down to the Nuts & Bolts of blasting
The equipment required for sandblasting is really pretty basic:
an air compressor, a container for the abrasive and a nozzle. There
are, however, more than a few variables involved with these three
elements! I'll briefly cover them here which should be enough to
get you going if you?re interested in trying this art yourself.
The compressor provides the air that operates your sandblaster.
You will find a variety of them on the market and the choice can
be quite boggling. I've tried several and will make a few suggestions
to help you in selecting one that will meet your needs.
||Air compressors are rated by CFM
@ PSI. That's Cubic Feet per Minute at Pounds per Square Inch.
That may not mean much to you and that's OK, just look for the
rating number and stay above 6CFM @ 100 PSI free air. You may
find a couple different ratings for a compressor. It may say
it's rated at 7.6 CFM, but you need to look for the "free
air" rating, which, at 7.6 CFM would only be about 4.9
CFM @ 100 PSI free air. To stay in the range you need to sandblast
with any efficiency, you should be looking at nothing less than
a 3 HP compressor. Currently I'm using a 5HP that delivers 9.0
CFM @ 100 PSI free air, which is rated at 15.4 CFM. Confused
yet? All in all, you can expect to pay between $250 (left) and
$1,200 (right) for your compressor.
The second compressor consideration is the size of the tank. The
larger the tank, the less the compressor has to run to fill it up.
It's not necessarily good to have the compressor running all the
time - that's a sign that you're not getting all the air you require.
I started with a 20 gallon tank, and the compressor ran quite frequently.
I moved up to a 30 gallon and the compressor runs about a third
of the time. Finally I gave up and went to the 85 gallon (above,
right) as I was blasting several hours at a time and needed all
the air capacity I could get.
One thing to be very careful about is the air filter on the compressor.
I learned this the hard way by blowing one out of the water. My
abrasive got into the motor and literally chewed it to pieces. My
next compressor had an industrial, metal contained cartridge filter.
You need to keep the compressor as far away from your work as you
can. In another room is ideal but not always possible. But at least
try and route the intake to another location (or outside) to be
All you need is a length of hose to get to your job and you're
set. Ah, another detail! Keep the hose as short as possible for
two reasons. First, the longer the hose, the greater the drop in
air pressure from your compressor to your work. Secondly, the longer
the hose, the more opportunity for picking up unwanted moisture
which can wreak havoc with your abrasives!
And speaking of moisture, it's a necessary task that when you're
done with a job, release the pressure from the tank through the
release valve under the tank. This will blow out any standing water
that gathers in the tank. Another necessity is a water filter for
the hose line. Many compressors have one at the tank which is nice,
but remember your hose is also collecting moisture. Depending on
the equipment you use to sandblast, move the water filter as close
to your working end as possible.
Before we move off of compressors, I should share with you that
the larger ones will usually run off of 220 volts. Not a nice surprise
to discover as you are unpacking your new toy. So be prepared. Some
of the small compressors can be rewired to run off 110 volts, but
I'd shy away from this lower end compressor. They can work fine
depending on what you want to do, but I insist on a good, high pressure
air flow and lower end compressors don't always provide that.
If just by chance you happen to have an old gas compressor out
behind the barn, remember that a gas compressor only puts out about
60% of the CFM that an electric compressor does. So don't think
because you have a 5HP gas compressor it is equivalent to the electric
model - it will only rate comparably to about a 3HP electric.
There are basically two types of sandblasters, siphon feed and pressure
pot. They work much like their names. The siphon feed pulls the abrasive
from the container using suction power that is created in the sandblasting
gun itself. Air is passed over the hose end that leads to the abrasive,
creating a suction, and then the abrasive is mixed with the air and sprayed
out the nozzle.
The pressure pot works a little differently. Here the abrasive is put
under pressure and forced out of the container in a controlled flow and
mixed with the air at that point to force it up the hose and out the nozzle.
The basic difference is in the pressure with which the abrasive leaves
the nozzle and its impact on your target. The pressure pot, working under
far less pressure than the siphon method, produces much greater pressure
at the nozzle. You might achieve the same pressure results with a pressure
pot at 10 PSI as you would a siphon process at 85 PSI. Big difference!
You might also notice the difference in the nozzles between the two.
I find the gun type much easier to handle than the straight nozzle. I
use both depending on the project and how much pressure I will need.
Both nozzles have ceramic tips. This reduces static and extends wear.
Ceramic does wear down and loses its ability to constrain and direct the
flow of abrasive. In either case, you can get many hours of use before
having to replace them.
Here are two types of blasting guns. The one on the left I use with my
siphon system. Notice that it has two hoses running into it; one for abrasive
and the other for air. You can pick them up from most hardware stores
for about $40 including the hoses and pickup tubes that go into the abrasive.
The gun in the middle is a PAB blasting gun. It replaced my small airbrush
pencil type gun. It comes in two feed hose sizes, 1/4" and 1/8"
and a variety of nozzles for both. Works like a champ - I love it. This
has a carbide nozzle that wears about 10 times as long as the ceramic
and costs a bit more too. I have even carved designs in light bulbs! Why
you might ask? What else do you do with burnt out light bulbs? Check my
suppliers page for more info on the PAB gun.
The gun (nozzle) on the right is the standard that comes with many sandblasting
setups. I use it all the time, it's a great work horse. Both of these
last two guns only have one hose, thus they run off the pressure pot and
the hose carries the abrasive under pressure from the pressure pot.
Price wise, you can find siphon systems from$30 to $60 depending on volume
and I built my own for $5 and a few scraps around the garage. I used a
copper fitting to come out the bottom of the bucket and I added a couple
very small holes to allow air to mix with the abrasive before it begins
its trip up the hose. By covering or opening the holes you control the
amount of abrasive that is sent out the nozzle.
The pressure pots are a different story. They will run from about $80
on up. They hold around 10 pounds of abrasive at the smaller end and withstand
up to about 100 PSI - just in case you want to blow a hole through the
foundation of your house! For my own use, I have two 40 pound capacity
tanks and I end up refilling them more often than I care to.