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Making plaster casts of coins

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Rupert:
Here are my first results in plaster casting interesting coins for Curtis. Actually, this was the second attempt, since first time there were too many bubbles. Brushing the moulds with spirit did solve this problem but made the plaster adhere a lot more to the talcum-covered mould, so I had to destroy the moulds to get the casts out. All the rest worked very well, the casts on the left only look bad because the coin looks bad in the first place.

Rupert

dougsmit:
There is a commercial product to prevent bubbles in plaster casting called Airid.  I have not had any problem with sticking using it (but I have not made a cast for several years now so I really don't know if it has a shelf life).

curtislclay:
Casts sticking in the mold is a mystery to me: I've never had trouble removing the casts, whether or not I brushed in alcohol before pouring the plaster.

Bubble trouble should only occur with EF coins. Maybe the bubbles in your first batch resulted from too thick a mixture of plaster and water; use a little more water to make the mixture more fluid. And try to pour the mixture in slowly from one flat spot in the mold, so as not to entrap bubbles in the details.

I look forward to checking the obv. die on that unique Albinus As!

Sosius:
Mr. Clay,

I just wanted to thank you for this post.  My kids and I have spent many hours making plaster casts using your method.  Not only have we done coins, but we have made casts of jewelry, beads, rocks, hand tools, ceramic flowers, nuts and bolts, football laces, shoe soles, dog/cat feet (the cat didn't like it so much), and we even made nameplates for the kids' doors!  It has saved us on several rainy and/or cold days when we couldn't play outside. 

Thanks again,
Cliff

curtislclay:
Cliff,

I am glad that you and your kids have found cast-making to be to be such a useful and even fun activity!

To give credit where credit is due: Michael Metcalf, a curator at the Ashmolean Museum, taught me the basics of casting, as I was about to set off on my first museum tour, spring 1967. A couple of years later, somebody else, I can't remember who, told me about the trick of pouring off most of the excess water before stirring in order to produce the right creamy mixture. Finally, around 1980, Hans Markus von Kaenel taught me how to use denatured alcohol to eliminate bubbles. I couldn't believe that that trick had remained hidden to me for so many years: I had earlier asked at least a dozen numismatists and museum curators how to eliminate the bubbles from casts of sharp coins!

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