore and charcoal every 10 or 11 minutes. In this case, we were still working out our blowing rate as we charged. By our 11th charge at 5:32pm, we were charging 2kg of ore, and our fan was running at maximum, and our elapsed time was settling at about 12 or 13 minutes per charge.

At 6:58pm, we opened the tap slot and got our first run of slag, and at 7:12pm we added our last regular charge of ore. For the following hour, we kept the furnace full, recycling any slag that had a nice grey metallic, ‘high-wüstitey’ looking fracture, and adding more fresh ore on occasion. Our intention during this last phase of the smelt was to keep high-iron slag flowing through the bloom, and keeping things nice and hot and liquid in the bottom of the furnace. With the tapping slot open, we could now feel the face of the bloom

Figure 1: The first of the clay being added to the plinth and former for the furnace.

Figure 2: Probing the furnace (smelt 118) to check the formation of the bloom.

AN AMERICAN BLOOMERY IN SUSSEX

71

with a poker. By about 8:15pm, the face of the bloom felt nice and solid, and was reasonably filled in, and we were having trouble keeping slag flowing (Fig 2). We always try to pull the bloom before slag starts freezing up around the bloom too much and makes it difficult to remove. So we opened the tap arch, pried up the bloom to loosen it from the slag bowl, opened the front of the plinth and dug underneath the bloom a bit, and were able to withdraw the bloom without wrecking our furnace.

With the bloom still hot, we were able to cut it in half , and then one of the halves into quarters, with two sledges driving the bloom cutter. This bloom was not weighed at the time, but the (smaller) half that remains weighs 3.2kg. The entire bloom before cutting probably weighed about 7kg. The face of the bloom was still somewhat cup-shaped, having not entirely filled in, and on cutting it seemed nice and solid but perhaps a bit on the steely side (see Phelps this volume, 161–168). We can make a tentative judgement on a bloom’s carbon content when we hot-cut it; higher carbon areas of the bloom tend to be looser and crumblier, lower carbon areas denser and tougher. Hector Cole forged some of this bloom the following day, and it was indeed of mixed carbon content, with some iron areas and some quite steely spots (Fig 3).

Smelt 119: ThursdayThis smelt was the actual experiment for the first day of the conference. We made a few alterations to our smelt plan, in hopes of getting a slightly larger, denser, lower carbon bloom than the previous day. Those changes were to:

1) Set the charcoal bowl a bit higher in the furnace, so the bloom could start to fill in earlier,

2) Go to full 2kg ore charges sooner,3) Be more vigorous and attentive about slag tapping, to

make sure we got slag flow through the bloom and not just overflowing its edge,

4) Smelt a bit longer,5) Add some of the gromp from the previous days smelt.

David had asked us to shoot for a bloom removal between 4 and 5 o’clock, so I arose early to patch the furnace, refill the tap arch, and set the charcoal bowl before breakfast. Preheat with a wood fire began at 9:30am, and with charcoal at 10:30am. We pre-measured 34kg of the hematite. I also enlarged the intake on Roger’s fan, which improved its air delivery significantly.

We commenced with charging at 11:15am. With the improved air delivery, we were able to go to full 2kg ore charges by the 5th charge at 12:15pm, and the elapsed time settled quickly to our target pace of a nice steady 11 minutes per charge. We first tapped slag at 2:37pm and added our last regular charge to a full furnace at 2:44pm. At this point we had charged approximately 31kg of ore. We then allowed the stock level to drop in the furnace, to perhaps two-thirds full, and continued adding the remaining 3kg of ore, in no particular amount and with no particular schedule, until the end of the smelt. We also recycled some slag during this time. The idea behind dropping the stock level was to encourage slag production rather than reduction, in order to ensure a flow of decarburizing iron-rich slag on the bloom at all times.Of course, as soon as we tapped slag, the crowd of spectators

blossomed, things got very busy, and the note-taking pretty much ceased. Near the end of the smelt we also added several gromps from the previous smelt, adding them directly to the top of the bloom by reaching into the tap arch (with tongs, that is). But I do know that we removed the bloom at 4:30pm. This was held perhaps 30 or 40 minutes longer than we would have done, in order not to conflict with other experiments. Upon trying to remove the bloom, we found we had succeeded in smelting a larger bloom, perhaps too much so! It was rather difficult to extract, and the furnace suffered a bit of damage. The bloom birthing was also slow and laborious enough that the bloom was not quite as hot as we would like for cutting. It was also denser than the previous day’s bloom, so it was all we could do to get it cut in two; further quartering required reheating in the forge. Overall, this bloom did seem to have a lower carbon content, but still had a few steely spots. Again, this bloom was never weighed, and its bits were scattered amongst friends by the end of the conference. But I would guess it at 10 to 12kg.

