Glossary of Paints Terms

The Firwood A – Z of paint terms. Is a brief explanation of some technical terms use within the Paint Industry.

Acid Etch

Surface treatment using a diluted acid to etch the surface to provide a key for subsequent painting.


A synthetic resin used in high performance water based and solvent borne coatings.


The ability of dry paint to attach to and remain fixed on the surface without blistering, flaking, cracking or being removed by tape.

Air Cure

One method by which liquid coatings cure to a dry film. Oxygen from the air enters the film and cross-links the resin molecules. Also called "Air Dry" and "Oxidizing"


Synthetic resin modified with oil. Coating that contains alkyd resins in the binder.

Ambient Temperature

Background temperature. Relevant to the satisfactory film formation when painting and curing of the coating.


Solid ingredients in a coating that hold the pigment particles in suspension and attach them to the substrate. Consists of resins (e.g. oils, alkyd, latex). The nature and amount of binder determines many of the paints performance properties - toughness, adhesion, colour retention, etc.

BS Shades

British Standard colour systems used for the specification of paint colours.


Substance whose presence increases the rate of a chemical reaction, e.g. acid catalyst added to an epoxy resin system to accelerate drying time.

Cathodic Protection

A method used in the protection of metallic substrates from corrosion by using an electrical current or attachment of a sacrificial anode to the surface.


Formation of a powder on the surface of a paint film caused by disintegration of the binder during weathering. Can be affected by the choice of pigment or binder.

Chlorinated Rubber

A non-convertible coating produced from the polymerisation of rubber and chlorine blended with non-saponifiable plasticisers. Shows good resistance to acids and alkalis.

Clear Coating

A transparent protective and/or decorative film.

Coalescing Solvent

The small amount of solvent contained in emulsion paints to aid film formation.


A paint, varnish, lacquer or other finish used to create a protective and/or protective layer. Generally used to refer to paints and coatings applied in an industrial setting as part of the original equipment manufacturers (OEM) process.


A bonding together of a single substrate to itself. Internal adhesion.


Concentrated colour (dyes or pigments) that can be added to paints to make specific colours.


Non-fading in prolonged exposure to UV light.

Colour Retention

The ability of paint to keep its original colour. Major threats to colour retention are

exposure to ultraviolet radiation and abrasion by weather or repeated cleaning

Convertible Coating

Type of coating that undergoes a chemical change following or during application. May be a single or two pack. (See also non-convertible coating).

Corrosion Inhibitive

A type of metal paint or primer that prevents rust by preventing moisture from reaching the metal. Zinc phosphate for example is a common corrosion inhibitive pigment used in paints.

Cure, Curing

The process by which a liquid coating becomes a hard film.

Dew Point

The dew point is the temperature at which the water vapour in air condenses onto liquid water at the same rate at which it evaporates. At temperatures below the dew point, water will leave the air and create a damp surface. Always try and apply paints when the surface temperature of the object being painted is 6°C or more higher than the dew point.


Abbreviation for Dry Film Thickness, a measurement of the thickness of the paint film once the paint has completely cured.


A liquid used in coatings to reduce the consistency and make a coating flow more easily. The water in latex coatings is a diluent. A diluent may also be called a "Reducer", "Thinner", "Reducing Agent" or "Reducing Solvent".


Various compounds added to coatings to speed the drying.

Drying Oil

An oil that when exposed to air will dry to a solid through chemical reaction with air: linseed oil, tung oil, perilla, fish oil, soybean oil.

Earth Pigments

Those pigments that are obtained from the earth, including barytes, ochre, chalk and graphite.


Gloss level between semi-gloss and matt. Refer to gloss below.


A mixture of solids suspended in a liquid.

Emulsion Paint

Coating in which resins are suspended in water, then flow together with the aid of an emulsifier. e.g. latex paint.


Broad classification of paints that dry to a hard, usually gloss finish.


Extremely tough and durable synthetic resin used in some coatings. Epoxy coatings are extremely tough, durable and highly resistant to chemicals, abrasion, moisture and alcohol.


Ingredients added to paint to increase coverage, reduce cost, achieve durability, alter appearance, control rheology and influence other desirable properties. Less expensive than prime hiding pigments such as titanium dioxide. e.g. barium sulphate, calcium carbonate, clay, gypsum, silica, talc. May also improve coating performance.


