What makes glass “spread” ?

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  • #9626
    EclecticTreasures
    Participant

    I have just full-fused a kiln load of “blanks” that I will use as the base for some pendant designs. They were all two layers of glass: some 1 inch square, others 1 1/2 inches square, others 1/2 inches by 2 inches. Some of them maintained their original cut size – while others “spread” and ended up measuring larger than their original size – although they “spread” evenly. For example, one of my 1 inch squares ended up being almost 1 1/8 inches square.

    What makes some pieces get larger while other remain true to the original measurements? How can I keep the spreading in check?

    Thanks,
    Barb

    #12028
    Anonymous
    Inactive

    At fusing temperatures, the glass will naturally flow until it is about 1/4″ (6 mm) thick. That’s two layers of typical glass.  If you stack three layers, it will flow. If you put in one lone layer, it will draw up.

    This is caused by surface tension in the molten glass.  It is the same force that causes water to bead up on your kitchen counter.  When you put more water on the counter the drops don’t get taller – just wider.



    Paul
    FusedGlass.Org
    Helios Kiln Glass Studio
    PaulTarlow.com

     

    #12029
    Juno123
    Participant

    Bullseye Technote #5 helped me with this (Volume & Bubble Control).  It has good diagrams and explains the process well.  You could try to look it up on the internet; I got a technical Bullseye Book at my local glass company.  You could dam the peices to keep them from spreading.  Hope this helps.

    #12030
    EclecticTreasures
    Participant

    Ahh- that makes sense as to why some of my pieces get larger than others – glass thickness or number of layers.

    This is such a great forum – ask a question – get an answer!!!

    Thanks, Paul!

    Barb

    #12031
    EclecticTreasures
    Participant

    Great resource! Thanks for pointing me in the right direction. I have looked at the Bullseye Education site before, but had forgotten about it. It’s in my bookmarks now!

    Thanks again,
    Barb

    #12032
    steve worcester
    Participant

    Understand that it only is relevant to undamned pieces. If you shore up the sides (technically) it will maintain that approximate height (thickness)

    Steve Worcester

    http://WWW.TURNINGWOOD.COM

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