Application: Floating the Brown Coat
Floating plaster brown coats knocks off minor variations in the plane, like clinkers or darby marks, fills small holes and indentations, and opens up the surface of the brown coat. Whatever floats across the brown coat, the hand pressure used is minimal. Pressing against the brown coat might create a hole that needs to be filled. If the brown coat is too wet the float will dig into the surface and create a poor base to finish. Minimal pressure and a floating circular motion create the best float job. Floating can be accomplished with wood floats, hard rubber floats, soft sponge floats, or even a 2/4 piece of wood. The type of finish determines the precision and level of quality that preparation of the base demands.
Floating for machine dashed stucco can be done with soft sponge floats bringing out the sand as if floating a stucco sand finish coat. Floating 100% with a hard rubber float is acceptable, but what ever is used knowing that dash coats reflect every variation in the plane is critical to a superior end product.
Floating base coats for a sand finish can be less stringent, but requirements for flatness are the same. If the base is too rough, the plasterer can fill the voids with a scratch and double back method of applying the stucco to gain a superior end product.
If the brown coat has almost set, rodding the walls is the only alternative for straightening the plane. It leaves a coarse open surface with less compressed grains of sand. A well cured scratch coat wet to create even suction for the brown coat and an even set time for floating maximizes your chances of success. If the brown coat has a higher sand to cement ratio, floating the brown coat becomes easier.
For smooth trowelled walls or synthetic finishes applied over Portland Cement Plaster base coats, the brown coat must be almost perfect. Stucco finishes are inert. They do not shrink back into the holes or imperfections in the base coat. Stucco finishes trowelled smooth over a green base coat can provide a perfect base for synthetic materials, filling voids and imperfections, creating the same smoothness characteristics of the weatherproofing base coat and netting application so integral to successful Exterior Insulation and Finish Systems (EIFS).