Wire: Strip-Twisting Method

by Jamie Hall on September 1, 2010

In April, I did a post on wire-making tools, which briefly touched on different methods of wire production. There’s a proper discussion of some of the methods in Gold Bulletin: The Production of Gold Wire in Antiquity, by Andrew Oddy. This time, I’m looking at the strip-twisting method in detail.

Coatsworth and Pinder have described the three methods of making wire that were available to the Anglo-Saxons: strip-twisting, block-twisting and wire drawing…In the strip-twisting technique, a narrow strip is cut from the edge of a sheet of metal. This is then twisted until it forms a helical tube with an open centre. This tube is then rolled between two smooth blocks of stone or metal which compresses the tube which will, in the case of gold, cold weld to form a round-sectioned wire.

– Kevin Leahy, Anglo-Saxon Crafts, Chapter 9, p149


I’m using sterling silver strip in this experiment, rolled out from round wire. This is more regular than strip hammered from square wire or cut from a sheet, so the test will need to be repeated in the future using these methods (Leahy also mentions using gold – perhaps fine gold or silver would be the ideal materials to try next time). The thickness of the strip is very important. The first picture shows a failed attempt, using 0.9mm thick strip, which lacked structural integrity, and wouldn’t form a regular tube. The second picture shows the 0.2mm strip which I tried next – this was very effective, although there may be a “sweet spot” between the two sizes.

Strip-Twisted Wire Initial Stage

The strip was well annealed before use; it had to be, otherwise the strip unravels as soon as you finish winding it around the core. In an ideal world, another piece of wire would be used for the core – the strip is wound around the strip until it forms a tube; the core is removed by pulling it out. Even without another piece of metal wire, a rolled out length of beeswax will do, so this wire-making technique could be establised as soon as sheet could be cut into strips (no chicken-and-egg scenario here). I’ve tried both methods – a pre-made wire makes the best core, as it thin and regular, and the beeswax core had to be melted out, which was messy. The strip should be wrapped evenly around the core; any imperfection at this stage will be difficult to remove later.

Strip-Twisted Wire @ ~2mm

Once the basic form has been twisted around the core, there doesn’t seem to be any benefit is twisting it further – it just bunches up and deforms. Oddy recommends that it should be twisted by hand before rolling, but this seems pointless – hand twisting is a poor replacement for using blocks, which are used in the same way as the block-twisting method. Unlike block-twisting, wood is a suitable surface, presumably because strip-twisting isn’t mechanically compressing the wire – rather, it is lengthening the coil of strip, and the reduction in wire thickness is a side-effect of this, if you like. In my case, I used a piece of pine 2’x4′ and a wooden bench. I tried rolling in one direction, and rolling back and forth – it didn’t seem to make any difference to the result, and rolling it in both directions is a lot easier. The picture (right) shows the wire after the first rolling – at this stage, it’s about 2mm round.

Strip-Twisted Wire @ 1.5mm

In the initial stages, a very gentle touch is needed – too much pressure, and the tube will collapse. It is also important that the rolling surfaces completely cover the tube; if the ends of the tube stick out at any point, they will be unravel, and have to be cut off. I expected that the tube would continue to be very delicate, but once it was past 1.5mm, it became very hard to roll it by hand – with my spindly arms, I was unable to apply enough pressure to reduce the wire any further, even after annealing it again. Even leaning on the block with my upper body wouldn’t squash the wire at this point.

Strip-Twisted Wire @ 1.1mm

After some consideration, it occured to me that we don’t use our feet very much for modern production techniques – in the middle ages, one method of drawing wire was to stand on a drawplate, or to use a swing, and push against the drawplate with both feet. With this in mind, I found a smooth wooden block big enough to stand on, and put the wire on the floor, which is tiled with polished marble (it’s a long story – we don’t work in a palace, honest), and covered it with the wooden block. Carefully holding my bench, I rolled the block back and forth with my feet, placing as much of my weight as possible directly over the wire. I wish I had a photograph of this, because it looks extremely silly, but is a very effective method of applying force. Using this method, I was able to reduce the wire to 1.1mm round. I may have been able to take it further, but the wire lengthened so much that it became too long to be covered fully by the wooden block – from it’s initial 65mm length, the coil extended to 200mm. As I didn’t have another wooden block, I had to give up. Realistically, I don’t expect to have been able to go any further using just my weight.

In the linked article by Oddy, he suggests that the wire could be further reduced by pulling it through a drawplate, in a similar way to strip-drawn wire, meaning that soft metal, or even wood, drawplates could be used. I haven’t tried this; I’ll post an update when I do. This would certainly be a good way to get around the need for more weight. Failing this, applying more weight would require a team of people. The logical approach would be to use a large, heavy piece of stone mounted on a smooth metal or wooden board. Ropes could be used to pull the stone back and forth by two teams of people, and several lengths of wire could be rolled at the same time (rolled several wires would make it easier to keep the stone balanced. A simpler method might be to get a board big enough for two people to stand on, and hold onto handles above their heads while they move their feet back and forth.

Bent Strip-Twisted Wire 2

Without further processing, the “wire” at 1.1mm is really tube, and apart from straight lengths, it is quite unsuitable for use. The smaller the internal diamater of this tube, the better it’s mechanical properties would be. The picture (left) shows the wire after bending – it suits gentle curves more than right-angled bends, and it reacts better if bent around a regular form than if bent by hand. Even with a significant reduction in thickness, this pseudo-wire would be less effective than any of the other methods that I have covered. It would only really be useful if it was reduced enough that the internal diameter of the tube was reduced to less than the wall-thickness of the strip used to make it – in this case, 0.2mm – and that would be hard work. Using .999 fine metals might allow proper fusing into proper wire, but presumably the metal would have to be perfectly clean to do this. The other real limit with this method is the length of wire, which is dependent on the size of blocks that are available.

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