Our first and foremost objective in a smelt is always to make iron, so it was a success in that regard. My previous experience with smelting hematite was fairly thin, perhaps 3 or 4 smelts, and I had found carbon control difficult in all those cases, so I was relieved to get two decent blooms. I only hope we succeeded as well in stimulating thought and discussion.

Figure 3: Cut blooms from Smelts 118 and 119 with example of forged bar and knife blade (forged by Hector Cole).

ACCIDENTAL AND EXPERIMENTAL ARCHAEOMETALLURGY

72

Update on the Practical Treatise

The experiment described above was intended to demon-strate some of the ways our working practice has evolved in the last decade (cf Sauder and Williams 2002). In general, our work has tended to go forward by going backward, util-izing more traditional furnace materials and construction. We did all our early work in a rather large furnace built of steel and modern refractory, with a water-cooled tuyère, and often with preheated blast. I think this may have led some to discount the applicability of our ideas to ancient smelting practice. But I still stand by all those ideas, and any changes and recantations that may follow are driven by my greater understanding of the working qualities of the bloom iron, rather than the use of more traditional materials.

Our current work tends to use a smaller clay furnace, with a copper tuyère, and occasionally using bellows for air supply. This is not just the result of curiosity or an urge for authenticity, but practicality as well. Clay has the tremendous advantages of being inexpensive, easily alterable, and almost endlessly recyclable and reusable. Compared with modern refractories, clay’s combination of insulative, reflective, and emissive qualities also seem much more suited to the bloomery furnace. All of which I suppose should have been self-evident, since the technology evolved in clay furnaces! But we’re all a bit susceptible to the hubris of modern man’s technical prowess, aren’t we? Most importantly, the use of clay has allowed us to easily and cheaply explore many different furnace designs. The size of the furnaces has shrunk, with the usual goal of producing a bloom of 8 to 12kg. This simply reflects a retreat from the usual Yankee madness of “bigger is better”. An 8 to 12kg bloom is just more pleasant to work on than a 20kg one.

The early furnaces were designed to be dismantled to remove the bloom, or to have the bloom removed through the top. Once we began using clay, though, we quickly converted to removing the bloom through the bottom of the furnace, by digging away enough below the tap arch to allow the bloom to be pried free.

Our use of the copper tuyère was first inspired by descriptions of its use in the Catalan furnace. We have stuck with it as it is extremely durable, convenient, and safe (the water-cooled tuyère caused our worst injury to date, knock on wood). The key to its durability is its conductivity. It simply needs to be long enough that the cooling effect of the air blast can keep the temperature of the tip from rising to an orange heat.

Though most of my own smelts continue to use a vacuum blower for an air source, I have successfully used hand-powered bellows on occasion. All of Shel and Steve’s smelts at Colonial Williamsburg have relied on bellows, and all their successful smelts have been conducted along the lines of the experiments described above.

In the discussion section of our earlier paper, we argued for a different view on three aspects of bloom smelting: air rate, slag management, and the recycling of furnace products (Sauder and Williams 2002). In the early days of our bloom smelting, our goals tended to focus on the yield of the smelt. In the years since, our focus has shifted towards the quality

of the resulting metal. This is a much more delicate, difficult, and complicated realm, and that has altered my view a bit on some of those issues.

Air rateSkip and I had proposed an air rate of 1.2 to1.5 litres/min/cm2 of furnace area (Sauder and Williams 2002). This may be excessively quantitative and specific, but I still maintain that if you’re not getting the results you desire, blow harder. Over the years Skip and I have helped a number of frustrated people get their first good bloom, and find that people commonly fail for one or more of three reasons: they’re not blowing hard and hot enough, they’re using bad ore, or they’re stopping the smelt too soon (ie not charging enough total ore).

Another aspect of air rate we mentioned before, but which was perhaps poorly expressed, is that low air rates tend to produce a high carbon product, and high air rates tend to produce low carbon product. Many people still think of this the other way around, but my experience has shown this time and again. There are, of course, many other factors that affect carbon content, which I’ll address briefly below. Since reasonably accurate measurement of air rate is a slippery business, we realised some time ago that it’s more sensible to measure the rate of charcoal consumption, as this is really a much easier, direct and more accurate measure of the air entering the furnace (though even this is complicated by the oxygen content of the ore). As noted above, we usually measure this as the time needed to burn a 2kg charcoal charge (or actually, at home, a 4lb charge). As I dig back in my notes from several very different furnace types, the optimum rate of charcoal consumption works out to a range of from 0.3 to 0.4g of fuel/minute/cm2 of furnace area. I am struck by the fact that the optimum rates we’ve used in each furnace, for high quality blooms, seem to all work out close to 0.35g/min/cm2.

