Friday, 10 July 2015

Top ten tips on pottery firing

Pottery making provides some challenges for the beginner but non more so than at the firing stage. No-one wants to lose their precious ware after making it so lovingly. It is quite usual for small studio and craft potters to use intermittent box type kilns to fire their ware. Whether you use gas or electric as the energy source the principle is the same; heating an enclosed space containing shelves of pottery. Whilst the science of firing is quite complex and often outside the knowledge of many hobby potters most know it is important to follow some basic rules. The following tips are aimed at giving you the best performance from your kiln whatever the type.

1. Temperature uniformity is key to achieving consistent results. This should be the aim when firing your kiln.
2. Measure the performance of your kiln using bullers rings or Orton cones. Control it using an electronic temperature controller.
3. Record firing cycles used and settings for each firing as well as Bullers Ring or Orton Cone values.
4. Measure and record the gas or electricity used in KWH for each firing. The trends in this often give you a pre-warning of catastrophic failure.
5. Regularly calibrate thermocouples as they deteriorate over time.
6. Inspect refractory brick or lining regularly to ensure large cracks are not present. Remember large cracks in brickwork will affect kiln temperature uniformity.
7. Inspect electric elements regularly as over time they become brittle and may distort or break.
8. For gas users the colour of the flame is a guide to the kiln atmosphere. Yellow flame is reducing while blue flame is oxidising.
9. Placing ware affects the firing performance of the kiln. Large or thick walled pieces require more heat and act as a heat sink.
10. Don't be greedy- firing pottery too fast can lead to all manner of faults. Unless the glaze and body are designed to be fast fired don't do it!

More information and other technical articles on pottery and ceramics can be found at my website The Potters Friend.

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