Specialist wood finishing terms in plain language

Over the years we have provided information on wood finishing, the materials and technologies used, problems that can occur and finishing defects. I have often used specific technical terms, due to the experience gained in years of working with finishing materials, without thinking that they are not common words or that some have a different meaning in finishing than the unanimously accepted one. They are terms you often find on the labels of waxes, oils, varnishes and paints in the shops. For those in the position of novice wood enthusiasts who want to use this information in their projects, the terms can create confusion and give rise to questions ( Does primer stain? Can I varnish? What is the difference between varnish and paint?). I propose to briefly explain these terms below, including references to magazine articles where you can find the product or operation described in detail. To make it easier to follow, the terms have been arranged in alphabetical order.

Antiquing 

A series of operations leading to an object or furniture with an antique appearance. Antiquing uses both techniques that are applied to wood to make it resemble naturally aged wood (knocking, scratching, staining) and materials that give it the patina of age. There are various antiquing technologies and you will find some of them in dedicated article this operation.

Baiț

Staining solution which is used to colour the wood so that the natural lion design is visible. It is a transparent way of staining the wood, while the grain remains visible. The term ink, borrowed from Italian.

Orange peel

The veiny appearance of the varnish or primer film, similar to orange peel. This is a finishing defect that can occur for various reasons: the material applied is too thick (insufficient dilution), the pressure of the compressed air in the gun is too high, the temperature of the varnish and the wood are at different temperatures during application. In order for the film to be re-stretched, this layer must be removed by sanding and another layer applied. More information about orange peel here.

Corp solid

A term used to denote the solid resin content of a varnish, paint or other finishing product. These products are still diluted with water or organic solvents at the time of manufacture. After application the water and solvents evaporate and the solid resin remains on the wood. This term, which can be found in the data sheet or on the product label, indicates how much material will remain on the wood as a film (the resin) and how much will evaporate (the water or thinner). The solids content is expressed in percentages and is one of the terms that indicate the quality of a finishing product. A higher solids content means a better product.

VOCs Volatile organic compounds

The total amount of organic solvents in varnish, primer or paint that evaporates and reaches the working environment or the atmosphere through exhaust systems. It is expressed as a percentage and is always stated on the label. About volatile organic compounds and their influence on the environment you can find information on here.

Viscometric cup

Instrument for measuring the viscosity of varnishes, paints or primers. Viscosity indicates the time, in seconds, that a quantity of material comes out of the orifice (nozzle) of a cup. Viscosity is an indicator that can be found in the product data sheet and can be easily checked (unlike solid body which is much more difficult to determine). The cup is also used to check the application viscosity of these products after mixing them with the recommended solvent. The application viscosity is a parameter recommended by the manufacturer and can be found in the technical data sheet or on the product label. It is one of the parameters that helps us to avoid the appearance of orange peel.

Dispersion

Mixture in equilibrium between a liquid component and fine particles of solid material. For example, PVA adhesives (polyvinyl acetate), of the aracite type, are aqueous dispersions.

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Opaque pigmented paint/varnish through which the natural wood grain cannot be seen. The enamel is not transparent.

Glaze

Material for staining and patinating wood. Glazes come in many types and are usually used to give an antique look to wood or to achieve special effects on wood.

Gloss

Gloss = Degree of gloss. Shows the ability of the film to reflect light. The film, whether transparent or opaque, can be glossy or matt depending on how much it reflects light. The amount of light reflected can be measured and the result is expressed in numbers from 0 to 100, where 0 means a very matt film with no gloss and 100 means a very glossy film. There are varnishes and paints with varying degrees of gloss. An object can be lacquered even if it has no gloss. Lack of gloss does not mean that the varnish is missing. There are varnishes with a gloss level below 5 that have no sheen and protect the wood without affecting its natural appearance.

Grund

A topcoat with very good coating, adhesion and sanding properties, applied directly to stained or unstained wood. It is the substrate on which the final varnish coat is applied. A system containing primer and varnish/paint allows a superior film quality to be achieved. This is how wood finishing is done in factories. In DIY projects it is not always mandatory to use it.

Hardener/Catalyst

Component B of two-component varnishes/coats/paints. Following the reaction between component A (primer/varnish/paint) and catalyst the film forms.

Steel wool

Very fine abrasive material that is actually a very fine steel wool-look dart-pulled bit. It is used for fine sanding to create various special effects. For example it is used to remove wood-aging skids so that they remain only in certain places. Being very fine it removes skids without scratching the varnish or paint layer.

Lake

Transparent finishing material, applied as a final finishing coat. Like paint (enamel) it gives surface properties to the film: pleasant tint, mechanical and chemical resistance, gloss.

Metamerism

The apparent change in the hue of a colour depending on the source of light, natural or artificial, given by a light bulb or neon lamp.

Over-spray

The amount of material resulting from spraying that does not settle on the object and remains in the working environment. This material is lost and a gun or spray application system is more efficient the smaller the amount.

Patina

Finishing material used to create various effects on wood or furniture: antiquing, wood pore marking, slight gold or silver accents, etc.

Pot-life

As you saw above there are two-component finishing materials. The time during which the mixture can be used without the reaction between the two starting, thus changing its properties, is called pot-life or pot life. After this time the mixture changes its properties and starts to be thicker, less fluid. At this stage it can no longer be used even if it is diluted to reach its original viscosity.

Shellac

Natural orange resin secreted by a species of insects from India and Indochina. Dissolved in organic solvent it forms the lake of the same name. In the following links you will find extensive information on both the lake itself as well as about frech polish, the application method so as to achieve glossy surfaces with a particularly silky appearance.

Thixotropy

The property of some film-forming materials to have low viscosity under stirring and high viscosity at rest. Varnishes with this property are easily applied vertically without the risk of material leakage. The appearance is that of a very thick varnish without necessarily having a large solid body. The viscosity of these varnishes cannot be determined with the viscometer cup. An example of such varnishes are the water-based ones for outdoor use.

I hope these explanations will help. If you have friends who have "stumbled" over such terms please help them by sharing the article. If you have any additions or questions leave them in the comments area.