Slag as a physical, chemical, and thermal resourceAh, now we’re getting down to the nitty-gritty! I still stand by our previous assertions, but we have learned so much more here. I see slag chemistry as the key to the working qualities of the metal, both directly and indirectly. Directly, in that if you end up with an iron-depleted slag in your bloom, you have a metal that welds poorly and fractures easily, and is in general, just difficult to work. Indirectly, in that the chemistry of the slag bath during all stages of the smelt is the key to the bloom’s carbon content. In short, I don’t think it’s too bald a statement to say that low-iron slag = bad metal, and high-iron slag = good metal. We judge the iron content of the slag by observing its behaviour upon tapping, and by examining its fracture. We strive for a free-running slag that on freezing, piles up on itself nicely. On fracture, we want to see a grey metallic sheen we refer to as ‘wustitey’, and a certain shape of fracture surface I don’t believe I could describe meaningfully. I often see comments in the literature equating very high iron content in archaeological slags with inefficiency on the smelter’s part. Rather, from my point of view, a high iron content in the slag would point to mastery of the process. If one’s goal is low-carbon iron that forges well, it is important to err on the side of leaving too much iron in the slag, rather than too little.

AN AMERICAN BLOOMERY IN SUSSEX

73

Recycling grompsOK, time to recant. I have found that the recycling of gromps has a deleterious effect on metal quality, so I have largely abandoned the practice. In several smelts I have made entire blooms largely of gromp, to make a second (or even third) bloom in a hot furnace. These gromps were charged, or even placed directly in the hearth, with fresh ore to make a nice iron-rich slag bath. Though these blooms were dense and lovely to look at, they invariably have resulted in a nasty and recalcitrant metal. Though there may be a good method of reprocessing this metal, simply adding it to the ore charge of a bloomery smelt is probably not it.

On quality controlI have a long way to go to be able to claim any mastery here, but I may as well take this opportunity to share some things we’ve found so far. It seems to me that the working quality of my blooms is largely determined by the control of three (interrelated) factors: slag chemistry, carbon content, and phosphorus content.

Slag chemistryI’ve covered this above, but in addition to the iron content of the slag, there are also things we definitely want to avoid getting into the slag. Too much alumina, from melting furnace wall, can cause a slag that makes for poor welding. To avoid this, we try to build our furnaces with thin walls to shed enough heat to keep the clay from melting and slagging too much, especially trying to keep it thin in the hot zone around the tuyère. Also, a clay mix that includes plenty of silica ensures that any slag that does form has reasonable melting temperature. The addition of too much calcium, added in an attempt either to increase yield or to control phosphorus, also seems to cause welding problems. I think I perceive trouble from this even if the slag viscosity during the smelt seemed fine, and the carbon content of the bloom has stayed low.

Carbon controlSome of the more important factors we’ve identified as affecting carbon content are air rate, slag chemistry, fuel:ore ratio, tuyère angle, and type of ore. Air rate and slag chemistry we’ve covered above. The effect of fuel:ore ratio is pretty straightforward and widely understood. Our general charging practice stays pretty close to a 1:1 ratio, and we’ll push it as heavy on the ore as we can, especially during the latter stages of the smelt. We’re rarely able to get much higher than 4:5 fuel:ore ratio without knocking down the heat in the furnace.

Steeper tuyère angles promote higher carbon contents. Tuyère angle has a lot to do with the shape of the bloom, and the depth at which it forms, both of which affect carbon content. The best angle varies with each furnace, but generally seems to hover in the area of 15 to 22°.

My experience with ores beyond my usual limonite are limited, but it seems that very rich ores really want to make steel. I also suspect ore of a very regular size, such as magnetite sand or hematite sandblasting grit, tends to make steel. I think a variety of sizes in the charge helps ensure adequate slag formation, since the different sizes travel through the

stack at different rates, some reducing in the stack more than others.

Phosphorus controlIt took Skip and I a long time to realise what a significant factor the phosphorus content of our ore is. And it’s taken us even longer to start to get some degree of control over it by any procedural means beyond ore selection. Since we have basically no access to any modern, professional analysis, we have been judging our phosphorus content by working properties and a bit of hillbilly metallography. We are still very much in the midst of working through this, but here’s what we think so far. Much of this work has been through collaborative effort with our ‘smeltfest’ crew.

Once again, the air rate/temperature/tempo of the smelt seems to have a large effect. Too slow a tempo produces a higher carbon, or worse, a carbon-phosphorus combination that doesn’t want to work up easily. Too high an air rate/tempo seems to raise the phosphorus content of the metal — enough to cause cold-shortness. So a medium tempo seems best — not adagio, not presto, but andante.

In terms of manipulating phosphorus content through slag chemistry, the addition of calcium seems to be a poor choice, for the reasons mentioned above. The addition of manganese ore to the mix shows more promise in this regard. Don’t ask me why, but manganese seems to make a pretty radical improvement in metal quality.

