There are many ways of removing paint, rust, dirt and other coatings from surfaces. In some cases the material to be removed just does not belong there, such as graffiti. In other cases, the material should be removed before the surface is recoated, a process which is commonly referred to as surface preparation. Within the context of surface preparation there are many types of equipment and technologies, from very simple to very complex.
One of the most common methods, especially involving large surfaces, is sandblasting. This involves bombarding the surface to be cleaned with an abrasive material at pressures that typically range from 20 psi to 150 psi. The friction caused by the abrasives hitting the surface has essentially the same effect as the grit of sandpaper applied over a surface area under pressure.
The three most widely used methods of sandblasting are dry blasting, slurry blasting and vapor abrasive blasting. Each of these methods uses a pressurized blast pot. During the operation of the system, air or water is constantly introduced into the pot to maintain pressure. The material within the pot is then forced through a blast hose to perform its intended function.
Dry blasting – Abrasive material is loaded into the pot, which is then pressurized with air.
Slurry blasting – Water is added into the pot with the abrasive material, then pressurized with air.
Vapor abrasive blasting – As in slurry blasting, both water and abrasive fill the blast pot. Unlike the other two methods, the pot is then pressurized with water.
An important distinction is that air can be compressed, while water cannot be compressed. Our next installment will discuss the effects of air vs. water pressurization.