Hello again folks. I’ve been etching copper using a ferric chloride
solution. I got the stuff in a kit that was designed for etching
custom printed circuit boards. With practice, I am finally starting
to have some successes but I’m also noticing some problems that seem
to be fairly common. I think these may be related to the different
resists I’ve tried. Let me explain what I’m doing and what I think
is going wrong and I’d really like to hear from others with an
assessment of my notions.
I’ll start with resists. The kit suggested using a permanent felt
tip marker ( I used a Sharpie). It seems that the ink does act as a
resist but I’ve noticed that it is very difficult to get a good even
coat with the ink. Variations in the ink coating result in
"etch-through" giving me smudged looking results. To get the depth I
want requires etches of 2-3 hours. I decided to try a laquer (
common fingernail polish, somewhat thinned). This gives very good
protection but presents problems of it’s own. When I have to scratch
a design through it, the final etch shows that there may have been
some lifting of the laquer around the scratches. The mordant appears
to be seeping under the resist around those lines giving an uneven
etch and fuzzy line margins. I want clean, clear lines.
My assessment of the laquer is that it needs a better bite on the
surface to prevent lifting. Perhaps I’m putting too fine a polish on
it prior to resist application? Another consideration I’ve had is
that perhaps the laquer is forming too hard of a coat causing it to
lift like a sheet when I scratch through it. The ink resist seems
too inconsistent. I’ve tried multiple coats but the solvent in the
pen dissolves the previous layer causing smearing that eventually
shows through on the etch. The ink doesn’t seem too well suited to
long etch times either. Would it help to go with a resist that has
more “tack” to it? Maybe something like beeswax or a thinned rosin
or tar? Any ideas would be appreciated.
A final question concerns the mordant. Are there other concoctions
that might work better? I’ve looked into buying some nitric acid and
constantly run into people who want to know if I’m trying to build a
bomb. Lunatics. I just want to play with metal.
Mike