SURFACE
The surface is the material to which the sealant is applied or the exposed side of the material to be glued (adhesive). It is a major factor in product selection. To choose the right product, you must consider the type and condition of surface to be sealed or glued. There are five types of surfaces: gypsum (gyproc), wood, masonry, metal and synthetic material. Surfaces may be bare or already painted, in good or poor condition and dirty or clean. The main characteristics and types of surface deterioration are described below.
Gypsum
Nowadays, Gypsum is the material most commonly used in the construction of interior ceilings and walls. It is in fact a sheet of plaster covered with layers of paper on both sides. It usually comes with a standard paper, but it is also available in water-resistant and fire-resistant varieties. Gypsum is porous, has a poor ability to withstand shocks and is easily perforated. It is sensitive to expansion and contraction movements caused by house shifting or settling and by temperature fluctuations. Some water-based elastomer sealants, such as the acrylic latex sealant & crack-filler, can be used for minor repairs.
Wood
There are two major types of woods: softwoods (conifers) and hardwoods (deciduous trees). Of the hundreds of different kinds of wood we know, only a few are used in construction. The most commonly used softwoods are cedar, pine, fir, redwood and spruce. The most commonly used hardwoods are oak, ash, walnut, beech, elm, cherry, mahogany, maple, rosewood, birch, linden and teak.
Wood expands not only with temperature fluctuations but with humidity changes. Also, some species like red cedar and redwood contain natural water-soluble colorants that can give pale water-based paints a brownish cast.
Some wood-derived products are used to build sub-floors. They are known as plywood (which consists of glued thin sheets of wood) and wood particle boards (which consists of wood chips glued together with a water-resistant boiling-proof binder). You can apply water- and solvent-based adhesives on plywood. On the other hand, you must only apply solvent-based adhesives on wood particle boards, since they contain a high percentage of binder which keeps the particles glued together. The type of binder can considerably vary from one batch of boards to another and the use of water-based adhesives on those boards lead to extremely variable results.
Masonry
Masonry includes concrete, stone, brick, plaster and stucco. The main types of surface deterioration are cracking, crumbling and efflorescence (brick, concrete, plaster). Efflorescence is a white powder that forms on the surface of masonry materials as a result of excess humidity. Humidity dissolves mineral salts contained in the masonry and transports them to the surface where they build up as water evaporates.
Because it’s very porous, masonry contains a higher percentage of humidity than other surfaces. This humidity can keep sealants or adhesives from adhering properly. Also, concrete contains alkalis which can reduce the adhesive power of chemical and water-based sealants and of water-based adhesives by chemically reacting with some of their ingredients.
Metal
Metal is a hard, tough and heat-resistant material. There are four types of metal: ferrous (cast-iron, wrought iron and steel), nonferrous (copper, aluminum, nickel and zinc), precious (gold, silver and platinum) and alloys. The latter are metal products formed by incorporating one or more elements into a metal to produce substances like brass or bronze. Brass is an alloy formed from copper and zinc, while bronze is formed from copper and tin.
Metals deteriorate mainly through corrosion. Ferrous metals, other than stainless steel, can easily oxidize in moist air by creating rust. They must be protected before a sealant or adhesive is applied. Nonferrous metals, precious metals and alloys resist very well to corrosion. Because they are impermeable, it is difficult to use glue on metals and adhesives dry more slowly.
Synthetic surfaces
There are two major types of synthetic surfaces. One is mineral based, like glass and ceramics, and the other is formed from petroleum derivatives, like tar and plastics. Glass is essentially made from melted silicate (sand). It retains heat and light passes through it. Ceramics are made from baked clay. It is attractive, tough and easy to maintain.
Plastics are resistant, tough, long-lasting materials. They are economical, resist corrosion, and absorb shocks and vibrations. Many kinds of plastics are available, including polyvinyl chloride (PVC), nylon, polyester, epoxy, alkyd polyester, polyethylene, urethane, silicone, laminates, polystyrene, etc.
It is sometimes impossible to use some solvent-based adhesives or sealants on certain plastics because they dissolve in a number of solvents.