Compounds containing predominantly iron.

Film Build

Amount of thickness produced in an application. Microns (mic) of dry film per microns of applied wet film.

Fire Resistance

The ability of a coating to withstand fire or protect the substrate to which it is applied from fire damage.

Forced Dry

Baking the paint between room temperature and 100ºC to speed the drying process.


Process in which a thin coating of zinc is applied to iron or steel to prevent rust.


The lustre or shininess of paints and coatings. Different types of gloss are frequently arbitrarily differentiated, such as sheen, distinctness of image gloss, etc. Trade practice recognises the following gloss levels;

Matt - practically free from sheen, even when viewed from oblique angles (usually less than 15% on 60º meter)

Eggshell - usually 20-35% on 60º meter

Semi-gloss - usually 35-70% on 60º meter

Full gloss - smooth and almost mirror-like surface when viewed from all angles, usually above 70% on 60º gloss meter.

Gloss Meter

A device for measuring the light reflectance of coatings.


Curing agent for epoxies and other two pack paints.


Restricting the passage of moisture, air or other substances.


A material that will not react chemically with other ingredients.


A mechanism whereby fire-retardant paints protect the substrates to which they are applied. An intumescent paint puffs up when exposed to high temperatures, forming an insulating, protective layer over the substrate.


Coatings held in store for long periods can jell. And should not be used without first testing their application.


An extender pigment used in paints and fillers that is a form of hydrated aluminium silicate.


The roughening of a surface to improve mechanical adhesion.


A hard area on a wood surface caused by the previous presence of a branch.Knots can be prone to sap bleeding and shrinkage over time.A very dense wood knot can lead to poor penetration during applications of coatings.


A fast-drying usually clear coating that is highly flammable and dries by solvent evaporation only. Can be reconstituted after drying by adding solvent.

Historical Note: The word lacquer is derived from the word lac, which describes the secretions of the lac beetle. This insect, found mainly in Asia, deposits its secretions on branches of trees and this crop is later harvested. The resin developed by the insects, in its original state, contains a red dye. This dye is separated from the resin by boiling in water. Next the residue resin, known as seed lac, is melted, strained, cooled and flaked and then becomes shellac.


A white milky powder material found on the surface of newly laid concrete.


A flat, thin, plate-like particle.Aluminium and flakes and mica are examples of lamellar shaped pigments.


The overlapping orientation of lamellar pigment in plane horizontals to the surface plane .Leafing aluminium, mica and micaceous iron oxide are typical.

Linseed Oil

Drying oil made from the flax seed. Used as a solvent in many oil based paints. "Boiled" linseed oil can be used to protect wood from water damage. Sometimes used as a furniture polish.

Liquid Driers

Solution of soluble driers in organic solvents.

Marine Paint

Coating specially designed for immersion in water and exposure to marine atmosphere. (See also Anti-fouling Paint)

Material Safety Data Sheet (MSDS)

Information sheet that lists hazardous substance in a product. Also lists procedures to follow in the event of fire, explosion, leak or exposure to hazardous substance by inhalation, ingestion or contact with skin or eyes. Coatings manufacturers are required to provide trade customers with an MSDS for every hazardous product they sell.


A surface that scatters or absorbs the light falling on it so as to be substantially free from gloss or sheen (0-15% gloss on a 60º gloss meter).


Aluminium potassium silicate.A non-opaque pigment principally obtained from the mineral Muscovite. The particle shape of mica is lamellar (plate-like) and is used extensively for film reinforcement to reduce permeability and improve cracking and checking resistance as well as being cosmetically attractive.

Moisture Repellent

A coating that sheds moisture from the surface.

Moisture Resistant

Allows a coating to resist swelling, blistering and other damages caused by moisture.


Substance composed of low molecular weight molecules capable of reacting with like or unlike molecules to form a polymer.


A petroleum distillate used mostly by professionals (as opposed to DIY painters) for clean-up and to thin solvent based coatings. A volatile organic compound (see VOC).

Natural Finish

Generally a term used for wood, meaning to give the appearance of no coating being applied. A penetrating stain is used to achieve this effect.

