Saturday, April 2, 2011
How to size a bezel setting for COPPRclay.
A really important thing to keep in mind when making a bezel setting out of COPPRclay: shrinkage is 20%, but don't be fooled, that doesn't mean make your setting 20% bigger. So how do we determine the correct percentage? First get a tape measure and measure the perimeter then go to Metal Clay Shrinkage Calculator enter that figure into the final clay size field, select your clay (for this example COPPRclay) and it'll spit out your greenware measurement. Okay, now divide that number with the original measurement then move the decimal point over two spaces to the right and voila, you've got your percentage, which should be right around 125%. If you were to simply add 20% to, lets say, an 8mm measurement you'd actually come up with 9.6mm, because 20% of 8 is 1.6. So you need need to increase by 25% to reach the correct size of 10mm.
I know blah, blah, blah, give me the meat already. I first came across this technique in a Hadar Jacobson book, but done with silver clay: Okay, take your cabochon to the photocopy shop (yes those still do exist) and run off a copy that's set to 125% of the original size. Or if your printer is actually calibrated to print off the exact size of a scan, you can scan then increase the size in an editing program by 25%, just make sure to print off the original size on the same sheet to ensure it matches up with the actual cab. You should see the weird looks I get at the aforementioned copy shop, leering over a Xerox machine, clutching a bag of rocks, carefully laying out all my stones.... making photo copies... of rocks.... I've officially become "that" lady...
Now take your handy, dandy photocopy and cut out your cab, make sure you've got the correct side facing down, i.e. if you set the flat part of the cab on the machine's glass surface, you've copied the bottom, sooo place the copy image side down to the inside face of the base for your setting. That may not matter too much with symmetrical shapes, but it's good to remember just in case you set an unconventional stone. Also if you are planning to add a bezel wire to the inside of the setting you will need to change the sizing to accommodate, perhaps even photocopying with wire in place, or you can do it mathematically (riiight...)
You don't have to understand the math, I certainly don't, just take my remedial algebra (I think I used algebra?) at it's word, or number. As an aside, I've got to take a moment to vindicate my high school math teachers: Mr. Dale and Mr. Walker, you were both right, I do indeed need math to make art.
Anyhoo, so far so good, although the next time around I'll maybe try using a thinner bezel. This whole project was inspired by Lora Hart's Cornerstone Challenge on Flikr, great way to get inspired to maybe push a little further. And in this case, think more than I generally care to!
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