When building with stone, the process of cutting the stone leaves artifacts, or lines caused by the saw, on the surface of the blocks. They give the cut stone an unsightly appearance. When you're building with a material as expensive as stone, you don't want to see the saw marks. The best way to remove the artifacts is to flame the edge of the stone. Flaming, applying a high heat at high pressure, causes small bits of the stone to flake off, erasing the cut marks. To flame, you need a water-cooled propane torch. You can use a water-cooled propane torch on granite, quartzite, sandstone and bluestone but not on marble, cement, artificial stones or some limestones.
Things You'll Need
Water-cooled propane torch
waterline attached to a 40 psig water source -- a hose attached to most city water sources will normally have high enough pressure
100-lb. propane tank with an adjustable pressure regulator
Oxygen tank with an adjustable pressure regulator
Secure the stone to be flamed so that it sits firmly on the work surface or the ground and won't create a falling hazard if it cracks apart. The work surface must be nonflammable.
Read the instructions for the water-cooled propane torch, including all warnings, carefully before starting.
Chain the propane and oxygen tanks to an immovable object such as a tree to prevent the tanks from toppling or taking off like a jet. Wrap the chain around the middle of one tank and the tree or other secure object, and hook the chain snugly with a piton. Repeat with a second chain around the other tank.
Attach all hoses tightly to the water-cooled propane torch including the water hose, the propane line and the oxygen line.
Turn on the water supply and ensure water is flowing freely. Turn the propane regulator to 40 psig and the oxygen regulator to 70 psig. These settings may vary depending on the manufacturer of your water-cooled propane torch; follow manufacturer's instructions.
Ignite the water-cooled propane torch. Place the dial in the start position, turn the mouth of the torch away from anyone or anything flammable and squeeze the flint striker near the mouth of the torch.
Firmly grip the torch and brace yourself for the push-back that the torch exerts when running in wide-open mode; turn the dial to run.
Brush the tip of the flame against the stone edge at 10 degree to 25 degree angle while the water cools the stone. Move the flame forward across the rough edge of the stone at 1/2 foot per minute for a 6-inch stone edge, or faster for thinner pieces, to reduce the risk of the stone heating and cracking. The angle that you flame the stone may vary depending on who made your water-cooled propane torch; always follow the manufacturer's recommendations.
Test the flaming process on broken or scrap bits of stone before using it on the finished stone product. Most city water sources, such as a garden hose faucet, will have sufficient force to reach 40 psig. If you do not achieve sufficient force, but still have some water flow, there will not be a safety hazzard as water-cooled propane torches have a pressure sensor which will turn off the torch.
Use proper safety equipment when working with torches, including goggles, earplugs, fireproof gloves, steel-toe shoes and a respirator. Tie back clothing and hair before working with a torch. Turn off the torch if the cooling water flow stops. Work in an area where the cooling water will flow away safely. Beware of hot stone chip projectiles that can burn you or begin a fire. Remove flammable objects from the work area.