Interesting. What about the liquid stuff? I have seen an application technique where you put a dollop in the center of your board, cover it with a piece of cellophane, and then squeegee it out to the edges. I don't even think you need to wait for it to dry, you expose it right through the cellophane.
That's the theory. The practice is it's a complete PITA to work with the liquid stuff, very messy, hard to get a good smooth surface without bubbles, exposure time varies radically with colour, thickness of application etc.
There was discussion on this list recently about air-brushing it on and pre-baking to dry it before exposure which would give better results, but you need to quite precisely control the temperature (apparently, I can't reproduce the results yet, don't have a good enough oven) in order to hit a temperature which will dry it, but not kill it's ability to cure.
For very small boards it's not too bad, but anything over 2 or 3cm per side, it's just frustration city for me.
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Re: [Homebrew_PCBs] Fiberglass weave present through copper surface? (plus some tips I learned...)
2014-05-15 by James