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Varnish on wood stairs Varnished oak floor. Varnish is a clear transparent hard protective coating or film. It is not to be confused with wood stain. It usually has a yellowish shade due to the manufacturing process and materials used, but it may also be pigmented as desired. It is sold commercially in various shades.
Chemical staining of wood is rarely carried out because it is easier to colour wood using dye or pigmented stain, however, ammonia fuming is a chemical staining method that is still occasionally used to darken woods such as oak that contain a lot of tannins. Staining of wood is difficult to control because some parts of the wood absorb more ...
A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol. [3] Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as alternating copolymers. Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule.
Wood stain is a type of paint used to colour wood comprising colourants dissolved and/or suspended in a vehicle or solvent. Pigments and/or dyes are largely used as colourants in most stains. The initial application of any paint or varnish is absorbed into the substrate similarly to stains, but the binder from a stain resides mainly below the ...
Without elasticity, the varnish would soon crack, allowing water to penetrate the wood beneath. Prior to the development of modern polymer chemistry, varnish production was rudimentary. Originally, spar varnish was a "long oil" varnish, composed primarily of drying oil with a small proportion of resin, usually boiled linseed oil and rosin. [1]
Alkyd resins are usually classed as long oil, [11] medium oil and short oil. [12] These terms represent the oil length in the resin. [ 13 ] Alkyds are also modified with phenolic resin , styrene , vinyl toluene , acrylic monomers (to make them dry more quickly) and isocyanates to produce a polyurethane modified alkyd.
Finishing the piece will require fine abrasive paper, always backed by a sanding block. Choices of sealers and finishes that can be applied include ordinary varnish, special varnishes, polyurethane (either oil or water based), wax, and French polish. Sand shading is a process used to make a picture appear to be more three-dimensional.
Moisture cured polyurethane–urea coatings have been made by reacting 1,2,3-triazole rich polyether polyols with HMDI at NCO/OH eq. ratio of 1.2 to obtain isocyanate-terminated polyurethane prepolymers. The prepolymers were cured under atmospheric moisture to make polyurethane–urea free films. [5]