Sunday, 23 March 2008

The saga of the silver

I was going to reply to Sparx's comment, but then decided there was probably enough of a tale here to justify a new post, so here goes.

It all started over 20 years ago. Jenny had not long finished her PhD, studying a Carboniferous fossil beastie which was largely aquatic, with short legs and a flattened, newt-like tail, though it was rather bigger, at about 3m long. For her birthday I wanted to find a way to give her a pair of earrings in the form of her fossil, so spoke to several jewellers in Cambridge. One said "If you carve the shape you want from this piece of wax, I can get it cast in silver for you." So that's what I did. I couldn't carve it small enough for earrings, so I made a bigger one, maybe 4 or 5 cm long, which eventually became a pendant.

The next few pieces I formed using plasticine on a piece of glass, Jenny poured silicone rubber over that to form a mould used to make the wax original, which we gave to the man. He encouraged us to buy a few tools and start doing some of the finishing ourselves, and so we came by some tiny files, a jeweller's saw, a few pairs of specialised pliers, jeweller's snips and finally a bench grinder, on which I replaced one of the grindstones with a polishing mop. Oh yes, and a simple gas blow-torch for soldering.

Somewhere down the line Jenny discovered a couple near Chelmsford who ran residential weekend courses, and we started going twice a year, which was always brilliant. And exhausting! We've done a little at home inbetween ever since, but silver is too expensive to keep much here. I tend to buy as little as we need for whatever we're doing, and fortunately the dealer in London, Blundell's (no website as far as I can tell) has no minimum order.

The blowtorch (basically just a nozzle attached to a handle, to which you screwed a 1 litre replaceable cannister of gas) was pretty cumbersome to use for soldering, so I bought a bottle of propane (red cylinder about 50cm high you might see at a camping and caravaning store - blue is butane which I don't think is hot enough), some orange rubber gas pipe and a couple of torches, with 3 sizes of exchangeable nozzle. I seem to recall I just paid a deposit on the bottle and paid for the gas, but I'm still using that first supply of gas. There can't be too much left in the cylinder now! The bottle has to live outside, in case there's a leak. Propane is heavier than air and would puddle in the cellar where we work, so would be incredibly dangerous.

Most items are made by cutting up bits of sheet and wire and soldering them together, smoothing down and then polishing up bright. This highlights an entertaining little facet of silver. The solder comes in several grades, which melt at increasingly high temperatures - 680° C, 730° C, 770° C (which is why you have to use a torch - an ordinary electrical soldering iron does not get nearly hot enough.) Sterling silver itself melts at about 890° C, which is worryingly close when you're soldering.

Unlike iron, which goes soft gradually as you near its melting point, silver goes from solid to liquid over a very narrow temperature range, and it's common for students to melt their work accidentally. Not usually the whole thing, just some critical part. The only answer is to chuck it in the scrap bin and start again. Even now, after 20 years, I still melt pieces occasionally. You see the solder go shiny and flow, and you wonder if it's gone all the way through the joint, so you heat it a little more just to be sure, and then the whole thing collapses! And the air turns blue!

At one point we tried to turn it into a small business, making jewellery in the form of fossils, but we quickly found it stopped being fun when we did that, so we stopped. In order to sell our jewellery, we had to have it hallmarked, so while we still thought it might be a goer, I registered my maker's mark and had a punch made up by the Goldsmiths' Company in London. If I ever want stuff hallmarked, I post it off to them, but mostly we don't bother. If you're not going to sell it, what's the point?

This hallmark has the maker's mark (not mine as I have no photo) LAO, a lion rampant, indicating sterling silver, 925 also showing sterling silver (parts per thousand), a leopard's head which is the London Assay Office mark, and the letter C which indicates the year. The year mark changes through the alphabet each year, changing case and having a different background shape, so with the right reference book, you can find when and where anything was hallmarked.
This picture shows some silver in the ladle, not quite ready to pour, since it still has lumps in. The lilac colour is misleading. In real life the ladle bowl is glowing a dull read, so I don't know why it's gone purple in the photo. I'm not good enough at image manipulation to fix it.

2 comments:

DJ Kirkby said...

I think this is the most beautiful photo ever, I am completly mesmersied by it and don't care that it doesn't look like that in real life...wow.

Rob Clack said...

Coo, thank you, DJ! Glad you like it. R