I'm more of a printmaker than a jeweler so I've got your answer.
Whatever your etching resist, asphaltum or universal hard ground,
should be a little thicker consistency of water. The bottle of "tar"
that your talking about was probably an old or contaminated bottle
they sent to you. If you want your new etching resist to reach that
consistency pour some out into a container and let it sit for a
while. Maybe after 15 min you'll notice a film start to form on top.
The resist will just get thicker until it fully hardens.
You can paint more than one coat on your piece but your first coat
has to be thick or else it will lift off with the second coat. If you
want to scratch into something with a tar consistency you can't let
it fully dry, but it should be dry to the touch.
A few reasons for the etching ground being so brittle and flaky...
If your bottle was contaminated that could be a reason but a thin
consistency usually means it's fresh.
If you don't degrease you jewelry really well, the resist will
just flake off. Use naptha or rubbing alcohol to degrease.
Oil from your hands will soak into the dry etching resist and
make the resist flake off, too.
Turpentine or paint thinner will not let the resist adhere to
the metal well.
Sometimes the weather has something to do with it. In Los Angeles
its so dry that I usually have 24 hours to work on an etching before
it gets brittle. When I used to live in St. Louis it was much damper
so I could sometimes get a week out of the same resist being on the
Here's a few tips:
I use throw away sponge brushes to apply the ground to flat surfaces.
If your using a brush to apply the resist make sure most of the
solvents you use to clean the brush are gone.
When it gets too thick you can dilute it with naptha NOT turpentine
or thinner. I think home depot carries it but it's pretty toxic.
Instead of buying the concentrated stuff, I keep a bottle of lighter
fluid (for zippos) that contains naptha. make sure to check the
ingredients before you buy it. It's a little less toxic but I
recommend having some ventilation when your dealing with anything
that contains this stuff, including the resist
If you want to try a different etching ground you can get many
different forms from Graphic Chemical. They've got a catalog and
utrect art supply should have it or pearl paint depending if you live
in a big town.
When you use a resist pour some out into a seperate container to use.
Any contact with the air or dipping brushes into the original bottle
will contaminate your resist very quickly. Don't pour back into the
If you leave your metal in the acid for long periods of time the
resist will also flake off because of strong acid.
Some alternative resists are spray paint, sharpie, toner, but you'll
have to experiment with the timing.
There's a book on etching called "Etching, Engraving, and other
Intalio Printmaking techniques" by Ruth Hand that will give you
some ideas as to alternative methods for making a resist. It may
even have some home recipes for resists but I'm not sure. I don't
think the book mentions etching silver but you can experiment with
their techniques. Silver just requires a stronger acid bath than
other metals. Etching is all about experimentation with your timing.
If you have any questions feel free to email me at
firstname.lastname@example.org I hope this could be of help.