Before the plaster sets, they scratch its surface with a rake-like tool to produce ridges so the subsequent brown coat will bond to it tightly. Laborers prepare a thick, smooth plaster for the brown coat. Plasterers spray or trowel this mixture onto the surface, then finish by smoothing it to an even, level surface. For the finish coat, plasterers prepare a mixture of lime, plaster of Paris, and water. This mixture, which sets very quickly, produces a very smooth, durable finish.
Plasterers also work with a plaster material that can be finished in a single coat.
This thin-coat or gypsum veneer plaster is made of lime and plaster of Paris and is mixed with water at the job site. It provides a smooth, durable, abrasion resistant finish on interior masonry surfaces, special gypsum base board, or drywall prepared with a bonding agent. Plasterers create decorative interior surfaces as well. They do this by pressing a brush or trowel firmly against the wet plaster surface and using a circular hand motion to create decorative swirls. Stucco is also applied directly to a wire lath with a scratch coat followed by a brown coat and then a finish coat.