Step 9: Strip

Picture of Strip
You'll need sodium hydroxide (NaOH) for this--this is the stuff that Brad Pitt uses to burn Edward Norton's hand in Fight Club it dissolves fat, and your skin is composed largely of fat, so be careful. Check local chemical supply houses--I lucked out: my neighbor makes soap, so I just popped over and asked if I could borrow a cup of lye!
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sleemanj2 years ago
I'd like to add, that in my recent experiments with dry film, I didn't use Sodium Hydroxide to strip it, I just dropped the board in the Sodium Carbonate solution which I had used to "develop" it, and when I came back in about an hour or so, all the resist had simply floated off the board.

I expect that Sodium Hydroxide would work pretty much instantly, but if you can wait half an hour, there seems little point messing with that. Sodium Carbonate (Washing Soda) is perhaps more readily available than Sodium Hydroxide (although both are pretty easy to come by), the stuff I bought was sold as a "natural fabric softener" and is 100% Sodium Carbonate, just look on all the packets of laundry supplies in your supermarket, there's sure to be one hiding there somewhere.

For developing, about 5 minutes is the longest I would leave it in the solution, longer than that and it risks damaging the traces too easily. Don't use a scrubbing pad or anything abrasive, the traces can be damaged, just use a wad of toilet paper to firmly wipe the board after it's soaked a couple of minutes.

The hardest part of this process, is getting the film onto the board evenly, without any trapped bubbles or wrinkles or dust, and then getting it through the laminator without it slipping.

NB: I didn't particularly measure the amount of Sodium Carbonate crystals I dissolved, so your mileage may vary.