Like cement, plaster is a mineral-based substance used in building construction for ceiling, walls and decorative finishes. The calcium sulphate variety, also known as gypsum plaster, is one of the most widely used building plasters. It starts out as a dry powder that is mixed with water to create a malleable, thick paste. Plaster can be difficult to cut because it cracks and chips very easily. When cutting into a plastered wall, a contractor might use a blade, saw or drill.
A hand-held razor blade is one of the more rudimentary, yet effective tools used to cut plaster says Steven Bliss in his book, "Troubleshooting Guide to Residential Construction." Builders use the thin blade to precisely cut through a plastered wall or plasterboard's layers. When cutting plasterboard, which is a liner board coated with a thick layer of plaster, a blade can be used to cut through the surface, allowing the board to be easily broken along this scored line. An expedient plaster-cutting method, the razor blade is widely used because of its effectiveness and convenience.
High RPM (rotation per minute) spiral-cutting tools are used to cut plaster, because they tend not to rattle or loosen the rest of the plaster. This tool is helpful when trying to cut into a wall, as it is less likely to disturb the integrity of the structure. According to "Home Improvement 1-2-3," the blade needs to come to full speed before attempting to use it on the surface. Furthermore, having extra blades on hand is recommended, as blades tend to dull quickly when working on plaster.
Drills are traditionally used to create holes in surfaces, but with skill they can also be used to cut plaster. As with the spiral-cutting tool, the high RPMs will keep the drill from altering or disrupting the state of the rest of the plaster. The trick is to puncture holes into the plaster along the desired cut line. Keep the holes close together and, when finished, apply slight force to break apart the structure. The drill can be effective in cutting holes in plastered walls, or dividing plasterboard.
A sabre saw is a powered or electrical hand-held saw, used in construction to cut a multitude of materials, including plaster. The "Popular Mechanics Complete Home How-To" recommends using a fine-tooth blade when using the saw on plaster. The reason for the blade is the plaster's high propensity to chip and crack when being sawn, due to the vibrations the saw makes when cutting through the wall. Pressing hard against the wall can reduce the vibrations, and thus the likelihood of creating fractures.