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    I was recently fusing coasters with some stringers in them.  I first fired the bottom sheet with the stringers on them.  I then fired them with a sheet of clear glass on them.  Bubbles appeared in the middle as well as on the edges.  What would happen if I drilled holes in the bubbles and then re-fired them?  Would it release the air and then lay flat?

    Thanks for your help.


    Stephen Richard

    Drilled out bubbles almost always show in the final product.  This is because the bubble has pushed glass to the side of the bubble, making the glass thicker there and thiner under the bubble.  You can fill the bubble with frit, but usually, it is still evident.

    I ahve no idea at what temperature you fired the bottom blank, but if you went to fire polish temperature, it is likely the edges of the coaster had begun to draw in, making the edges higher than the rest of the piece.  Two ways I know of avoiding this.  One is to cut the bottom piece larger than required, and then cut it to size when ready to cap with another piece – avoids the thicker edges.  Second is to put small pieces of frit at the corners of the bottom piece to keep the upper sheet raised while the central part falls and pushes the air out – the bubble squeeze.

    Third, is to design to avoid the bubbles.

    Fourth is to fire the design layer upside down

    Fifth is to put the design elements on top of the whole piece.

    There are a number of notes on avoiding bubbles on the glass tips blog below.

    Stephen Richard

    blogs at: http://www.verrier-glass.blogspot.com/   and  http://www.glasstips.blogspot.com/

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