working with basalt columns

["George Graham" <georgergraham@xxxxxxxxxxx>]

Calvin,
First let me say that I'm extremely envious of you. I'd love to get my hands
on some basalt columns.

Removing the patina by sandblasting is probably the easiest way to do a very
hard job. It sounds like you don't have a big enough compressor. You need
one that puts out about 60 cubic feet per minute and gives you 70 to 80 psi.
But, stepping up in equipment sometimes means stepping up in headaches and
expenses. You might find it easier to hire someone who is a professional
sandblaster and has a mobile setup. The single biggest reason why people
don't get good results with a sandblaster is that the air pressure at the
nozzle is to low. The next issue is the abrasive that you are using. You
need to get abrasive that is used for granite lettering. Aluminum oxide that
is used in the monument industry is good. As hard as basalt is, you can't
get away with using the cheap stuff that is commonly used to remove paint
 from sheet metal and wood. In the past, clean sand was used, but we now know
that the dust from natural sand is extremely destructive to your lungs. If
you are doing any kind of sandblasting, use a GOOD dust mask. Finally,
sometimes the patina on basalt can go well below the surface. Sandblasting
may not be the best way.  I like to use a 20 grit carborundum wheel that
screws onto my angle grinder. When I have a lot of stone to remove, my heavy
duty grinder gets used a lot. Basalt is one of the harder stones to work on,
so go with what works the easiest for you.

Take a look at Isamu Nagouchi's work with basalt and granite, if you haven't
already. There is something profoundly elemental that rises to the surface
when a sculptor works in the hard stones. I think it forces us to eliminate
all unnecessary shapes, and get to the point.

If you really must remove that patina that took millions of years to
make,,,, I hope this helps.
Good luck
george graham