Difference between revisions of "Iron Working"
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Iron was a very important commodity to the Anglo-Saxons and Vikings, and those people who were lucky enough to be skilled in working it were held in high regard. The reason behind this is the versatility of iron. The Bronze Age had come and gone, and found many uses for bronze, but with the discovery of how to smelt and process iron, a whole new range of products could be made. Most farms would have had their own small forge where the farmer would be able to make or mend simple everyday items. As it was quite expensive the iron he used often came from reforged broken tools or other items. More complicated tasks would be sourced from travelling smiths who came to the farm, or forged by the village or town smith. The demand for iron products by royalty and noblemen meant that they had their own dedicated teams of smiths.
Iron was used to make diverse items from nails to swords, with a nail for example taking no more than one minute to make and a fine sword taking a week or so by a specialist weapon smith. A number of cooking utensils, pans and cauldrons were also made of iron, with the consequence that these things lasted much longer and couldn't be burnt. Flesh forks for boiled haunches of meat that looked like torture instruments, were forged out of billets of iron, whereas cauldrons were made out of sheets of iron, that were overlapped and riveted. The seams were beaten together so that they became watertight joints and didn't expand apart in the heat of the fire. There really wasn't a craftsman who didn't rely on the smith for many of his tools.
The most important of all of the tools made by the smith was probably the knife, which had an enormous number of uses, especially as people lived off the land far more than we do today. So whether the knife was just for eating, or was a specific tool just for carving wood, it still had to be made well. Although a knife appears simple, the cutting edge was made of steel with a softer iron back 'fire welded' to the blade. The reason for this was to economise on the amount of steel that was used, as it was a rarer product of iron making. We are not entirely sure, but we suspect that steel was a happy accident of good iron smelting, but didn't occur in large enough volumes. So it was carefully used in controlled amounts. Steel also keeps a better cutting edge than iron, but because of this property, it tends to be more brittle. Iron was then employed to make the bulk of the tool as it is more forgiving. Not far away from the forge would have been a rotary grind stone. With this and copious amounts of water, the edges of blades on all sorts of tools or weapons were honed to sharpness. Little grind stones roughly only five inches in diameter could be mounted on pole lathes to turn them, but larger stones would have had a man or men to turn it rapidly.
Fire Welding was the only method other than riveting to join two pieces of iron together permanently. The art lay in judging the temperature of the two elements in the forge. Often the two pieces were wired together to anchor them in place temporarily. When the iron and steel were on the brink of burning in the forge, just as white sparks begin to fly from the work, the billets were whisked out of the forge and placed on the anvil. This is certainly a two man job, because one is controlling the tongs with the billets in, and places it on the anvil, whilst the other hits it smartly before the work has a chance to cool at all. Just one strike is enough to join the two pieces, scattering a shower of white hot sparks over the forge. Now you know why they wear leather aprons. Any reduction in the temperature would result in only a partial or poor weld. The work was placed back into the forge once again, without any delay. Some fine washed silver sand is flung into the joint to act as a flux, to reduce excess oxygen, and then the work is hauled out again in a another shower of white sparks. Now the real weld is made. The heavy hammer drives the two billets together joining them forever. From here on in, the work is to bend and reshape the iron and steel to your desired shape. Axes are made by folding iron around a socket, pinching the ends together with steel inserted at the business end during welding, to become the cutting edge. Other smiths were more talented in making locks and padlocks that had fine springs of steel in them to operate the locking mechanism. Even horses then needed and had shoes. They were cruder and heavier, and were made probably a little quicker with the nail holes merely punched out from the edge of the shoe giving it a wobbly outer rim.
