Small Pyrometric Cone 021 for Kiln-Sitter

This is Cone 021 in Orton's small regular SRB series, made for the Dawson Kiln-Sitter rather than the kiln shelf. Orton lists it bending at 643°C (1189°F) at 300°C an hour, the only rate published for this size, measured in a gas fired kiln. The cone is tapered, so where the sensing rod sits on it makes a difference. The thin end fires cooler and the thick end hotter, and the gap between them is about half a cone. Small cones also bend 7 to 10°C (12 to 18°F) earlier than a self supporting cone of the same number, so do not use a self supporting figure for one of these. Orton lists cones in this part of the range for overglaze decoration, lustres, enamels and decals, and for fusing, slumping and decorating glass. If a firing comes out short, Orton says to load the next cone hotter into the Kiln-Sitter and put a witness cone on the shelf to see what the kiln actually reached.