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What
materials are used for etching?
Resists
Hand
cut resists
The primary materials you need for etching are resists and abrasive.
There are many types of resists, and the ones you use should be
picked for the job at hand. If you hand cut your own resists, pick
a self adhesive vinyl or rubber blasting resist that is made especially
for glass. That means the resist will hold tightly while you are
blasting but release cleanly, with no adhesive residue left on the
glass when you remove it after etching.
A thickness
of 4-6 mils is good for surface etching or shading, 8-25 mils thick
for deep carving. (A mil is a thousandth of an inch.) The higher
the pressure you want to use and the faster you want to carve, the
thicker the resist should be. These resists are usually available
in rolls from 18" to 36" wide and 10 to 50 yards long.
They always come with a silicone release backing paper to protect
the adhesive until you are ready to apply the resist. Resists especially
made for glass are somewhat difficult to find, but some etching
equipment manufacturers and glass etching suppliers carry them.
Pre-cut
resists & photo resists
It is much easier to use pre-cut resists or photo resists, because
they already have a design produced and cut out on them. This gives
you perfect results, no matter how many times you do the same design,
and doesn’t require that you enlarge and hand cut your own designs.
Pre-cut and photo resists can produce designs of very high complexity
with very little work on your part. You can use the designs offered
by the stencil companies (like EtchMaster) that make these resists
or you can send your own designs to be made up for you. For more
information on these resists and a selection of patterns and designs,
see the section on Stencils,
under the Learn glass etching portion of this site.
Abrasives
In order to
etch glass, an abrasive has to be as hard or harder than the glass
and the particles have to be rough, with sharp corners and edges.
Glass beads don’t work well at all, since the beads are round and
smooth. Sand works, since it is the same hardness as glass (glass
is primarily made of sand) and the particles are rough, but there
are three major problems.
First,
the sand dust from blasting is very hazardous to breathe, and can
potentially cause silicosis, a fatal lung disease. If you use sand,
you always have to wear a very good respirator and replace the cartridges
regularly. Second, sand particles dull quickly, so
they can’t be reused many times. This means you have to spend more
money on replacing sand. Third, you can't get sand in a fine
grit. The smallest particle size you can generally get with sand
is about a 90 grit. Most etching these days is done with grit sizes
of 120, 150 or finer, to give a beautiful, smooth finish to the
etching. For awards and gifts, 180 to 220 is common. (The higher
the number, the finer the grit.)
The best abrasive
you can use is silicon carbide. While glass is rated between
4.5 and 6 on the Mohs hardness scale (depending on what type of
glass), silicon carbide is a 9.5 (on a scale of 10, with 10 being
diamond). It is reusable until the particles pulverize small enough
to be sucked out of the system as dust. It is a little more expensive
than aluminum oxide (the second choice) but not if you consider
the cost per hour to use carbide, rather than the cost
per pound. Oxide is 9 on the Mohs scale, so it cuts fairly fast,
but creates a lot of static electricity in the cabinet, which will
constantly cause static shocks. In addition, the dust clings tenaciously
to the back of the glass, making it difficult to see exactly what
you are etching. This is very distracting when you are trying to
use the shading technique.
The dust from
both silicon carbide and aluminum oxide are considered to be "nuisance
dusts" rather than a hazardous material as sand is, so they
are both safer than using sand. Since both materials cost less than
80 cents per hour to use, carbide is the professional's choice for
etching glass.
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