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Wrought Iron

I think artists and art enthusiasts alike stand to benefit greatly from a careful consideration of the materials used in artistic practice beyond their role as aesthetic vectors.

I have degrees in history, classics, and anthropology, and my academic background has instilled an appreciation of terminology as not only a descriptive tool, but also diagnostic. (I have also developed a bit of contempt for art history as a discipline, but I suppose that's another topic of discussion.) As a blacksmith and metalworker, often using traditional (sometimes archaic and anachronistic) tools and techniques, I sometimes get put off when people (through no real fault of their own) conflate worked steel and wrought iron. Drawing upon the modern ambiguity of what is commonly called wrought iron, I thought it would be interesting to take this particular material and examine what actually distinguishes it from other materials. What follows are some of my thoughts on the subject. I would appreciate any comments, questions, or parallel discussions of any favorite material of yours. Please disregard references to photos in the article; my original file had photos.

Despite its apparent ubiquity, materiality is a slippery topic. To date, most discussions of materiality among social theorists have in fact been evasions of it; they focus upon materiality as a social actor, as a semiotic object, as a mere surface or aesthetic conductor, or as a mediator of the transcendent (i.e., the immaterial). Materiality is often lost in the subject/object shuffle pervading western discourse, wherein agency is ascribed only to the subject, and the object functions as a passive receptacle of a script. But materiality is recalcitrant. The scripts need constant revision because materiality provides a finite number of affordances; all physical materials have their limitations. This recalcitrance makes materiality the wellspring of unintended consequences in the physical as well as social spheres; material is not, in fact, entirely passive. Materiality is stark reality; it is matter-reality which operates within the social milieu but independent of it. Materiality is a stone in our stream of consciousness: we think around it rather than through it, and our thoughts automatically conform to its shape. A careful consideration of the materiality of an object helps to construct a more complete understanding of that object in time, in space, and in culture.

In the spirit of Ingold, who promoted a hands-on engagement of materials as a more powerful method of analysis, here I consider one particular kind of material. I have studied this material and engaged with it professionally. The more familiar one is with a material, the closer she or he is to grasping (often literally) its materiality. But first, a proposition: In recognition that many materials are artifacts in themselves (i.e., plastics, alloys, and fabrics), I must reject the notion of a made artifact. For the purposes of this discussion, artificial materials do not exist, but rather all materials are modified from existing materials. Borrowing from the thermodynamic model, the Law of Conservation of Materials might therefore be thus: Material is neither created nor destroyed; it merely changes form. Similarly, as the entropy of the universe is always increasing (the Second Law of Thermodynamics), order only arises with an input of energy into the system. Therefore, in a material system, new materials are developed with an input of human agency. This move, though it may seem radical and counterintuitive, at once erases the nature/culture boundary so prevalent in material culture studies and situates all materials as equally material, no matter how much human agency and effort has been invested in their modification (rather than “production”). Any material maintains its recalcitrance and stark reality, no matter how specialized the modification process and no matter how much human agency is invested in its development or maintenance.

Wrought iron serves as an excellent example of a material which, through its intrinsic (or emergent) properties, resists the scripts imposed upon it by human agents and forces other social actants to modify their own practice. The term “wrought iron” signifies several types of object; etymologically, it refers to any iron or iron alloy which has been heated and shaped by human labor. But wrought iron as a material is a more specific term which is rarely differentiated in everyday parlance. Wrought iron as a material is a commercially produced (modified) low-carbon iron refined using either the bloomery or the puddling processes, containing slag and inclusions visible to the naked eye. This discussion is concerned with iron modified using the puddling process, as this process resulted in the particular examples of iron in the figures below.

The puddling process developed in 18th century England, and it was the first effective method of producing stable, relatively uniform, and tough iron on a larger scale than ever before (not since Roman times, with the wide use of bloomery furnaces, had as much iron, albeit of lower quality, been refined in Europe). It was vastly superior to other methods of iron refining at the dawn of the industrial revolution. Raw “pig iron,” iron bars resulting from the initial smelting process containing significant proportions of slag, sulfur, phosphorus, and other impurities, were first remelted in a puddling furnace. As the iron melted, the dense iron sank and the lighter elements rose to the surface. A master ironworker, called a “puddler,” then either tapped off the puddled slag or scraped it off the surface of the molten iron. Then, carefully watching the pool of iron and the color of the flames dancing across its surface, the ironworker gauged when to remove the refined iron with his long iron rod. The quality of the iron depended equally upon the intuition of the puddler and the initial purity of the pig iron.

When the iron had reached the desired consistency, the ironworker drew the iron out and handed the lump of iron to others to “shingle” it. Shingling is the process of hammering an amorphous lump of orange-hot wrought iron into a thick bar. This process squeezed out any large pockets of molten slag within the iron and force welded any gaps and fractures. The result was a bar of iron with very little carbon, strewn with longitudinal filaments of remnant slag formed in the shingling process. As desired, the wrought iron could be refined a second, third, or fourth time in order to remove more of the impurities, but some impurities would always remain.

