The reduction in dust also makes it safer to use silicacious materials for blasting, or to remove hazardous material such as asbestos, radioactive or poisonous products. Process speeds are generally not as fast as conventional dry abrasive blasting when using the equivalent size and type of media, in part because the presence of water between the media and the substrate being processed creates a lubricating cushion that can protect both the surface and the media, reducing breakdown rates. Reduced impregnation of blasting material into the surface, dust reduction and the elimination of static cling can result in a very clean surface. However wet blasting of mild steel will result in immediate or 'flash' corrosion of the blasted steel substrate due to the presence of water. The lack of surface recontamination also allows the use of single equipment for multiple blasting operations—e.g., stainless steel and mild steel items can be processed in the same equipment with the same media without problems. "Bead blasting" is the process of removing surface deposits by applying fine glass beads at a high pressure without damaging the surface. It is used to clean calcium deposits from pool tiles or any other surfaces, remove embedded fungus, and brighten grout color. It is also used in auto body work to remove paint. In removing paint for auto body work, bead blasting is preferred over sand blasting, as sand blasting tends to create a greater surface profile than bead blasting. Bead blasting is often used in creating a uniform surface finish on machined parts. It is additionally used in cleaning mineral specimens, most of which have a Mohs hardness of 7 or less and would thus be damaged by sand. In wheel blasting, a spinning wheel propels the abrasive against an object. It is typically categorized as an airless blasting operation because there is no propellant (gas or liquid) used. A wheel machine is a high-power, high-efficiency blasting operation with recyclable abrasive (typically steel or stainless steel shot, cut wire, grit, or similarly sized pellets). Specialized wheel blast machines propel plastic abrasive in a cryogenic chamber, and is usually used for deflashing plastic and rubber components. The size of the wheel blast machine, and the number and power of the wheels vary considerably depending on the parts to be blasted as well as on the expected result and efficiency. The first blast wheel was patented by Wheelabrator in 1932. Hydro blasting is not a form of abrasive blasting as no abrasive media is used. Hydro-blasting, commonly known as water blasting, is commonly used because it usually requires only one operator.