Homebrew PCBs

sorry, I didn't express myself clearly. the residue is there after
developing but before going into ferric chloride.

to finally remove the emulsion, i do use screen cleaner. but it seems
to attack copper. i was told to use bleach or sodium hydroxide which
can remove the emulsion and won't attack copper... but I'm not so sure
about that. I use paint thinner and a little more work, and it goes
away, and thinner surely doesn't attack copper.

regards,
hernan

--- In Homebrew_PCBs@yahoogroups.com, "Bob_xyz" <bob_barr@h...> wrote:
> 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.