How to Repair a Glaze Bubble on a Ceramic Mug

Bubbles in ceramic glazes are frequently caused by either over application of the glaze, meaning the glaze is too thick; under firing the kiln, meaning it doesn't get hot enough before the firing is over so the glaze never melts properly; or firing the kiln too fast, meaning the kiln reaches its required temperature too soon and doesn't allow the glaze long enough to melt. Any of these can cause little bubbles, or "pin holes," to form in the glaze and if the glaze doesn't get to the proper temperature for a long enough time, it doesn't hit the correct melting point to allow these defects to smooth out. This is repairable, although nothing in ceramic firing is ever guaranteed.

Things You'll Need

• Grinding wheel
• Glaze
• Kiln

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Instructions

1. • 1

     Grind the area of the mug that has the bubble down lightly with a fine grit grinding wheel. Do not try to grind all the way down to the stoneware. Instead, grind away the bubble ridges, leaving a fairly smooth surface to re-glaze.

   • 2

     Reapply a light coat of the same glaze to the affected area of the mug.

   • 3

     Re-fire the piece. Make sure that when the kiln is fired, it is fired to the correct temperature for the glaze, and that it is allowed to run for the correct amount of time to get the best firing.