• Sounds like maybe your Thinfire paper is curling.  Try cutting the paper to just 1/4-1/2 inch bigger than the glass.  Papyros doesn’t seem to curl.
    Or, maybe you aren’t using 2 layers of 3mm glass?  Only one layer will pull in, dragging the paper with it.  2 layers will stay right there but round out the edges.  3+ layers will spread out.

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