In order to make anything the smith first had to obtain his iron. Again, he was unlikely to have smelted it out for himself. This above all was a messy and time consuming task that would have been done nearer the source of iron and away from the town. First he had to obtain the iron ore. This was generally obtained from deposits near the surface of bogs, and is called not surprisingly bog ore. This source of ore is quite iron poor, unlike the ores that were later to be quarried out from cliff faces. The ore is heated or roasted in a pit. This helps to break it down, clean it and dry it out. It's then placed on a larger stone and broken up into small nuggets. The iron ore was then heated in a chimney shaped clay furnace about four feet high and 16 inches across (a process called smelting) at very high temperatures to remove the impurities, known as slag. The smelter is made from clay with lots of 'grog' or straw mixed in to help it withstand the extreme temperatures. To do this the iron ore was layered with charcoal. The charcoal was then lit and the furnace had its temperature raised by using bellows. Sometimes to 1500℃ in certain areas of the smelter. Not too much air was required from the bellows as it could easily convert the ore just to slag by oxidising the ore rather than reducing it, so the process was a tricky one.
The iron then melted out of the ore and the slag collected in the shallow pit at the base of the furnace. The bottom corner of the smelter was broken open, the slag tapped off, leaving the smith with a fairly pure lump of iron called a bloom. Once the iron had cooled and set, a file was drawn over the surface to gauge the hardness of the iron bloom to see if it had any steel in it - the file being of a known quality itself. The bloom then had to be reheated and beaten over several workings to remove any other remaining impurities. The more diligently done the better, which resulted in nearly pure iron ready to be worked into many different objects. This type of iron is called wrought iron, but the Saxons were also able to add carbon (from charcoal) to convert it to steel. This was necessary where extra hardness and strength were needed, such as on knife edges, hammer heads or chisels. Another method was to roast the object in carbon dust in a metal box to create case hardened steel. The carbon penetrates the iron to a shallow depth converting it to the alloy.
Recent finds and work on the site at Hamwic (modern Southampton) have given us some new insights into Anglo-Saxon iron work. The quality of the iron has been shown to be superlative. So good in some cases that it's quality was not matched until the mid 1800s. The reason for this seems to lie in the work that was done to the iron to convert it to steel post the smelt. By a simple(!!) process of reheating the pure iron until it absorbed the relevant carbon levels to convert it to steel, until you could no longer heat it to good effect.
A sword blade required iron blooms to be forged into bars and strips of different shapes and sizes ready for use. Sometimes, especially for sword blades, the smith would twist together and fold bars of iron and steel to make the blade. This was a difficult and long winded process, but it meant the finished blade would be far stronger as it had the strength and hardness of the steel on the edges with the flexibility of the iron in the core. The twisting and folding of the bars of different metals gave a 'marbled' pattern to the surface of the blade which is called 'pattern welding'
The smith's forge had a fire in a hearth fuelled by charcoal, which was either a pit in the ground or, more usually, raised off the ground at waist height in a shallow clay bowl. Next to the hearth would be an anvil. The metal is heated in the hearth which is made hotter by blowing it with pairs of bellows, getting more oxygen from the air into it and raising the temperature to 900 - 1000°C. Glowing metal was held with a pair of tongs, and hammered into the desired shape on the anvil. The iron would stay hot enough to work for a minute or two only, less if there was a breeze to cool the work. He would also have punches with which to make holes, shears for cutting sheet metal and files for smoothing the metal. Next to his anvil he would have a supply of water and vegetable oil for cooling his tools or the items he was making. The forge itself is a dingy place, as it much easier to see the glowing metal in the shade. Also, when iron is heated to specific temperatures, it goes through several colour phases, known as straw to blue, each one indicating that the metal was either hot enough for a spring, or hard enough for a chisel.
Apart from smithying, he would have known how to solder brass and bronze together, braze it as well for stronger joints and how to tin plate objects. Depending upon the decorative nature of his work, he may also have known how to gild metals with an amalgam of mercury and gold. This last task was and still is very dangerous, because to get the gold to adhere to the iron or bronze, it is heated to vaporise the mercury, binding the gold to the bronze. The mercury oxide if it got into to your bloodstream via the lungs would affect your nervous system for good. Eventually killing you.
The smith would have been almost constantly filthy with charcoal dust etc. from the work, which makes me wonder as to how often he washed?
Original article by Roland Williamson November 1999; Illustrations by Colin Levick