Plaster has been around for many years and the desire to have smooth monolithic walls remains to be the ideal look. We know that 5,000 years back the Egyptians burnt gypsum and then ground it into a powder then mixed it with water for use as a joining compound for the huge blocks to assemble the pyramids.
GYPSUM PLASTER 3 COATS
Traditionally in the UK, gypsum plaster was applied to three coats. The first coat was known as the “scratch coat” which was applied over wood lath or metal lath and put on at a thickness of 1/4″ – 1/2″ in one pass, then scratched with a scarfier or some kind of rake to assist “key in” the next coat. The second coat or “brown coat” was applied the next day or in a few days and long straight edges or “darbies” were used to flatten the wall. This coat was finished smoother but left a little rough to allow a final coat to bond. This second pass was also applied at a similar thickness as the first coat. The third and final coat was the “finish coat”. This last coat of plaster was a much thinner application and in most cases hard troweled to a smooth finish. The finish coat was usually painted but before paint was available, the product was integrally colored or left the natural color of the raw materials. This look is what most plasterers in Coventry “Venetian Plaster”, “Faux Plaster” or “Polished Plaster”.
Most people will today will call any smooth finished wall with color variation “Venetian Plaster”. Venetian plaster is more of a style or strategy of multiple thin coats layered one over the other to create the appearance of depth. Most plaster today is applied straight over prepared drywall and is done in considerably thinner coats. The thickness of the plaster system is determined by the preparation of the drywall substrate. Very thin plaster systems will need the drywall to be finished to a level 4 or 5, or would require a thicker plaster base coat to cover and smooth out the imperfections in the drywall. Thicker plaster systems may not require any taping of board joints and inside or outside corners, and often will require some kind of treatment before applying a finish coat.
OTHER PLASTER FINISHES
These days there are many different plaster materials from which to choose including gypsum, cement, lime, acrylic and even clay. You will need to find the correct product for the particular type of application. Acrylic plaster is not hard to apply, may be patched, is exceedingly durable and the installed price is usually less expensive. The most popular reason to hand trowel plaster is that it is integrally colored and the color is varied to give depth in the wall or ceiling, so color possibilities should be a high priority in picking an interior plaster. Ordinarily, interior acrylic plaster may be tinted to any color imaginable for a really low cost in comparison to clay plaster, gypsum plaster, lime plaster or cement plaster. The reason is that the product is much thinner and the colorants are readily available and inexpensive. Since most all acrylic plaster is manufactured domestically and the coverage surpasses other plasters, it is an economic option for a plaster system.