Topics: Art Clay®, Warping, Firing

Q.
I notice that after firing my Art Clay with a torch, it no longer lies flat (when it was flat before firing). Am I firing too long, or not long enough?
- Heather
A.
Warping or distortion often happens if the flame of a torch is concentrated for too long in one part of the piece or when a piece is too large to be fired with a torch. A piece that is heavier than 25 grams or is larger than a half-dollar, in thickness and diameter, should be fired in a kiln.

If your piece is smaller than a silver dollar and less than 25 grams, go through this check list before firing your next piece:
  • The object being fired must be completely dry
    • If you are unsure if the piece is dry, place it onto a mirrored surface; let it stand for a moment then remove. If there is a haze at all on the mirror, the piece is not dry. Wait overnight before proceeding.
  • Place the dried piece onto a fire block
    • Do not use ceramic since it can crack or splinter when used for heating metal clay due to the concentrated heat in one area
  • Trace an outline of the piece onto the fire block
    • The outline will help you gauge how much the piece shrinks when fired. If the finished size is not 8% (or more) smaller than the original size, it was not properly sintered (fired). Start over.
  • Dim the lights in the room, if possible
    • The dim environment will enable you to assess the color of the glow as the piece is heated
  • Set a timer for the appropriate amount of time:

    Clay Volume 5g 6g - 15g 16g - 25g
    Firing Time 1 - 1.5 min 1.5 - 2 min 2 - 2.5 min

  • Put on your safety glasses
  • Start heating the piece with the torch. Be sure to keep the torch moving in a circular motion so as not to heat one part of the piece longer than the rest. Once it reaches a peachy salmon color, start the timer. Heat until the time is up.
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