Sandblasting is a process that's typically used to remove paint or inscribe messages on stone. High speed particles of grit (formerly sand) are blasted at a surface, and the grit then grinds away the surface material. A number of alternatives to sandblasting exist, and many of them are a great deal more environmentally friendly.
Though it might sound like it would be worse than using sand, recycled glass grit has been successfully substituted for sand in the sandblasting process. The glass is extremely tiny. Unlike sand particles, the glass particles are much heavier, and they won't dust up in the air and cause irritation to the eyes and lungs. However, you still must wear safety equipment to protect your eyes, face and lungs from accidentally coming into contact with the glass particles.
Another alternative to sandblasting is to use high pressure water. Keep water under extremely high pressure, and spray it against a surface with a force great enough to peel paint or to clean grit out of concrete pores. Using water instead of sandblasting is much safer environmentally since water doesn't harm the environment, and you don't have to clean it up; it will evaporate in time. Additionally there isn't anything added to the water throughout the process; it's just pure water under high pressure.
Dry ice blasting is also an option you can use over traditional sandblasting methods. You must keep dry ice has at extremely cold temperatures, but you can freeze it into very small particles. You can fire these particles at a surface to act as an abrasive, but the dry ice evaporates completely in a short period after it strikes the surface. As such, dry ice as an abrasive requires no real cleanup, and it doesn't pollute the environment; however it is more expensive than sand and other silica-based grit, and dry ice is harder to keep cold and ready.
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