Have you tried using the screen cleaner solvent that's specifically
made for removing the photo emulsion from silkscreens? I have no idea
what chemicals are in it. If it can remove cured emulsion from a
screen, it should certainly work on a PCB.
Regards, Bob
--- In Homebrew_PCBs@yahoogroups.com, "hjf2k2" <drgenio@h...> wrote:
<snip>
>
> But, the expired emulsion leaves a nasty residue, as if it's still
> stuck to copper. No problem. Fine steel wool makes it go away. Even
> pushing (relatively) hard to the thin tracks, the artwork stays.
>
> I'm really happy with the results.