float or plastic float is used to rub down the walls. Traditionally, water is splashed on walls using a coarse horsehair plasterers brush followed by immediately rubbing the float in a circular or figure 8 motion although a figure of 8 can leave marks. Many modern plasterers use a hose with a special nozzle with a fine mist spray to dampen walls when rubbing up (using a wood float to bring a consistent finish). Using a hose brings a superior finish and is more consistent in colour as there is more chance in catching the render before it has a chance to harden too much. After the work area is floated, the surface is finished with a wet sponge using the same method as floating with a wood float, bringing sand to the surface to give a smooth consistent finish. Materials used in the render are commonly local sands with little clay content with fine to coarse grains. Sand finish is common for external render and may be one or two coats. Plasterers use a t-bar to screed the walls until it is plumb, straight and square. Two coat is superior as, although more expensive, it gives a more consistent finish and has less chance of becoming drummy or cracking. Drumminess occurs when the render doesn't bond completely with the wall, either because the wall is too smooth, a coat is too thick, or the coat is being floated when the render has hardened too much, leaving an air space that makes a drumming sound when a metal tool is "rubbed" over it. For internal walls, two coats is the standard and follows the same method as for external rendering but with a weaker mix of five or six sand to one cement and one lime. However, instead of being finished with a sponge, the second coat is left rough and sometimes will be scored by nails inserted in the float. After drying, the surface is then scraped to remove loose grains of sand before plastering. If the walls are concrete, a splash coat is needed to ensure bonding. A splash coat is a very wet mix of two parts cement to one part sand that is "splashed" on the wall using the plasterers brush until the wall is covered. Special mixes are sometimes required for architectural or practical reasons. For example, A hospital's X-ray room will be rendered with