Casting Pewter
We've entered the Age of Metals!
Back in September, we did our first backyard pewter casting, using the lost-wax process with plaster molds. It took us while to source the metal ingredients to mix up the pewter ourselves, but finally we found them and then followed this recipe, by weight:
Jorge and I mixed up the metals in a big pot. You first melt the one with the highest melting point, and then the others in descending order.
We also heated up our plaster molds to about 235° C, in the kitchen oven, so the metal would flow better and to reduce any possible thermal shock.
All the pieces came out great, except for one of the Venuses, which has these curious bubbles or nodules on it, e.g. behind the underarms here:
If they had been air pockets in the metal, then you'd get pits or cavities. But nodules mean that it was the mould that had a tiny hole in it.
Our friend and neighbour Alexander, who is a sculptor and who has been joining us from time to time, said it could have been caused by tiny faults in the mould. When the hot metal enters, those tiny cracks open up and create a small pocket, which then creates the metal nodule. He suggested one way to safeguard against that would be to coat the object with a thin coat of plaster before covering it completely, so you might be able to notice any little air bubbles before hand.
Sigrid and Jorge have been doing some finishing work on their salamanders, and I did some on my yoni lingam piece, but I've been a bit stymied by how to fix up the bubbly Venus. Have to get some smaller files and Dremel bits.
In short, we're all ready to try another round, and I think we're all well and truly enthralled by Metal. Like so many things having to do with this Craft, it is hypnotizing. It draws you in to look at it, to stare at it, to stare into it, like a magic mirror.
Back in September, we did our first backyard pewter casting, using the lost-wax process with plaster molds. It took us while to source the metal ingredients to mix up the pewter ourselves, but finally we found them and then followed this recipe, by weight:
70% tin (melting point 232° C)
20% zinc (melting point 420° C)
10% lead (melting point 328° C)
Jorge and I mixed up the metals in a big pot. You first melt the one with the highest melting point, and then the others in descending order.
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| 1 lb of zinc |
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| 1/2 pound of lead shot |
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| after adding the tin and mixing, the oxidation produced these amazing colours |
We also heated up our plaster molds to about 235° C, in the kitchen oven, so the metal would flow better and to reduce any possible thermal shock.
And then we poured:
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Next, after a number of hours of cool-down, comes that truly magical moment of breaking the mould and discovering what has filled the void.
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| this mould broke very evenly, producing a great negative image |
All the pieces came out great, except for one of the Venuses, which has these curious bubbles or nodules on it, e.g. behind the underarms here:
If they had been air pockets in the metal, then you'd get pits or cavities. But nodules mean that it was the mould that had a tiny hole in it.
Our friend and neighbour Alexander, who is a sculptor and who has been joining us from time to time, said it could have been caused by tiny faults in the mould. When the hot metal enters, those tiny cracks open up and create a small pocket, which then creates the metal nodule. He suggested one way to safeguard against that would be to coat the object with a thin coat of plaster before covering it completely, so you might be able to notice any little air bubbles before hand.
In short, we're all ready to try another round, and I think we're all well and truly enthralled by Metal. Like so many things having to do with this Craft, it is hypnotizing. It draws you in to look at it, to stare at it, to stare into it, like a magic mirror.
And how delightful to find the same thing echoed in the words of Vannoccio Biringuccio, whose classic De la Pirotechnia (On Metals and Metallurgy) was written way back in 1540. In the chapter, "Concerning the Art of Casting in General and Particular," he writes:
"In order to describe the whole art in every part, I say that the greatest labors of both mind and body are required for its operations in the beginning, middle and end. It is indeed true that these labors are endured with pleasure because they are associated with a certain expectation of novelty, produced by the greatness of the art and awaited with desire, particularly since the artificer sees that it is an art pleasing and delightful even to ignorant men. As a result, as if ensnared, he is often unable to leave the place of work."(!)
And we're only just starting, we're only at 400 degrees...
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