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Dealing with Trapped Air Bubbles

 

This is part three of a multi-part tip on ways to repair or eliminate trapped air bubbles.  Click here to go to part one.

An alternative method to eliminate or greatly reduce air bubbles involves re-firing the piece to a temperature that's high enough to allow trapped air bubbles to rise to the top of the piece and escape.  This approach can be used for both initial firings and for re-firing pieces with trapped air bubbles. 

 

To use this method, first fire your piece to around 1700F/925C.  At this temperature the viscosity of the glass will be low enough that bubbles will rise to the surface of the glass and escape.  You'll need to soak the piece for a while to give the bubbles time to pop, so watch carefully until the bubbles rise and pop.  Continue soaking until the glass smoothes out, then anneal and cool as normal.

 

Although this approach won't get rid of all of the trapped air, it will tend to leave only very small bubbles or slight "pin pricks" where the bubbles rose to the surface and popped.  Be aware that some glasses change color when fired to high temperatures.  There is also a tendency for devitrification; in addition, glasses that are repeatedly fired to high temperatures can become incompatible.

 

But the risks of firing to high temperatures are often outweighed by the results.  Firing to high temperatures almost never fails to surprise, and usually yields results that can't be duplicated with any other approach.

 

This technique, also known as high temperature firing, will be discussed in more detail in a later tip.

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Copyright 2006 Brad Walker.  All rights reserved.

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Copyright 2005-2006 by M. Bradley Walker.  All rights reserved.

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