Sand blasting is perhaps the most commonly used blasting system in industrial painting. Abrasive particles of sand are mixed with a high pressure stream of air or water. The resulting mix is sprayed on a painted surface. The action of sand and high pressure air or water readily cleans most surfaces of paint and dirt.
Sand blasting is an excellent blasting method to prepare painted concrete and masonry. For softer materials such as wood, special equipment must be used to prevent damage to the substrate. Wet blasting, done with high pressure water sprays, is usually done to exterior surfaces. Dry blasting, which uses high pressure air as the grit propellant, is most often used to prepare metal surfaces.
As an abrasive material, sand is cheap and readily available. Although native sand, sand from a local source may be used, cleaning the material to remove impurities is highly recommended. Also, the granule size and composition of native sand can vary considerably, which makes achieving uniform results a little trickier. Many professional contractors use aluminum oxide or silicon carbide grit that has been cleaned and sifted for uniform particle size.
Like many blasting procedures, sand blasting is of limited use against areas that are thickly coated with paint. Thicker finishes should be scraped before shooting the structure in order to preserve the substrate.
Like steel shot, the sand can be cleaned and reused if desired. An extraction system reclaims the sand particles by showering the sand and paint impregnated air with water. A filtering system removes the dirt and paint and leaves the sand particles for reuse.
Coming Up: Water Blasting in Detail
