Cremains of the day
Nov. 27th, 2016 05:03 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
offcntrHad a fellow come into the booth yesterday with an... interesting request. He was in possession of his buddy's ashes. Cremation remains. Now if he'd wanted me to make him a container for the cremains, I'd have been totally ready. Said buddy was a hunter and fisherman, and the patterns I paint would've been perfect for the project. But he didn't want me to make an urn for the ashes.
He wanted me to make an urn with the ashes. Mix them into the clay, or the glaze, or both.
Uhm, no.
Quite apart from the ewww! factor, there are technical issues involved. Cremains are not ceramically neutral. They're mostly bone ash, with a bit of iron oxide and other trace minerals. Bone ash is a flux, a chemical that lowers the melting point of ceramic blends. Mixed into the clay body, it might lower the firing range by a couple of cones. It might change the thermal expansion of the fired clay, causing the glaze to craze, or worse, shiver. Unless it's milled very fine and sieved, it might cause lime pop-outs, little chips popped out of the clay when calcium carbonate is calcined to calcium oxide, then rehydrated to calcium hydroxide, expanding and blowing bits of clay out of the piece.
A better use might be in a glaze. Bone ash is a component of a lot of microcrystalline iron glazes: Kaki, Shaner red. With some testing, I could probably even coax a workable version of my beloved Best Possible White out of it, subbing ash for the talc and whiting.
But there's the rub. Testing. I'd need to mix up tests, fire them, adjust the recipes, fire again. With my fifty cubic-foot kiln and once-every-six-weeks firing schedule, this project could take all year.
More importantly, not all tests turn out. The failure rate is high, unsuccessful tries are thrown out. And I just don't feel comfortable treating the remains of a person like that. Like raw material.
He wanted me to make an urn with the ashes. Mix them into the clay, or the glaze, or both.
Uhm, no.
Quite apart from the ewww! factor, there are technical issues involved. Cremains are not ceramically neutral. They're mostly bone ash, with a bit of iron oxide and other trace minerals. Bone ash is a flux, a chemical that lowers the melting point of ceramic blends. Mixed into the clay body, it might lower the firing range by a couple of cones. It might change the thermal expansion of the fired clay, causing the glaze to craze, or worse, shiver. Unless it's milled very fine and sieved, it might cause lime pop-outs, little chips popped out of the clay when calcium carbonate is calcined to calcium oxide, then rehydrated to calcium hydroxide, expanding and blowing bits of clay out of the piece.
A better use might be in a glaze. Bone ash is a component of a lot of microcrystalline iron glazes: Kaki, Shaner red. With some testing, I could probably even coax a workable version of my beloved Best Possible White out of it, subbing ash for the talc and whiting.
But there's the rub. Testing. I'd need to mix up tests, fire them, adjust the recipes, fire again. With my fifty cubic-foot kiln and once-every-six-weeks firing schedule, this project could take all year.
More importantly, not all tests turn out. The failure rate is high, unsuccessful tries are thrown out. And I just don't feel comfortable treating the remains of a person like that. Like raw material.