Where the ceiling had been punched open for ceiling supports, patching was done with wire mesh and plaster before a skim coat was applied to the entire ceiling. In areas where the brick had deteriorated, wire lath was used to create a sound surface and a level wall. In the Manhattan Brownstone project, a variety of methods were employed, including plastering directly over the existing brick walls that were first treated with a blue bonding agent. Sometimes they can use the brick surface that remains, sometimes they must affix wire lath to the brick to serve as a support for keying the new plaster. “Our crew makes a determination on an individual basis,” Annino says. The plaster crew must first assess the existing walls, masonry, or ceilings that need to be plastered. The quality of any plaster job and the degree of adhesion depends, in large part, on the integrity of the surface on which it’s applied. “Each plaster job is unique,” Annino says. Master plasterers work with a spray bottle to keep the plaster wet as they smooth it to a perfect finish. At this point it is ready to be mixed into putty. The reaction is complete when the slaked lime stops giving off heat.Once poured in, the lime and plaster mix is left to “slake” or sit and transform itself.The measurements are inexact to the untrained eye, but very precise to the plasterer who has to “feel it out,” as Gary Annino of Boro Plastering explains. Into this circle he pours water, and then sprinkles the water with plaster.First the plasterer creates a “gauge” that is a circle of putty, banked up like a swimming pool, on the mixing board.This lime putty is used for the finish coat of plaster that is skimmed onto the wall and smoothed to create a hard, shiny finish coat. “This is where art meets science,” Bob says, as he watches the mix being prepared for the lime putty. With a traditional lime finish coat, the plasterer becomes a chemist. Finish coat: The third and final coat is an application of lime putty, which gives plaster walls their smooth, hard, shiny finish.The sand provides a rough texture that gives the light, 1/8-inch finish coat a surface to grip onto.

Brown coat: The second rough coat is made of the same mixture and is called the “brown coat.” The brown coat is applied directly to the scratch coat, also at a 3/8-inch thickness, but left unscored.Scratch coat: The first coat is called the “scratch coat” and is applied at 3/8 inch thick then scratched or scored with a comb to give it a rough texture.

Boro Plastering works with a ratio of three-to-one, bags of sand to bags of gypsum, for their rough coats. Many firms now work with gypsum since it eliminates the need for added fiber and has a much quicker set up and drying time. The lime is typically derived from limestone or ground oyster shells. These coats form the base of the wall and are mixed of lime or gypsum, aggregate, fiber, and water. The three-coat plaster system begins with two coarse or rough coats.

Applying veneer plaster