FIRING (5) Decorated bisque in pottery.
Firing – decorated bisque: When clay has been fired it becomes bisque and can then be decorated and fired again. The heating up period can be quicker than with clay. With decorated work you must make sure that the pieces do not touch each other or any part of the kiln or its furniture and that they are completely clean on the parts they stand on. Slips and glazes work as glue and will adhere to anything they are touching when being fired. If you are firing a piece and are afraid the colors might run, stand it on a tile and bits, to protect your kiln. This will allow you to hold the pieces, so they can be separated by forcibly twisting them in opposite directions.
There are many types of colors that have different reactions and that may be fired at different temperatures. Work can be decorated and fired; more decoration can be added then fired again at the same or lower temperature. If colors that vitrify at different heats are going to be used, start with the ones to be fired at the highest temperature, re-firing at the same or lower temperature, never higher, otherwise colors could burn out completely. Always test colors that are fired above 1000ºC because if they have to be fired more than once, they can change and become matte.
These are different ways of decorating bisque:
ONGLAZE – 3 firings. Bisque. Glaze-base and finally the fired glaze is decorated with colors and fired between 700º and 850º C. Read more about: On-Glaze
GLAZE COLORS – 2 firings. Bisque and then colors and glaze are mixed and fired together. Read more about: Dry Cord 1 / Red – using it
INGLAZE – 2 firings. Bisque, then the glaze-base and decorating are fired together.
Read more about: Majolica: 3 – Decorating
UNDERGLAZE – 2 firings. The clay is fired and then decorated with colors which are covered with a transparent glaze; both are then fired together.
Read more about: Decoration – Dragons