Cuttlebone casting is an ancient, but very accurate method for one of a kind casting in precious metals or whatever. Cuttlebone is the backbone (sorta) from a cuttlefish. You can find it mail-order,but an easier source would be a pet supply. Bird lovers buy it for their parrots, keets, etc. to gnaw on. I'm not a jeweler, so this is something that I have done from time to time for gifts for wife, daughter, etc. The gold that I have used was saved scrap--broken rings/earrings 18k from Thailand, 10k HS class rings from when they were made in low grade gold etc. The little nugget that you will see in the photos was made from old 14k simple rings that my daughter had. Yes, I know that you may wish to do it lost wax, but this is a fast method and easily as accurate as lost wax without the time and expense. Fun and quick!
Free advice: The first time that I did this, I melted all the scrap gold that I had saved over the years--20+ years ago. I made a beautiful nugget of about 1 1/4 oz and gave it to my frau for Xmas. She loved it until she wore it for the first time. It was so heavy that she bruised--not happy---HA!. Since that first attempt, I've cast other things, i.e. a necklace drop wherein I used a small cone shell that I collected while living in Hawaii--that worked great--keep it small! If you want to do a small nugget, use a small rock as a pattern. I suggest that you use water displacement as a guide for the weight and volume that you need.
Picture #1 shows a piece of cuttlebone and a piece with the pattern. As you can see from the pic. you cut the cuttlebone in half, sand the soft surface to flat. Press the pattern half way into one piece of bone.
Picture 2 Now press the other half of the bone over the pattern. While aligned cut notches into the bone halves. Remove the pattern, cut Sprue and gating, blow out the loose calcium, and using soft wire, realign the two halves of the pattern. You are now ready to pour.
Picture 3 This shows the finished product after a bit of polishing. I used a bud torch for the melt and melted in a small steel ladle that I normally use for lead. I heated the ladle to red heat, shook off residual lead and melted the gold with the torch. Be sure to get it very fluid! A gold flux would have helped, but as I said, I'm not a jeweler and this works. If you do a great job on temperature of the pour, you will get very fine lines on the casting from the cuttlefish bone. Don't try, my opinion, to polish the lines out--this just adds interest to the piece and makes it unique.
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