Varnish and lacquer

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In its most basic form varnish is made up of a binder that is naturally solid at room temperature, dissolved (or suspended) in a solvent. The binder is either resin, lacquer or cellulose. When applied to wood the solvent evaporates, leaving the binder on the surface.

Resin and lacquer

Resins and lacquers are solid (or semi-solid) amorphous substances exuded from certain trees, primarily the lacquer tree. Slower-drying natural lacquers contain oleoresins.

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Above Left to right: Liberon Danish oil; Liberon finishing oil; Sorby friction polish; Sorby Danish oil; boiled linseed oil; organ burnishing oil; organ finishing oil; Sorby universal lacquer; Sorby lemon oil; liquid paraffin.

Cellulose

Cellulose is carbohydrate, a starchy substance that forms the cell walls of plants. Cellulose derived from the cotton plant and treated with nitric and sulphuric acid makes nitrocellulose (cellulose nitrate), which is the primary resin material used in making cellulose lacquer. The soJvent used in cellulose lacquer is not compatible with other solvents. Cellulose-based lacquers arc harder and more chemical resistant than other resin-based lacquers.

Synthetic

Synthetic varnishes are usually organic: they have a polymeric structure produced by synthetically composing molecules. Modern technology has developed synthetic varnishes that have a very similar molecular structure to natural lacquer.

Acrylic

Acrylic varnishes are made up of synthetic resin suspended in water. It is the use of water that distinguishes acrylics from other varnishes because there is no use of volatile organic compounds (VOCs).

which are harmful to both the individual and the environment. Acrylics are faster drying than solvent-borne resins and are also generally tougher tlian solvent-dissolved resins.

Commercial products

Varnish and lacquer can be a mixture of resin and polymerizing oil in a solvent. The solvent evaporates with the resin and the oil polymerizes, leaving a hard and dry coating on the wood. The use of additives further improves its drying and wearing qualities.

Craftlac melamine is a cellulose-based finish. It contains melamine particles and toluene solvent, which produces a tough finish. Use cellulose thinners with this product.

Sanding sealers are varnishes (resin, cellulose or acrylic-based) with wood dust added. The purpose is to fill and seal the pores of wood with the wood particles, creating a clean, smooth surface when the surface varnish is sanded off. The wood dust is usually made from white wood so beware of using it on open-grained dark woods. Sanding sealers are usually used as preparation before another finish.

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