About Wood Finishes

Use Cases and Properties

Reactive Finishes

Oil-Based Polyurethane-is a reactive (oxidizing) finish that will provide excellent protection and should be used only on interior surfaces. Oil-based polyurethane will color-shift over time and can turn lighter colored woods like maple, oak and birch a yellow color that may not be desirable. The film hardness of polyurethane tends to be lower than that of other finishes (lacquer, shellac, etc) which is good for crack resistance but bad for polishing.

 

Oil-Based Spar Varnish-is a reactive (oxidizing) finish that provides good protection for exterior woodwork. These finishes are very similar to their oil-based polyurethane cousins, but there are a couple of key differences. The first is that a spar varnish has an even lower film hardness than polyurethane and will resist cracking due to the substrate expanding and contracting with temperature changes. The second difference usually takes the form of a greater oil content in the varnish. The higher oil content aids penetration of the substrate and again reduces the final hardness of the film.

 

Tung Oil-is a reactive (oxidizing) finish that provides good protection for exterior woodwork. These finishes are very similar to their oil-based polyurethane cousins, but there are a couple of key differences. The first is that a spar varnish has an even lower film hardness than polyurethane and will resist cracking due to the substrate expanding and contracting with temperature changes. The second difference usually takes the form of a greater oil content in the varnish. The higher oil content aids penetration of the substrate and again reduces the final hardness of the film.

 

Boiled Linseed Oil-is a reactive (oxidizing) finish that provides good protection for exterior woodwork. These finishes are very similar to their oil-based polyurethane cousins, but there are a couple of key differences. The first is that a spar varnish has an even lower film hardness than polyurethane and will resist cracking due to the substrate expanding and contracting with temperature changes. The second difference usually takes the form of a greater oil content in the varnish. The higher oil content aids penetration of the substrate and again reduces the final hardness of the film.

 

Danish Oil-is a reactive (oxidizing) finish that provides good protection for exterior woodwork. These finishes are very similar to their oil-based polyurethane cousins, but there are a couple of key differences. The first is that a spar varnish has an even lower film hardness than polyurethane and will resist cracking due to the substrate expanding and contracting with temperature changes. The second difference usually takes the form of a greater oil content in the varnish. The higher oil content aids penetration of the substrate and again reduces the final hardness of the film.

Evaporative Finishes

Nitrocellulose Lacquer-is an evaporative finish that serves as an industry standard for interior wood finishing. Lacquer imparts a pleasing amber tone to the substrate it is applied to and resists yellowing as much as an oil based polyurethane does. The quick dry time, good sanding properties and easy repair of lacquer make it a great choice for signs and trays and most other interior-only items. The primary downfall of lacquer is its poor protection from water.

 

Shellac-is another evaporative finish that consists of natural resins dissolved in denatured alcohol. Shellac is a beautiful finish if applied well but should really be considered a cosmetic finish due to its lack of resistance to a variety of solvents, cleaners etc.

Water-based Finishes

Acrylic Lacquer-acrylic lacquers should not be confused with their nitrocellulose counterparts. This finish is essentially a dispersion of acrylic particles suspended in a mixture of water and some form of glycol ether. When the finish is applied, the water will evaporate causing the remaining dispersion to dissolve the acrylic particles and form a uniform surface film. These finishes dry quickly, sand well and will not color shift over time.

 

Polycarbonate Urethane-acrylic lacquers should not be confused with their nitrocellulose counterparts. This finish is essentially a dispersion of acrylic particles suspended in a mixture of water and some form of glycol ether. When the finish is applied, the water will evaporate causing the remaining dispersion to dissolve the acrylic particles and form a uniform surface film. These finishes dry quickly, sand well and will not color shift over time.

 

 

 

 

 

 

 

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