One thing I’d like to note is that from a smithing perspective, phosphoric iron is a really good thing. It makes for an iron that is dense and tough but forges beautifully. Some of the highest phosphorus blooms forge so beautifully it’s hard to believe there could be anything wrong with them when they’re cold!

The ‘Goldilocks’ principleAll the foregoing points to a consistent theme. The key to making quality iron seems to be a matter of finding balance. Not too hot, not to cold. Not too fast, not too slow. Not too much, not too little. Just Right.

A related observation is that success in smelting is built of careful attention to small incremental steps. It’s easy for two or three small overlooked details to compound into a big problem. So it pays to attend to every aspect of the job as carefully and thoroughly as possible. This requires plenty of time. Work up your ore, charcoal, and repair clay in advance, make any tools you need, and generally give yourself the time and space to pay attention. This really emphasizes the importance of a long, sustained working practice applied to any attempt to understand early iron-making technologies. Short and scattered experimental campaigns, with a different furnace and different ore every time, can cause more confusion than enlightenment, if they don’t find and explore that sweet spot every furnace has.

Forge it now!One extremely simple (and therefore easily overlooked) key to producing good iron is to forge it immediately, fresh and hot from the bloomery. No matter how long you try to

ACCIDENTAL AND EXPERIMENTAL ARCHAEOMETALLURGY

74

Figure 4: The Shizzle. Bloom iron figure in mild steel setting (by the author).

ManganeseAs I mentioned above, addition of manganese ore to our charge has a pretty dramatic effect on the resulting iron. So much so, that this is the only thing I’ve ever considered keeping as a trade secret — but I’m just not that kind of guy. I assume this is a matter of slag chemistry only, but I have no idea what’s really going on here.

Tapping regimeImmediately after the conference, I had the opportunity to help begin an excavation of a medieval bloomery site that Jake Keen located. Most of the bloomery slag I’ve seen in my life was made by me. Here I had a week to ponder the slag produced by someone with real mastery of the craft. I was struck by its density, the size of the slag flows, and the incredible consistency of it from one piece to the next. Though for years I have been trying to ensure a constant flow of high iron slag across the bloom, this medieval slag seemed to be telling me that I was being too timid in this regard. On returning home, I tried to smelt to reproduce the slag I saw by tapping more heavily and more often, and continuing with fresh ore charges rather than recycling slag. This smelt produced one of the most remarkable blooms yet, in terms of iron quality. All my smelts since have reinforced this lesson.

Re-meltingTo date, we have mostly refined our bloom iron by means of folding and welding. I am currently very curious about the possibility of refining the iron by re-melting, not to produce steel but to make soft iron. This is described explicitly by Evenstad (1968), and more obliquely by others. Are we overlooking an entire step in the ironmaking process?

I guess it’s time to quit writing and go find out.

AcknowledgementsMy trip to this conference was an unrelenting joy. Thanks to David Dungworth for making it happen. Thanks to Steve Mankowski and Shel Browder for being such fine workmen and boon companions. Everyone at the conference was incredibly friendly and helpful, but for particular assistance and kindness I’d like to thank Thérèse Kearns, Ellie Blakelock, Loïc Boscher, Siran Liu, Matt Phelps, Tim Young, Gerry McDonnell, Roger Doonan, and Hector Cole. And very special thanks to my brother Jake Keen for being Jake Keen.

ReferencesEvenstad O 1968, ‘A treatise on iron ore as found in the bogs and swamps

of Norway and the process of turning it into iron and steel (1782)’, Bulletin of the Historical Metallurgy Group 2, 61–65.

Sauder L and Williams S 2002, ‘A practical treatise on the smelting and smithing of bloomery iron’, Historical Metallurgy 36, 122–131.

reheat a cold bloom in a hearth, it will never be as nice and hot through and through as it was when it came out of the furnace. And all that long slow time that you try to get a thorough heat on a cold raw bloom, you are altering its slag chemistry. So the metal you get from starting with a cold bloom will not be the same as metal you get starting from a hot one. Even a simple compaction and splitting of the bloom really helps reduce the time and fuel needed to reheat.

New questions and directionsWell, there’s enough of these to last several lifetimes, aren’t there? Part of what I’ve found so fascinating about working with bloom iron over the years is its unpredictability and irregularity. Lots of the sculpture I’ve made from it has been about exploring its failures and funkiness. But as I come to understand it better, I’m becoming most excited about the possibilities of really good bloom iron. I can see the potential to produce iron that is superior to currently available industrial steels for artistic forging (Fig 4). These are a few of the directions that seem particularly fruitful at the moment.

PhosphorusWe’ve still got lots to do here, not just in getting more control over the metal’s phosphorus content, but how best to exploit phosphoric iron’s characteristics: its forgeability, its hardness, its corrosion resistance.