Non-Convertible Coating

Also known as a thermoplastic. These coatings form films by the simple physical process of the evaporation of solvent.


A material containing no iron. Describes substrates such as aluminium, copper etc.


A paint or coating that contains an aggregate or an aggregate has been added to during the application.


A substance that is not poisonous.


The portion of a coating left after the solvent evaporates; sometimes called the solids content.

Odourless Solvent

A low strength hydrocarbon solvent. Has a low odour that mildly smells like paraffin.

Oil Paint

A paint that contains drying oil, oil varnish or oil-modified resin as the film forming ingredient. The term is commonly and incorrectly used to refer to any paint soluble by organic solvents.


The covering power. The capacity to obliterate the colour of the surface to which it is applied. It indicates the relative ability of the coating to reflect or absorb light rather than transmit light and is thus the inverse of transparency.

Over Painting

Covering one colour or substance with another.


Chemical reaction upon exposure to oxygen. Some coatings cure by oxidation, when oxygen enters the liquid coating and cross-links the resin molecules. This film forming method is also called "Air Cure" and "Air Dry". (Oxidation also causes rust on bare metals).


A coating including resin, a solvent, additives, pigments and, in some products, a diluent.

Paint Remover

A chemical that softens old paint or varnish allowing it to be easily scraped off. Also called "stripper".

Paint System

A succession of selected coats of materials applied in a prescribed order to protect a surface and provide a protective surface.

Paint Thinner

Cleaning solvent or diluent used to reduce the viscosity of paints.


A colour specification system widely used within the ink industry.


The ability if a surface or coating to allow the passage of gas, vapour or liquid.


Insoluble, finely ground materials that give paint its properties of colour and opacity. Titanium dioxide is the most important pigment used to provide opacity in paint. Other pigments include anatase titanium, barium metaborate, barium sulphate, burnt sienna, burnt umber, carbon black, china clay, chromium oxide, iron oxide, Tuscan red, zinc oxide, and zinc phosphate.


A substance, the molecules of which consist of one or more structural units repeated any number of times, vinyl resins are examples of true polymers.


The interlocking of molecules by chemical reaction to produce very large molecules. The process of making plastics and plastic based resins.

Polyvinyl Chloride

A synthetic resin used in the binders of coatings. Tends to discolour under exposure to ultraviolet radiation. Commonly called "vinyl".

Pot Life

The workable life of a two paint once mixed. Paint should not be used after their pot life expires. Pot life will be reduced at higher temperatures.


First complete coat of paint of a painting system applied to a surface. Such paints are designed to provide adequate adhesion to new surfaces or are formulated to meet the special requirements of the surfaces.


The gas used to expel materials from aerosol containers.

Quality Assurance

The verification of the conformance of materials and methods of application to the governing specification in order to achieve the desired result.

Quality Control

Ensuring materials and final product meet a given standard.

Quick Drying

Term generally for a coat that dries or cures in short period of time.


A colour matching system developed in Germany and used extensively across Europe for the specification of colours by architects and engineers.


Thinning or adding a solvent to a coating to reduce viscosity or solid content.


Synthetic or natural material used as a binder in coatings. Can be translucent or transparent, solid or semi-solid. Examples; acrylic, alkyd, epoxy, polyurethane, polyvinyl chloride, silicone.


Washing a substrate with a liquid to remove residues or contaminants.


Natural resin obtained from living pine trees or from dead tree stumps and knots.


The corrosion of ferrous metals resulting in the formation of oxides on the surface that appear as yellow to dark reddish brown.

Salt Spray Test

A method used to determine the relative resistance to corrosion of coatings on metal substrates using a constant spray of a synthetic saltwater solution in a controlled environment.

Sand Finish

Rough finish plaster or stucco, or an paint applied that has been texturized with sand.


Abrasive cleaning technique.


Abrading a painted or bare surface with an abrasive coated material by machine or hand, to smooth or remove surface defects of to improve the mechanical adhesion of a coating.

Satin Finish

A dried film that does not have full luster but resembles satin.

Semi-Gloss Finish

Finish that has a low lustre sheen. Semi-gloss paints are formulated to give this result (usually 35-70% on a 60º meter).

