SANDBLASTING TIPS
We are not claiming to be experts in the actual finishing
of signs, so we decided that it would be more appropriate to show you an article
that was featured in Sign Builder Illustrated, issue #27.
The following text is a condensed version of this article,
which was written by West Jenkins who was sales manager of the Sandblast Division
of Anchors Stencils.
GETTING INTO SANDBLASTING
SANDBLASTING SIGNAGE: A PROFITABLE ALTERNATIVE
Sign makers who are looking for a profitable way to
expand the styles of signs they offer should consider sandblasted signs.
In markets often dominated by one-dimensional vinyl graphics and electrical
signage, the multi-dimensional sandblasted signs are distinctly different
and very appealing.
MARKET GROWTH
The re-emergence and growth of sandblasted signage
in the USA has been tremendous and is spreading quickly around the world.
No longer considered just for the rustic, woodcraft oriented business,
sandblasted signs are found in professional office buildings, resorts,
golf courses, hotels, restaurants, and major residential developments.
Clear heart vertical grain redwood has long been
the substrate of choice because of grain definition, and ability to weather
well. New restrictions on logging redwood and skyrocketing prices have
forced sign blasters to consider other woods, as well as other substrates
that are now available for sandblasting. In parts of the USA and in other
countries where redwood is not available, another softwood, cedar, is being
used.
GETTING STARTED
Let's take a look at the general process and parameters
for successful and profitable sandblasted signage and options for getting
started.
Regardless of the substrate you choose, the process
and guidelines for sandblasting are much the same.
The key to efficient and profitable sandblasting
is having the right equipment and materials. Not many sign shops can afford
the expensive compressors, pressure pots, and various equipment accessories
needed to get started. There are, however, many options available.
- Option One is to subcontract the blasting phase of the project to a commercial
sandblasting operation. That is the most common practice. Note that most
commercial blasters are accustomed to working on metal surfaces and brick
or concrete buildings. They require higher pressure and coarser grits of
abrasive than is needed for wood, glass, etc. If you choose to subcontract
your work, it will pay to talk to the blaster and arrange lower pressure
and finer abrasives.
- Option Two is to subcontract your work to a monument
or stone blaster. Some monument blasters use metal abrasives for granite
blasting and may not use sand. Ask up front for clarification on this.
Metal abrasives are fine for many substrates like glass, tile, and acrylics,
but not generally recommended for wood.
- Option Three is to rent the equipment yourself.
Safety concerns, shop location, and some regulations on sandblasting may
make this option unfeasible.
- Option Four is to purchase a small self-contained
blasting cabinet and blast small signs yourself.
PREPARING THE SIGN BLANK
Many times, the customer will make the decision of what
type of sign substrate to use. If you have samples or photos of different
substrates, you may be able to recommend one of these to your customer.
STENCILS FOR SANDBLASTING
When preparing your sign for sandblasting, the choice
of sandblast resist of "stencil" is very important. The type of sandblast
stencil most commonly used is a natural rubber compound. These rubber stencils
are coated with different types of adhesives for different applications.
"High Tack" stencils are coated with an acrylic adhesive for use on raw
wood.
The sandblast stencils come in various thicknesses
and computer cut styles. The computer stencils come punched or unpunched
for both sprocket fed and friction fed cutters. Most cutters perform better
on rubber stencil when using a 60 degree cutting blade instead of the normal
30 degree blade used for vinyl. The thinner 18 mil (thousandths) stencils
are used for glass and plastic blasting. The thicker 30 mil stencils are
used for wood and stone blasting.
Once you have the right stencil for your substrate,
the application procedure is relatively simple. Always make sure that the
sign surface is dry, and free of dust or dirt. If you are using the hand
cut stencil, simply peel the easy release liner off the back, and apply
the stencil to the sign surface.
Smooth the rubber out with a vinyl squeegee or your
hand to eliminate air bubbles. The stencil should then be rolled down good
with a hard rubber brayer or some kind of rolling pin.
Once the stencil is on the surface, then draw your
designs on the stencil and cut them out with an exacto knife. Shops that
have computer cutters can use them to cut the stencil. The computer stencil
is processed similar to vinyl. Cut it; weed it; transfer it to the sign.
You are now ready to have it blasted.
BLASTING
As mentioned earlier, during the blasting phase you should always use the
recommended air pressure and abrasive grit for best results. For most wood
blasting, 70-80 PSI (on the pressure pot gauge) is sufficient. Recommended
sand grit size is a 30-70 mesh, or fine grit.
Most blasting except for glass etching will require
a minimum compressor size of 10 to 15 horsepower. Just remember, it is
better to have too much air rather than not enough. A quick reference for
determining (CFM) cubic feet per minute required is as follows for an average
blasting set-up:
| nozzle dia. |
CFM |
CFM |
CFM |
CFM |
CFM |
| 1/16" |
3.1 |
3.6 |
4.2 |
4.7 |
5.6 |
| 1/8" |
12.3 |
14.5 |
16.8 |
19.0 |
21.2 |
| 3/16" |
27.5 |
32.8 |
37.5 |
43.0 |
47.5 |
| PSI |
40 |
50 |
60 |
70 |
80 |
FINISHING
After the blasting is done, it is time to finish the
sign and install it. On most wood signs, the letters and designs are painted
with enamels, while the background is painted with latex, or in many cases
covered with an oil based stain. The debate over latex versus enamel is
ongoing, however, either will work for your wood signs.
Installation can be a really tricky part of the job
so be very careful when estimating installations of sandblasted signs.
The sign maker now has good, profitable alternatives
to vinyl or electrical signs. Sandblasted signs can give you a unique advantage
when bidding on sign jobs. It will take some experimenting and practicing,
but you can use some of the test pieces as samples to show your potential
customers.
You should contact some of the business developers and architects
in your area to let them know what you have to offer. Don't wait until
the ground has been broken at the construction site: by then, the signs
are already spec'd in — and you are spec'd out.
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