Sandblasting uses pressurised air to spray abrasive grit against a surface at high speeds. This grit chips away steadily at the surface being sprayed, allowing finishes to be stripped or stone to be engraved. The term "sandblasting" is in fact a bit deceptive, since regular quarried sand will usually clog a blasting machine. Instead, sandblasters use aluminum oxide powder or special hardened silica sand. Although often used to strip softer materials such as paint, a sandblaster can also cut into granite; workers carve designs on granite tombstones this way.
Buy a sandblasting attachment for your air compressor if you have one. You can also rent sandblasters from most large home improvement stores. You can buy the grit necessary for sandblasting from the same supplier. You'll need large amounts. Sandblasting a whole car chassis of its paint, for example, uses about 200 litres of grit. Carving a large design into granite or stripping the finish from a large area of granite will use a similar amount.
Connect the sandblasting nozzle to the air hose coming out of the compressor. These hoses have threaded connections that screw into the base of the nozzle assembly. Rented sandblasters will often be pre-assembled.
Filter your abrasive grit by pouring it through a fine kitchen sieve. This removes any chunks that can foul the lines of the sandblaster.
Surround the granite to be blasted with tarps. These will catch the sprayed sand for reuse, and protect the surrounding area from the dust released by the blasting process.
Mark out any design to be blasted on the granite by drawing the design on a silicon rubber sheet, then cutting the design out with a sharp knife.
Attach the stencil to the granite surface with rubber adhesive. Sand blasted at it will bounce off the rubber, but will etch the exposed areas of the design.
Load the sandblaster's sand hopper to the fill line with abrasive grit.
Pressurise the air line to 45.4 Kilogram per square inch.
Put on safety goggles and a dust mask. The dust from blasted stone can damage both your lungs and your eyes.
Squeeze the trigger on the blasting nozzle to release the stream of sand. Hold the nozzle a few inches above the granite surface and move it in slow, steady strokes until you've removed as much stone as you wish. You'll likely need to refill the hopper several times during this procedure.
Shut off the sandblaster by releasing the trigger and closing the pressure valve. Bleed out the last bit of the line by squeezing the trigger for a few seconds after shutting the air supply off.
Peel off any rubber stencils applied to the granite to reveal the etched-in design.
Things you need
- Air compressor
- Abrasive grit
- Silicon rubber sheet
- Rubber adhesive
- Dust mask