Shelf Life

The time span that a material should be stored in its original and unopened container before physical or chemical changes begin to take place that could make the contents unusable.


A coating made from purified lac dissolved in alcohol, often bleached white.

Shot Blasting

The preparation and cleaning of substrates by shooting metal shots at the surface to remove contaminants.


A resin used in the binders of coatings. Also used as an additive to provide specific properties, e.g. de-foamer. Paints containing silicone are very slick and resist dirt and graffiti. Also very stable in high heat.


The formation of a dry or semi-dry layer of paint or resin on the surface of the paint or varnish in a partially filled container or that has been exposed to the air for some time.


The part of the coating that remains on a surface after the vehicle has evaporated. The dried paint film. Also called non-volatile.

Solids By Volume

The total volume percentage of non-volatile material. Also known as volume solids. The solids by volume is used to calculate the dry film thickness (DFT) of coating from wet film measurements taken during application.

Solids By Weight

The percentage of the total weight of a coating occupied by non-volatile compounds.


Any liquid which can dissolve a resin. Generally refers to the liquid portion of paints and coatings that evaporates as the coating dries.

Solvent Based Paints

To describe paints and coatings that use any organic solvents as the primary volatile thinner.

Spatter Finish

A speckled or raised texture finish.

Spot Priming

The protection of localised spots. Spot primed areas are those that required additional protection due to rusting or peeling of the former coat. May also be required after a substrate requiring a primer/sealer has been repaired.


Any surface to which a coating is applied.


Substance of Very High Concern. When first identified, under REACH legislation these are added to a candidate list. Firwood seek to ensure that none of the chemicals used in their products are SVHC.

Thinning Ratio

The recommended proportion of thinner to be added to a coating material to make it suitable for a particular method of application.


A colour produced by mixing white pigment or paint with a non-white coloured pigment or paint.

Titanium Dioxide

White pigment in virtually all white paints. Prime hiding pigment in most paints.


Distilled pine oil, used as a cleaner, solvent or thinner for oil based and alkyd coatings.

Two Pack Paint

A coating material supplied in two parts that have to be mixed in the directed proportions before use. The mixture is only usable for a limited time. (See Pot Life).


An important resin in the coatings industry. A true urethane coating is a two component product that cures when an isocyanate (the catalyst) prompts a chemical reaction that unites the components.


The coat or coats applied to a surface after priming, filling etc. or after the preparation of a previously painted surface and before the application of the final coat.

Vacuum Blasting

Abrasive blast cleaning method using specialist equipment that recovers the abrasive.


Portion of a coating that includes all liquids and the binder. The vehicle and the pigment are the two basic components of paint.


See Polyvinyl Chloride


The property of a fluid whereby it tends to resist relative motion within itself.


See Volatile Organic Compound


The defining quality of a liquid that evaporates quickly when exposed to air.

Volatile Organic Compound

Organic chemicals and petrochemicals that emit vapours while evaporating. In paints, VOC generally refers to the solvent portion of the paint which, when it evaporates, results in the formation of paint film on the substrate to which it was applied. The VOC content in paints is restricted by legislation so as to reduce their environmental impact.

Volume Solids

Solid ingredients as a percentage of the total ingredients. The volume of pigment plus binder divided by the total volume, expressed as a percent. High volume solids mean a thicker dry film with improve durability.

Water Borne

Coatings in which the majority of the liquid content is water.

Water Immersion

When coatings are exposed and directly in contact with water.


Abbreviation for Wet Film Thickness.


A petroleum distillate used as a solvent and cleaner for alkyd and other resins, it evaporates more quickly than white spirit and is therefore used for spraying, rather than brushing applications.


Development of a yellow colour in paints, lacquers or varnishes. Oil and oil/alkyd based coatings may yellow over time.

Zinc Phosphate Primer

A paint or coating containing zinc phosphate pigment. Apply to steel to inhibit corrosion.

Zinc Rich Primer

An anti-corrosive primer for iron and steel. Zinc dust is incorporated in a concentrated form sufficient to give electrical conductivity in the dried film, allowing the zinc metal to corrode preferentially to the substrate providing cathodic protection.

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