Years of experience were required to produce suitable wrought iron; the iron puddler must have been able to judge how much pig iron to add to a charge, when to tap off the slag, and when to draw out the lump of iron. Furthermore, the correct size of the charge depended upon the particular furnace the puddler was using. Iron factories imposed strict requirements upon puddlers to maximize production, based upon the size of the furnace: puddlers were expected to extract the iron once it reached a specific mass, ranging from 50 to 100 kilograms. A puddler who extracted a kilo more or a kilo less on a charge would often be docked pay. Puddlers generally learned their trade through intense apprenticeships, and they formed a considerable portion of the residents in factory towns of the mid to late 19th century. They were respected as craftsmen and as men who possessed skills vital to the economy of the regions in which they resided. It was hard, hot work, but iron puddlers had comparatively secure and well-paying jobs.

The process of modifying pig iron into wrought iron was essentially a recipe of materiality. The material is specific because it exhibits very specific qualities which result from these processes. Its degree of hardness is one of the most important qualities, and it continues to be the primary quality which distinguishes old iron from new steel. Wrought iron is quite soft when compared to alloy iron and steel. It is an early result of attempting to arrive at pure iron. Pure iron was desired because impurities such as slag, phosphorous, and sulfur make iron weak. Soft iron is easily worked with hammer and anvil without stress fractures, and it can be twisted easily into intricate shapes when hot. Such a soft and tough material lends itself well to forming rivets and tenons, a major method of joining iron before the advent of electrical arc welding. The absence of carbon in wrought iron accounts for its softness.

The presence of carbon in iron causes the internal microstructure of the iron to form tiny crystals, transforming iron into steel. The higher the carbon content (up to 2% of the total weight of the material), the harder the steel and the stronger the crystals. Stronger crystals also make the steel more brittle and prone to fracture; compare to strong and brittle cast iron, with carbon content exceeding 2%. One can actually see the crystals of cast iron with the naked eye at the site of fracture. The softness of wrought iron due to its low carbon content also allows for a common test to determine whether a sample of material is wrought iron: the spark test. Because wrought iron is soft, it will produce sparks of a certain pattern and duration when subjected to a grinding wheel. Because wrought iron is soft, the grinding wheel removes larger pieces from the mass of iron through abrasion. These pieces, glowing from the heat of friction, form long streaks of light to the naked eye. Compare these streaks to those of high carbon tool steel: smaller pieces are removed, absorb more heat per unit of mass, and branch out into other sparks as the carbon is ejected from the hot steel flecks. These are the same type of branching sparks seen in handheld sparklers popular at summertime festivals.

Wrought iron contains less than .02% carbon, carbon steels contain between .02% and 2.1%, and cast iron contains between 2.1% and 4% carbon. Cast iron is much harder than wrought iron and steel, but it is quite brittle. Carbon steel is harder than wrought iron because of the crystalline structure, but it is also more brittle. The middle-range of carbon in steel gives it qualities which neither wrought iron nor cast iron possess: the ability to be hardened and tempered. A thorough treatment of hardening and tempering steel lies outside the scope of this discussion of wrought iron, so it will suffice to say that wrought iron cannot be heat treated to modify its hardness or toughness.

Figure 2 below shows a cross-section of a wrought iron rivet and several photomicrographs showing the internal structure and impurities. The rivet was inserted through a hole while red-hot (approximately 1100 degrees Centigrade) and hammered on the ends. Notice how the softness of the material allowed it to be deformed without major cracking and how the longitudinal filaments bent along the same lines of force:
Despite a repeated refining process, wrought iron still contains many impurities. I call them “impurities” not as a term of abuse for an inferior material, but rather in recognition of the ubiquity of high quality steels which frame our world in the modern era. The impurities in wrought iron help to define it as a material, and it was a practical and advanced material in its time. In an era when aluminum was worth near its weight in gold and carbon steel could only be produced using laborious and inconsistent carburization techniques, wrought iron was the cutting edge (So valuable was aluminum before the development of the Bayer process of electrolyzing bauxite ore that the builders of the Washington Monument in the District of Columbia proudly crowned it with an aluminum capstone of 100 ounces in 1884, then the heaviest sample of aluminum in the world). Indeed, when wrought iron was in use, it was conceived as more pure and reliable than other competing materials. The filaments of silicates, inclusions, and other slag throughout the material serve as one of its most distinctive characteristics in terms of its appearance and performance.

