{"id":984,"date":"2010-08-11T11:22:13","date_gmt":"2010-08-11T11:22:13","guid":{"rendered":"http:\/\/primitive.userblogs.ganoksin.coms\/?p=984"},"modified":"2011-10-15T22:35:58","modified_gmt":"2011-10-15T22:35:58","slug":"raising-an-anticlastic-bangle","status":"publish","type":"post","link":"http:\/\/userblogs.ganoksin.com\/primitive\/2010\/08\/11\/raising-an-anticlastic-bangle\/","title":{"rendered":"Raising an Anticlastic Bangle"},"content":{"rendered":"

$\"Anticlastic$ <\/a><\/p>\n

We received a commission from a customer for an anticlastic bangle. It’s not something I’ve made before. Fortunately, we do have an appropriate rounded mallet, made from lignum vitae, but I had to make some wooden stakes to form the bangle on. Raising is an important skill for the medieval period, and most bowls and cups would be made this way – spinning may have been practiced before the introduction of steam power, and later, the electric motor, but it’s use would be limited. Due to cost and time, I won’t be making this bangle as it would have been made in the middle ages, but the fundamentals are the same. The finished bangle is pictured left, and the process of making it is described below.<\/p>\n

$\"Silver$ <\/a><\/p>\n

Many of the readers on Ganoksin will be far better aquainted with raising than I am, but for those that don’t know, the terms “anticlastic” and “synclastic” refer to the direction of the curved axes of an object. An example of a synclastic object would be a bowl, whereas the bangle in this article is anticlastic, having a sort of saddle shape. For an illustrated description of these terms, and proper tools and technique for anticlastic raising, check out this excerpt from Tim McCreight’s book Complete Metalsmith<\/i><\/a><\/p>\n

$\"Hemlock$ <\/a><\/p>\n

Pictured above right is the sterling silver sheet that was purchased for the job. It still has it’s plastic cover on – I kept this on for the first round of hammering, but it had to be removed after that for annealling. I started by rounding of the edges of the sheet, to make the bangle attractive and easier to get on and off. Due to my circumstances, I wasn’t able to use the method provided by Tim McCreight, which involves bending the sheet into a flat bangle, and then using a sinusoidal stake to give it the saddle shape by curving the short axis. Instead, I was using a hemlock saddle stake (above) which I had made that morning from an old bannister. $\"Anticlastic$ <\/a> Due to it’s shape, it wasn’t possible to raise the bangle in the right order. Instead, I had to curve the short axis by laying the flat sheet on the saddle stake and beating it with the mallet. I then removed the plastic cover and annealled the silver. At this point, I decided to polish the inside surface of the bangle (pictured right), as it would be harder to get at later. As I was rough-polishing the silver, I just used a steel-cutting composition called Carbrax (which I highly recommend for silver and platinum). Bear in mind that this article is about a job in the modern workshop, not a medieval one, so the item will be polished to a lustre with a jeweller’s lathe and then tumbled in steel shot for a bright finish.<\/p>\n

$\"Anticlastic$ <\/a><\/p>\n

The second stage was bending the curved sheet into a bangle. To do this, I used the saddle stake again, but changed the way the mallet was used. Instead of beating the metal in the middle of the stake, I used the edge, which has a slight anticlastic form itself. This caused the silver to bend. Some work was needed at this stage to stop the edges from deforming too much, (which meant returning to the first stage occasionally), $\"Hemlock$ <\/a> and it did take a couple of passes before the bangle was bent into a semi-circle. The bangle after the first pass is pictured left. Due to the type of stake I was using, I had to change to a wooden bangle mandrel at this point, to turn the semi-circle into a proper circular form. Again, the edges deformed slightly, but this time I was unable to use the saddle stake to smooth them out. Instead, I made another stake, this time a “squared-off” dome (right).<\/p>\n

$\"Final$ <\/a><\/p>\n

With the dome stake, I was able to gently adjust the edges of the bangle, using the curve of the dome as a guide. Before this, I had been extremely worried about my ability to give the edges a smooth, regular form, but the dome stake was a better solution than I could have hoped for. After that, it was just a matter of making sure the bangle was properly pickled, polished with carbrax and tripoli, and then barrelled. At the time of writing, the piece is still in the barrel, so the image of the finished bangle (top) isn’t at it’s best.<\/p>\n

<\/br><\/p>\n

There are several improvements that could be made to the process. First, I would clean up the stakes – they were roughly filed, which left some impressions on the wood. Second, I would reduce the hardness of the mallet and the stakes, with the hope of getting a smoother surface at the end – I’m happy with the bangle, but very agressive abrasion and polishing would be needed to give it mirror finish, which may be what the customer is after. One possibility for the mallet is to use nylon or rawhide, and the stake could be covered with leather. Another option is lead – not a commonly used material now, but very important in the middle ages. A skin of lead could be formed over the stake, and nailed into place, and then a layer placed on top of the silver, to protect it from the mallet; lignum vitae is one of the hardest woods available. In an ideal world, I’d use a sinusoidal stake in metal or wood. The problem with that solution would be mounting it – I’d need to create a special vice to secure the stake. Does anyone know how horizontal stakes are mounted? it’s not something that I’d worried about before now, but I think it could be quite important.<\/p>\n

$\"leather$ <\/a><\/p>\n

UPDATE: I’ve made a second bangle, which is being hallmarked ATM, so I haven’t got a picture of it. I modified the saddle stake, by gluing and nailing some pigskin on it (right), and then used a sheet of leather between the silver and the mallet. This prevented the dimpled surface of the first bangle (top image), and only a small amount of abrasion was needed to give the bangle a smooth surface, which I’ll hopefully polish to a mirror finish when it comes back from the assay office.<\/p>\n

$\"Planished$ <\/a><\/p>\n

UPDATE: I’ve had a third chance to make one of these bangles – this time in fine silver, which was easier than sterling in some ways, but more effort in others. The planished effect took quite a long time to get right, and I maybe should have done the planishing before curving the bangle (although that might have had it’s own problems, as indentations might be “smudged” in fine silver).<\/p>\n","protected":false},"excerpt":{"rendered":"

We received a commission from a customer for an anticlastic bangle. It’s not something I’ve made before. Fortunately, we do have an appropriate rounded mallet, made from lignum vitae, but I had to make some wooden stakes to form the bangle on. Raising is an important skill for the medieval period, and most bowls and […]<\/p>\n","protected":false},"author":142,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[7],"tags":[],"_links":{"self":[{"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/posts\/984"}],"collection":[{"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/users\/142"}],"replies":[{"embeddable":true,"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/comments?post=984"}],"version-history":[{"count":4,"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/posts\/984\/revisions"}],"predecessor-version":[{"id":1062,"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/posts\/984\/revisions\/1062"}],"wp:attachment":[{"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/media?parent=984"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/categories?post=984"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/userblogs.ganoksin.com\/primitive\/wp-json\/wp\/v2\/tags?post=984"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}