CONE (4) Witness.
ca: CON (4) Cocció.
Witness Cones are put inside the kiln, in different places, to check that the temperature is the same throughout it. After firing, it can be seen to what extent they have collapsed so that one can judge the heating of the different parts. Large cones should be used and the thicker end should be stood in a clay socket at a slant of about 10º from vertical. Place them in different parts of the kiln. If one has collapsed more than the others you will realize that part of the kiln is slightly hotter, or on the contrary, if one is straighter it will mean it is cooler. This can be checked when you open the kiln.
CONE, WITNESS. a) Over fired, b) Correctly fired, c) Under fired, d) Clay socket.