Because the wrought iron is drawn out using hammers and rollers, the impurities are also drawn into thin strands within the body of the material. The result is a material with a striated texture similar to wood grain. These striations, regions of weakness within the surrounding iron, are often the site of stress cracking and failure of the material under stress. See Figure 3 below:
The Wrought iron bar above was hammered cold under a power hammer until the iron disintegrated along the strands of slag. Compare to a sample of mild steel subjected to the same treatment in Figure 4:
This steel, harder and much more homogenous than wrought iron, flattened neatly without separating.
Furthermore, the filaments of inclusions in wrought iron become more visible as it corrodes. The exposed iron oxidizes and flakes away, and the slag becomes part of the outer surface. Slag, composed mostly of silicates, does not corrode, so it forms a weather and corrosion-resistant sheath covering the iron. The iron surface then becomes textured with the longitudinal ridges of slag filaments. This distinctive pattern is clearly visible in Figure 5 below: This pattern contributes to its desirability in some ornamental work today.

The inclusions in the material also allow for forge welding without flux. When bare iron or steel is heated, it hyperoxidizes in the atmosphere and quickly produces “scale” on the surface. This scale, essentially sheets of thick silvery rust, must be brushed off the surface continually, lest it be hammered back into the material and spoil its integrity. Scale, when introduced into the material, compromises its strength and aesthetic appearance. Moreover, if two pieces of iron or steel are heated enough to be welded together, any scale in the joint will prevent a tight bond. When welding steel, one must coat the surfaces to be welded with flux, a nonreactive coating such as Borax, which separates the hot steel from the atmosphere and is squeezed out when the pieces are hammered together. Wrought iron also produces some scale when heated, but it can often be forge welded without flux. As the wrought iron heats up, the slag melts and forms a coating on the surface of the iron. When white hot (aka at a “welding heat), the wrought iron “sweats,” that is, the impurities coat the surface and give it the appearance of dripping liquid. As two heated segments of wrought iron are hammered together, the iron sticks and squeezes out the slag just as in the shingling process mentioned in the puddling process above.

Because wrought iron is the result of the judgment and intuition of skilled puddlers rather than the exacting calculations of machines and computers, it is a highly variable material. From puddler to puddler, and even from batch to batch, the composition and precise properties of the iron can differ in the same way that a baker never bakes the same loaf of bread twice. One common result is an area within the material with more or less inclusions and slag than the body of the material. This region of concentrated impurities may be invisible at the time of production, but it can become visible as the iron ages and corrodes. The arrow in Figure 6 below points to a pit, over one centimeter deep, betraying either a zone of high slag (which fell out like a knot in a wooden board) or a zone of high purity (which rusted out). This iron dates from 1868.

This pitting also occurs on a smaller and somewhat more uniform scale on the surface of wrought iron as it weathers. Not only do the filaments become apparent, but regions of varying composition also reveal themselves as small pits across the surface of the iron in both the image above and the one below: The inclusions do more than determine the iron’s appearance. When heated in a forge, wrought iron has an earthy smell distinct from steel. When hammered cold, a wrought iron bar produces a “thud” sound rather than the ring of steel. One can distinguish wrought iron from steel using all senses but taste.

Wrought iron began to fall out of commercial use in the mid-19th century due to the introduction of the Bessemer Process, which produced quantities and qualities of carbon steel which far exceeded the production and quality of wrought iron. Gone were the days of the skilled iron puddler plying his craft, producing perhaps a ton of wrought iron on a good day. A single Bessemer furnace could produce 120 tons of carbon steel in one day using low-skilled labor. The social networks dependent upon wrought iron production also rapidly disappeared; the master/apprentice system gave way to increased automation. Skilled laborers were replaced by low-wage unskilled immigrant labor. As the technology became obsolete insofar as industry was concerned, so too did the people who depended upon it for their livelihood. Factory owners clashed with their employees as factories were retooled, culminating in the bloody Homestead Strike of 1892. One of the most defining moments in American labor history hinged upon the materiality and affordances of wrought iron.

Today, if the material is recognized at all it is treated by consumers as a novelty and by some metalworkers as both an aesthetically desirable and nostalgic commodity. Wrought iron maintains a feel and a look not easily duplicated in steel. For some traditional metalworkers, contact with wrought iron is a material link to the past. Despite never knowing who made a given sample of material, wrought iron carries for some a unique presence because it is the result of intense technique and attention rather than the output of an automaton. It is not so much a product as it is a residue of human agency, an artifact of a bygone era before the bifurcation of craft and industry.

No commercial iron puddling factories continue operation, and wrought iron from old fences, bridges, and water towers is recycled. Quality wrought iron can fetch over US $1 per pound (for comparison, copper has recently soared to US $3.70 per pound). Wrought iron maintains qualities desired in fine ironwork: softness, malleability, texture, ease of welding without electricity, attractive weathering patterns, and the certain nostalgic value of working with a material which the iron and steel industry has considered obsolete for over a century.

Materiality matters. The matter-reality of wrought iron was developed with certain scripts in mind, but it also continues to write scripts upon those who use it. The various affordances of the material determine how it is produced, how it looks, how it functions (or ceases to function), how it can be modified, and how it can be used (or re-used), and even how humans have organized themselves. Materiality is not a surface, but it can bear surfaces. It is not a symbol, but it can serve as symbols. It is not a script, but it can receive scripts and force its own in return. Materiality is not a product of society, but a prerequisite.

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