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What about ammonium persulfate ? when I worked at the electronics plant that was what we used to etch our boards. It is clear and turns blue as it etches . we used to put it in a corningware baking pan and warm it with a hot plate underneath . if you put more into the mix it of course eats away the copper faster. In time it will take the shine off the corningware in the area where the heat source was.
Have also used ferric chloride , it also works better if you warm it. Ferric chloride is usually used in sewage treatment plants to coagulate the solids.
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Friday, May 27, 2016 8:07 PM
To: Homebrew_PCBs Mailing List
Subject: [Homebrew_PCBs] Substitute for Sodium Persulphate
I have a commercial etching tank, composed of formed acrylic plastic
and two fish tank pumps.
It's designed for sodium persulphate etchant.
I can get a pool shock persulphate etchant for about 10 dollars for 1
KG, and you need about 1 KG for a single run (no idea how many boards
that is, but it's about 1-2 gallons of etchant).
The normal HCl/H2O2 etchant that I use would no doubt eat the pumps to
pieces.
So a question would be: Can I use high concentration H2O2 (say from a
beauty supply store, no idea how much that might be, but presumably
less than the 1.25 dollars/quart that I can get H2O2 for...)? Just by
itself, I suspect that it might not work, would activating that
etchant with a little chloride ions (perhaps salt?) work?
Has anyone looked for a substitute for Sodium persulphate (potassium
persulphate will also work, but equally expensive, I think)?
Is there an etchant that will work for this kind of situation?
Harvey