Monday, October 13, 2008

Touchstone Silver

History, Purity, Clarity, Simplicity

A naturally occurring mineral helped create civilization as we now know it.

There is so much in the news right now about the monetary system, commerce, banking and the economy. But stepping back to the time when barter was the method of exchange of goods, before coinage and metal coins with specific value were used, there was a change that altered the ancient world.

Coins were minted by governments from precious metal, with the weight and value of the metal insured by the emblem stamped or minted onto the coin.

Coins could be made using an alloy instead of the pure precious metal, and the test for purity involved smelting the metal to separate the metals. Not a convenient way to establish value. Without it, though, the purity and value of a coin or bullion block was suspect.

But the discovery that a touchstone could easily determine if a coin or bullion block of metal was pure, by testing the metal to estimate the amount of pure gold or silver, led to security that the metal was worth its face value. And from there to the use of metal coins with a determined value for commerce, instead of the use of bartering for exchange.

A touchstone is a hard black stone, often jasper, hornblende or dark basalt, that the metal could be rubbed against to create a streak of color. When the streak from the unknown metal is compared with a streak left on the stone by one with a standard alloy or pure metal, the value could be easily confirmed. By treating the rubbing with aqua regina, a type of acid, the impurities would be dissolved out and the quantities of pure silver and gold could be verified.

Sterling silver is called the queen of metals, it is an alloy, a combination of silver with copper. A new sterling silver alloy, developed in 1990 by Peter Johns at the School of Art and Design in Middlesex University, is argentium silver, using some germanium in the alloy instead of part of the copper, to reduce the tendency of sterling to tarnish caused by oxidization of the copper in the alloy.

Sterling silver is guaranteed to be at least 92.5 percent pure silver. An alloy is used to strengthen the silver because pure silver is a soft metal and the addition of 7.5% copper makes it sturdier. Sterling silver doesn't have nickel in it, so it's useful for people who have allergies to nickel as it won't trigger an allergic reaction.

The word 'sterling' to refer to the silver alloy comes from England in the 13th century from the 'pound sterling' used as currency in England from the 12th century. Britainnia silver is an alloy of silver containing 95.84% silver introduced in England to replace sterling silver in 1697 as part of the recoinage to limit the clipping and melting of sterling silver and keep the coin of the realm out of the melting pot.

Silver is the most reflective metal, even more shiny than gold, and its white color is flattering to wear against the skin. For more history on silver and sterling there's an article on Wikipedia.

The photos are of pure silver charms I made and fired yesterday, from precious metal silver clay. Silver clay is not an alloy, it's pure silver, combined with an organic binder that allows it to be shaped by hand like a clay, but forms a pure 100% silver from firing to 1650 degrees F in the kiln to burn off the binder leaving only the pure silver. The earwires and headpins are handmade from sterling silver wire, to complement the look of the silver charms.

Because they shrink slightly as the binder burns off, any detail of the design in the clay is preserved in fantastic detail, and becomes smaller in scale without losing any of its visual and textural visibility and interest.

I tumbled these pieces to harden them and make them more reflective, since they are almost pure white when they first come out of the kiln. I have only slightly patinaed these to help the designs show up in the brilliant silvery reflections. Some others I made I will more deeply patinaed later today.

These will be great to use as charms, or on sterling silver earwires for earring drops. The patterns in the silver are vintage scroll and victorian script designs. Even though they are tiny charms, the detail from the silver metal clay is amazing. And they are not an alloy, they are pure silver or .999 percent rather than .925 of sterling.

There are pendants, disks, pairs of drops, charms and a toggle, all made from the empress of metals - pure silver.


Gaea said...

These are FAB! I love the coins!

LLYYNN said...

Gaea, I wanted them to look like they were salvaged from a shipwreck somewhere off the coast, like spanish dubloons or something. Thanks, so happy you like them. And the history of metals and civilization facinates me, we take so much for granted. Metal was a precious commodity at one time, rare and special and worked by hand.

Amanda said...

These look so great! The hearts are just awesome. (:

I'm a real fan of silver (I've never liked gold much up until recently, when I started using it with green stones), and it's been nice to finally learn more about it! I read somewhere that sterling silver was reliable for people with nickle allergies, but afterward I couldn't find that information again anywhere! It was pretty frustrating. I also had no idea that copper was a part of sterling!

Have you ever worked with argentium? If so, what are your thoughts on how it handles compared to sterling?

LLYYNN said...

If I use the argentium I would use it for fusing, and I haven't tried it yet. Since the PMC is pure silver and I use fine silver wire with it, I've been sticking with the sterling or pure silver to keep things simpler. If ya'll have tried some be sure to let me know how you liked it.

I want to put more silver in the kiln today, it's such a fussy process getting it ready and you have to work SUPER fast to keep it from drying out too much.