Article
Traditional lime plaster has been used for centuries to create durable, breathable, and aesthetically pleasing wall finishes. It remains a preferred choice for restoring historic buildings and achieving eco-friendly construction. The process of applying lime plaster involves several distinct steps, each requiring careful preparation and execution to ensure a long-lasting and professional finish. Below is an outline of the methodology used in plastering internal walls with traditional lime plaster. The first step in lime plastering is surface preparation. The substrate must be clean, stable, and slightly roughened to provide good adhesion. Common substrates include stone, brick, or lath (a framework of wood strips). For existing walls, any loose or flaking material must be removed, and large gaps or holes should be filled with a compatible material. The surface is then dampened to prevent the lime plaster from drying out too quickly, which can lead to cracking. For wooden lath substrates, soaking the laths can further improve adhesion and workability. Next, the lime plaster is mixed. Traditional lime plaster typically consists of lime putty, sand, and sometimes hair or fiber for added strength. Lime putty is made by slaking quicklime with water and aging it for several weeks to months. The ratio of sand to lime putty is usually around 3:1 by volume, though this can vary based on the specific application and desired texture. The mixture is thoroughly combined to ensure uniformity and consistency, with the addition of water to achieve a workable paste. The application of the plaster is done in multiple coats. The first, or scratch coat, is applied directly to the substrate in a relatively thick layer and scratched with a comb or notched trowel to provide a key for the subsequent coat. This layer serves as a base and helps bond the plaster to the wall. Once the scratch coat has set but is still damp, the second, or float coat, is applied. This layer is thinner and smoothed with a float to create an even surface. For high-quality finishes, a third, or finish coat, may be applied. This final layer is very thin and can be polished or textured as desired. Curing is a crucial final stage in lime plastering. Lime plaster hardens through carbonation, a process where lime reacts with carbon dioxide in the air to form calcium carbonate. This process is slow, requiring several days to weeks, depending on humidity and temperature. During this time, the plaster must be kept moist to ensure proper curing and to prevent cracking. This is often achieved by misting the surface with water and covering it with damp hessian or plastic sheeting. In conclusion, plastering internal walls with traditional lime plaster is a skilled craft that combines historical techniques with modern materials. Its benefits include breathability, durability, and a natural aesthetic that suits both heritage and sustainable building projects. By following the proper methodology—from surface preparation to curing—craftsmen can achieve a finish that not only looks beautiful but also performs exceptionally over time.
