An Overview of Plastering and Lime Usage
Construction or ornamentation done using plaster, is referred as plastering such as a layer of plaster on an interior wall or plaster decorative moldings on ceilings or walls. It is also known as pargeting. The process of plastering has been used in building and construction for centuries.
Historically speaking, the earliest plasters known to us were lime-based. Around 7500 BC the people of 'Ain Ghazal in Jordan used lime mixed with unheated crushed limestone to make plaster which was used on a large scale for plastering walls, floors and hearths in their houses. With red finger-painted patterns and designs walls and floors were often decorated. In early Egyptian tombs, walls were coated with lime and gypsum plaster and the finished surface was often painted or decorated while in ancient India and China, renders in clay and gypsum plasters were used to produce a smooth surface over rough stone or mud brick walls. Employment of modeled stucco was done throughout the Roman Empire. The Romans used mixtures of lime and sand to build up preparatory layers over which finer applications of gypsum, lime, sand and marble dust were made; pozzolanic materials were sometimes added to produce a more rapid set.
For plastering the tools and materials consist of trowels, floats, hammers, screeds, a hawk, scratching tools, utility knives, laths, lath nails, lime, sand, hair, plaster of Paris, a variety of cements, and various ingredients to form color washes. While most tools have remained unchanged over the centuries, developments in modern materials have led to some changes. Without staining the finish the application of certain new, acrylic-based materials are done which is allowed by trowels, originally constructed from steel, are now available in a polycarbonate material. Floats, traditionally made of timber (ideally straight-grained, knot-free, yellow pine), are often finished with a layer of sponge or expanded polystyrene.
Traditionally, plaster was laid onto laths, rather than plasterboard as is more commonplace nowadays. Generally being pines wooden laths are narrow strips of straight-grained wood, in lengths of from two to four or five feet to suit the distances at which the timbers of a floor or partition are set. Single (1/8 to 3/16 inch thick), lath and a half (1/4 inch thick), and double (3/8-1/2 inch thick) are the three thickness in which laths about an inch wide are made.
Composition of lime plastering is done by mixing lime, sand, hair and water in various proportions as per the nature of work to be done. For internal plastering is that calcined from chalk, oyster shells or other nearly pure limestone, the lime mortar principally used and is known as fat, pure, chalk or rich lime . Plasterer also used hydraulic limes but mainly for external work.
Wet and dry are the difference between traditional and modern plastering. Plasterboard, also called drywall, and veneer plastering are two main modern methods in USA and UK used in construction of the interior walls of modern homes . By attaching blue board over the frames of the house with screws, the plasterer usually shows up after the hangers have finished building all the internal walls, in case of traditional plastering. The plasterer is usually a subcontractor working in crews that average about three veterans and one laborer. To concentrate on plastering the "mud" onto the walls, the job of the laborer is to set up ahead of and clean up behind the plasterers.
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