For this month, I thought I'd showcase the first finished piece from my Metalwork & Jewelry class at Montclair State University (MSU). It's a solid sterling silver pendant, created using a cuttlebone cast. I've used a gunmetal pinch bail and 2mm black leather, which I had left over from Artbeads.com's Use The Muse contest kit. I also used a silver-tone claw clasp.
Cuttlebone casting is not too difficult, although it did take me two tries to get this right. The first time, only the bottom of the piece came out...the top must've been the victim of an air bubble or something. :\
Cuttlebone is the internal shell of the Cuttlefish, and can be purchased at pet supply stores, since it is used as a supplement and exercise toy for birds. Apparently, it is high in calcium, according to About.com (http://birds.about.com/od/birdcages/f/cuttlebone.htm).
To make a cuttlebone cast — which can only be used once, BTW, since it is scorched during the process of pouring the molten metal of choice into the cast — you take a piece of cuttlebone and cut it in half for smaller pieces. If you are making a larger piece, you can use two separate pieces. There is a smooth side and a rough side. Rub the smooth sides together to make a flat working surface. Be sure both sides of the cast are close to the same size...otherwise, you run the risk of having the metal seep out. This happened to me both times...it leaked out the bottom of my cast, even though I did my best to take precautions. Once you have two similar-sized halves of your cast, carve a "funnel" in the top to make it easier for the metal to travel to your carving. If metal stays in this portion when making your piece, you can saw it off later. When carving your design into the cuttlebone, keep in mind the use of negative space. The metal can flow into any areas that are carved out, so if you want areas without metal, do not carve those out from the surface. If you want a three-dimensional piece, carve the mirror image out of the opposite side of the cast. Also, molten metal can only flow downward, so if your design has any parts that point upward, they won't receive metal. Be sure to keep at least 1/4" or so around the perimeter when creating your design, which will minimize leakage. Don't carve too deep if you're making jewelry because the piece will be thick, chunky and heavy. It's fine for sculptures, though. Also, there is a natural pattern in cuttlebone, which will appear in your piece. See all of the ridges and lines in the pendant? That's all natural texture provided by the cuttlebone.
Once you have your carving all set — cuttlebone is pretty soft, so you can use any tool to carve it...I used one of my needle files — tape the two pieces of cuttlebone together with masking tape. Be sure the two sides are lined up as you want them, since you only have one shot per cast. Put the cast in a third arm (a stand with a set of tweezers to hold the item in place), and use a high powered torch to melt your metal. Be sure you have enough metal to fill in your piece! Better to have too much than too little. Fine and sterling silver, brass, bronze, and gold can all be used. Copper can be used if it is mixed with 30% silver. Otherwise, it won't hold the shape of the cast.
Borax flux (sprinkles like salt) is added as you melt the metal. Sunglass goggles are recommended because of the power of the torch needed to liquefy the metal. Once the metal is fully melted, pour it quickly but carefully into the cast, as it will cool and take the shape of the carving pretty quickly. Try not to waste any metal, especially if you're using precious metals like silver or gold!
Once the metal has cooled — the metal at the top of the cast will change from a lava-looking orange color to dark — you can cut the tape holding the cast together and reveal your piece. Put the piece into a bowl of cool water using tweezers to cool the piece off, then you can pick it up out of the water. Before you douse it in water, it's too hot to touch. Put the piece in a pickle solution to clean off any oxidation. Cut off any extraneous pieces with a jeweler's saw, then file and sand the piece to make the edges smooth. If you wish, you can polish it with compounds on a wheel; we have bobbing, Tripoli and red rouge at school, so I used those (maybe I'll cover the various compounds in a future month). I drilled a hole in the top of the pendant for the bail, and voilà!
If you're interested, I found this step-by-step instruction with photos at Tumbleweed Glass Studio (http://www.tumbleweedglass.com/cuttlebone.html).