Probably the most common (and cheapest) abrasive for blasting is
crushed garnet. It has a beautiful light ruby or dusty rose color.
I have used it for years and by controlling the grit size you can
produce wonderful pieces of art with a multitude of shadings and
Another abrasive that I had in my garage for years and didn’t
even know it, was silicone carbide. I had been using it to polish
rocks. By gradually increasing the grit size, it would polish the
rocks over the period of about a month. Silicone carbide is black
for the smaller grits, or a gun metal color for the larger/finer
grits. I noticed when I used it to blast with that I could actually
see a glow where the abrasive hit my glass! Cool! It was sort of
like having a headlight on your blasting gun!
The draw back was that it was SO abrasive that it ate right through
the masks I used in a very short period of time. I was intending
on using it mostly for cutting into stone, so I was using about
an 80 grit. I’m sure the finer grits would have been less
detrimental on the masking. This just meant I needed to upgrade
or double my masking.
What I find myself using mostly now is aluminum oxide. It has a
great cutting ability, leaves the glass smooth as silk when using
130 - 150 grit and retains it’s sharpness. It's not really
much different from the silicone carbide in my opinion -- either
of them work great. The benefit is that they are very reusable and
the grit retains it's sharpness as it breaks down. Over time your
80 grit becomes 100 and then 120 and so on. Not a problem and takes
quite a bit of use.
You can get bags of "playground sand" for only a couple
of dollars. It is great for getting the rust of lawn furniture,
trailer hitches, old tools and the paint from almost anything. However
sand works on the "beating" principle rather then the
For some projects, like dulling the surface on ceramics, you can
get white sand. It's finer and softer than the playground sand.
The Cutting Edge...
Sharpness is the factor of the abrasive that does the cutting for
you. All the abrasives mentioned above have excellent sharpness.
I recycle all my abrasives and reuse them many, many times. Some
of the crushed garnet I have been using for 8 years! The crushed
garnet, however, does break down in time and you find yourself with
a much finer grit than that with which you started. But it does
remain sharp as it breaks down.
The aluminum oxide and silicone carbide I have not found to break
down (or at least very little) and it has retained it’s sharpness
very well over repeated uses on glass and stone.
Sand, on the other hand, has little sharpness to begin with and
breaks down almost immediately. It’s great for getting the
rust of the lawn furniture before you repaint or for special, very
rough, textures on glass - but I don’t recommend it at all.
Price wise, crushed garnet is the most affordable at about $20
for a 50 pound bag. The aluminum oxide and silicone carbide can
run $1.25 to $1.80 a pound. To keep your blaster running for more
than a 10 minute interval before refilling your abrasive you need
at least 20 pounds of abrasive in your siphon blaster or 40 pounds
in your pressure pot. Sand is dirt cheap - no pun intended - about
$2.50 for a 50 pound bag.
Check the Suppliers section in the menu for locations to order
Keeping Abrasive Clean
Cleaning your abrasive before reusing it is very important. Find
yourself a nice piece of filtering material - a doubled over piece
of screen door screen works fine for me. Cut both ends out of a
1 pound coffee can and tape the screen to the outside bottom. Use
this to filter your abrasive before returning it to the blaster
for another use.
Generally, the parts of the glass or stone that you are blasting
off are pretty fine. However, when I do brick or concrete, I find
the chunks get a little large and my filtering process is critical.
I have seen the damage when a chunk of material goes flying through
the blaster and hits the center of a 30" x 40" nearly
completed piece of glass! For you guys out there - yes, there is
an appropriate time to cry over your work!
One last comment, if your abrasive becomes damp you will have problems
with flow control (the amount of abrasive - if any - that comes
out of your gun). Abrasives can pick up moisture from the air so
keep it in dry, room temperature areas or air tight containers.
It can also pick up moisture from the air in your compressor. You
need (as mentioned in the equipment section) a water trap on your
line to remove excess water that accumulates either in your lines
or directly in your compressor. (sometimes more than one trap if
you have long lines from the compressor.
You can dry abrasives by putting them in shallow baking pan in the
oven at low temps for an hour. This cooks the moisture right out
- but the stuff gets real hot so watch it when you handle it!