Plasterwork is used to provide a smooth, flat surface to internal walls and ceilings. These smooth walls are suitable for decorating with paint or wall paper. Plastering also has the added advantage of offering sound and heat insulation, and it is fire-proof as well.
There are many plasters but they fall into two main types – gypsum based plasters and cement based plasters. Cement based plasters are used mainly for outdoors, generally for Gypsum based plasters are used indoors only – damp will attack a gypsum based plaster and cause it to crumble if used on exterior walls.
Cement based plasters can be used indoors for areas that are susceptible to damp and areas that require a greater thickness of cover.
The most common gypsum plasters are browning, bonding, and metal lathing plaster. Modern plasters come ready-mixed with perlite, vermiculite and several other additives. These additives provide a greater degree of insulation and fire resistance. Other ingredients slow down the setting time and generally make the mixture more workable.
Today the only additive we need to add is good clean water. When plastering materials with differing absorption, it is a good idea to key the surfaces to be plastered with a bonding sealer. This prevents the plaster ‘going off’ (setting) at different speeds.
Browning plaster (perlite) – brickwork, coke breeze, clay tile partitions, thermalite blocks, concrete bricks.
Bonding plaster (vermiculite) – concrete, stonework, cork slabs, surfaces treated with PVA.
Metal lathing plaster (perlite with vermiculite & rust inhibitor) – expanded metal lathing, wood wool slabs.
One Coat Plaster – used for any surface as undercoat and finish.
Alternative Plastering Option:
Fibrous plaster is a very beneficial method of choice when casting your decorative moldings.
Fibrous plaster is composed of plaster laid upon a backing of canvas stretched over a wood or steel frame. Fibrous plaster is used in casting circular and enriched moldings for columns, girders, and various types of ornamental work. It is usually worked in a shop and then attached to something else as a decoration by screws, hooks, or fixed in position by some other method. This type of molding saves time attributed to the delay of working on the ornamental projects on site and in position. This type of work is also used for temporary work, such as exhibition buildings.
A French modeler named Leonard Alexander Desachy first took out a patent in 1856 for “producing architectural moldings, ornaments and other works of art, with surfaces of plaster.” his method used materials such as plaster, glue, wood, wire, and canvas or other woven fabrics. Although the modern uses of this type of plastering technique can be said to have started then, it was widely used by people dating as far back as the Egyptians and probably predates even them. The Egyptians used it for decorating coffins and making masks, some of which are still preserved today, proving that when linen is stiffened with plaster, it can create very long-lasting products.
Fibrous plaster has many advantages over other choices. It is a lot lighter and improved reinforcement so moldings can be transported easier to the site where they are going to be installed. The use of modular cast moldings not only can make your finished products more uniform during installation, but also saves a lot of time and effort. For example, installing a pre-made figure into a space with specific dimensions for the figure saves in having to model each figure from scratch and installing them individually. Doing this costs less for the decorations themselves, and is alot more efficient for your builders, costing you less in their work as well.
Fibrous plaster is not only used in designing or decorating houses, but also in theatres, music halls, museums, and many other places where a grand effect is required. It allows those working with a limited budget and space to work in more choices and better products available to them. Theatres are renown for having access-ways that are built behind their facades, as well as lighting rigs that are cut through the ceilings. If this was done with solid plaster, or other material, their lavishly ornamented decorations would weigh so much it would require a massive structural support. This support would eliminate any workable space provided by the lighter materials.
In the past, fibrous plaster allowed the mass-production of extremely decorative moldings such as cornices and ceiling roses that were a major part of Victorian and Edwardian interior design.
Through time, we have learned that the biggest threat to these beautiful decorations is accidental damage, dampness of the environment the molding is in, and natural decay of the hessian backings of the molds. Expert advice should be sought in helping you preserve your castings in your home and buildings, so that they last al long as possible and are enjoyed by generations to come.
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