ASH - Used in pottery.
Ash is the powder left after the combustion of any material. The ashes used in pottery are natural, made from trees, plants and animal bones and these can be bought prepared as very fine powder. You can make charcoal powder by burning down boxes such as those used for packing fruit and vegetables. The ash must be broken down into a fine powder, sieved to take out all the rough bits. Cover it with water and pass it through a sieve with a fine mesh, repeat this several times, then lay it out on a flat surface to dry. When dry store it in an airtight jar.
In pottery charcoal powder is used to mark out the outlines of designs. The design should be on transparent paper and pounced, laid on top of what is being decorated and rubbed with a small bag full of ash, which goes through the holes and marks on the design. As charcoal powder is a natural product it will burn away when fired at 700º C. and for this reason, when pieces are fired at 980º C., the remainder of the product will then disappear.
As ashes form part of a glaze and are easily melted, their function is also to help to bring the firing temperature down and create transparent effects.