Penetrating finishes surface treatments

Two basic types of finishes (or treatments) are used to protect wood surfaces during outdoor weathering those that form a film, layer, or coating on the wood surface, and those that penetrate the wood surface to leave no distinct layer or coating. Film-forming materials include paints of all description, varnishes, lacquers, and also overlays bonded to the wood surface. Penetrating finishes include preservatives, water repellents, pigmented semitransparent stains, and chemical treatments. 

Waterborne Salts. Waterborne inorganic salts are a special group of penetrating finishes. These surface treatments result in a finish similar to the semitransparent penetrating finishes because they change the color of the wood and leave a surface deposit of material similar to the pigment found in the semitransparent stains. 

Penetrating Finishes. Penetrating finishes, which do not form a film over the wood, include oils, water repellents, stains, preservatives, and surface treatments. 

The addition of 0.02% of an aqueous emulsion of silicone liquid into sand fibre slate reduces its water absorption by two and noticeably increases its cold resistance. Silicone liquids can be also put on finished constructions in the form of a 5% aqueous solution, which penetrates to the depth of 3-6 mm and after drying forms a durable waterproof surface for 5-10 years. This treatment can be used on various works of art, famous architectural buildings, etc. Plastered facades can also be waterproofed with good results. Treated plaster does not absorb rain drops on the other hand, common plaster completely absorbs all rain drops after 30 seconds. 

The oldest repellent finish is to repel water. The purpose of this finish is self evident. Drops of water should not spread on the surface of the textile and should not wet the fabric. The drops should stay on the surface and easily drip off. Similarly, oil repellent finishes should prevent oily fluids from wetting treated textiles. In a similar manner, soil-repellent finishes should protect textiles from both dry and wet soils. In all cases, the air permeability of the finished fabric should not be significantly reduced. Waterproofing treatments will not be covered in depth. A waterproof textile should withstand the hydrostatic pressure exerted by a column of water from at least aim height before the first drops of water penetrate through the fabric. In practice this is mostly achieved with coatings which have the disadvantages of stiff handle, lack of air and vapour permeability and consequently poor wear comfort. 

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