Glossary of Terms



Acrylic Acid

CH2=CHCOOH. Propenoic acid, vinylformic acid. A monomer used in the manufacture of coatings and plastics.

Properties: mol wt, 72.06; lmp, 14°C; bp, 41.0°C; sp gr, 1.422.

Acrylic Ester

Ester of acrylic acid, or of a structural derivative of acrylic acid, such as methacrylic acid.

Acrylic Latex

Aqueous dispersion, thermoplastic or thermosetting, of polymers or copolymers of acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile.

Acrylic Plastics

Thermoplastic or thermosetting plastics of polymers or copolymers of acrylic acid, methacrylic acid, esters of these acids, acrylonitrile.


Resins resulting from the polymerization of derivatives of acrylic acids, including esters of acrylic acid, methacrylic acid, acrylonitrile, and their copolymers. Syns: acrylic resins and acrylate resins.

Alkali Resistance

1. The degree to which a coating resists reaction with alkaline materials such as lime, cement, plaster, soap, etc. On weathering over alkaline cementitious substrates, latex paints can result in premature film failure (cracking, checking, chalking). This is most often due to the degradation of the binder (such as polyvinyl acetate) by alkaline salts normally present in the substrate causing hydrolysis, efflorescence, and/or mottling.

2. The degree to which a coating will resist attack by aqueous alkaline solutions.

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1. The diffusion of colorants through a coating from a previously painted substrate due to the action of the vehicle or solvent or both. The action is dependent on the pigments, vehicles, and solvents of the systems.

2. Diffusion of a soluble colored substance from, into, and through a coating from beneath, thus producing an undesirable staining or discoloration. Materials, which give rise to this effect, are tannins or dyes in some types of wood, wood preservatives, bituminous coatings, pigment dyestuffs, and stains.

3. Diffusion of coloring matter from the substrate; also, the discoloration arising from such diffusion. In the case of printing ink, the spreading or running of a pigment color by the action of a solvent such as water or alcohol (ASTM).

4. Migration to the rubber surface of an oil, wax, or plasticizer as a film or in drops, sometimes called sweating. Also a term applied to organic pigment colors if they migrate into an adjacent stock of a different color, or when they are removable at the surface by water or other solvent.

5. The spreading or migration of an ink component into an unwanted area.

Bleeding Knots

Usually circular-shaped discoloration in stained or painted siding.

Blister Resistance

The ability of a coating to resist the formation of dome-shaped, liquid or gas-filled projections in its film resulting from local loss of adhesion and lifting of the film from the underlying surface or coating. See blistering.

Blistering of exterior paints applied to wood siding is often due to high humidity within a structure. A driving force that causes blistering is humidity originating behind the substrate. There are various tests that simulate this particular situation. ASTM Test Method D 1735 uses a water fog apparatus similar to that used for salt spray testing. Test Method D 4585 uses controlled condensation. ASTM Test Method D 714 contains photographic standards for the degree of blistering size and frequency. The FSCT Pictoral Standards of Coatings Defects also has these same photographic standards.


Formation of dome-shaped hollow projections in paints of varnish films resulting from local loss of adhesion and lifting of the film from the underlying surface. (BSI) See blister resistance.

A phenomenon peculiar to painted surfaces is the formation of blisters relative to some system weakness. ASTM Test Method D 714 employs photographic reference standards to evaluate the degree of blistering. The FSCT Pictorial Standards of Coatings Defects contains the same photographic reference standards. ASTM test methods for blistering (blister resistance) include pictorial standards/evaluation (D 714); water condensation test (D 4585); water fog test (D 1735).

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Of or relating to the manufacture of any product (as earthenware, porcelain, or brick) made essentially from a nonmetallic mineral (as clay) by firing at a high temperature.


1.Formation of a friable powder (pigment rich) on the surface of a paint film caused by the disintegration of the binding medium due to disruptive factors during weathering. The chalking of a paint film can be considerably affected by the choice and concentration of the pigment. (BSI) It can also be affected by the choice of the binding medium.

2. A condition of a printing ink in which the pigment is not properly bound to the paper and can be easily rubbed off as a powder. (3) Formation of a powdery surface condition due to oxidation of the surface of rubber and release of pigments and fillers at the surface. Not to be confused with bloom, which looks similar.

The FSCT Pictorial Standards of Coating Defects contains photographic standards for the degree of chalking of exterior paints. ASTM Test Method D 4214 also has these same photographic standards as well as a second set of photographic standards.

Chalking Resistance

The ability of a coating to resist the formation of a friable powder on the surface of its film caused by the disintegration of the binding medium due to degradative weather factors.

The chalking of a coating can be considerably affected by the choice and concentration of pigment and binding medium.


That phenomenon manifested in paint films by slight breaks in the film that do not penetrate to the underlying surface. (ASTM) See checking resistance.

The break should be called a crack if the underlying surface is visible. Where precision is necessary in evaluating a paint film, checking may be described as visible (as seen with the naked eye) or as microscopic (as observed under a magnification of 10 diameters).

Checking Resistance

The ability of a coating to resist slight breaks in its film that do not penetrate to the underlying surface.

The breaks should be called cracks if penetration extends through the underlying surface. See cracking resistance. Where precision is necessary in evaluating a coating film, checking may be described as visible (as seen by the naked eye) or as microscopic (as observed under minimum magnification of 10 diameters). The FSCT Pictorial Standards of Coating Defects contains photographic standards for the degree of checking of exterior paints. ASTM Test Method D 660 has a different set of illustrated reference standards.


The deterioration of metal or of concrete by chemical or electrochemical reaction resulting from exposure to weathering, moisture, chemicals, or other agents in the environment in which it is placed. (DAC)

Critical Pigment Volume Concentration

(CPVC) That level of pigmentation, PVC value in the dry paint, where just sufficient binder is present to fill the voids between the pigment particles.

At this level, a sharp break occurs in film properties such as scrub resistance, hiding, corrosion resistance, ease of stain removal, etc. Different requirements for each product would dictate different PVC or CPVC ratios. Ceiling paints, for instance, are not required to be very washable and can be formulated at or above CPVC, whereas gloss paints and many exterior formulations are designed well below their CPVC, where CPVC has no significance. CPVC has significance only in flat paints.

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Chemical breakdown of a substance into two or more simpler substances which differ from each other and from the original substance. See degradation.


Change in characteristics or quality of the original substance through chemical breakdown or physical wear. See decomposition.

Degree of Efflorescence

1. Flatting and glossing - a nonuniform decrease or increase in gloss noticed when the surface is illuminated and viewed at near grazing angles. There is no apparent chance in color when viewed perpendicular to the surface.

2. Fine efflorescence - a barely discernible whitening of the surface when viewed perpendicularly. (3) Medium efflorescence - a readily noticeable whitening of the surface without a marked masking of the color. (4) Heavy efflorescence - a white deposit sufficient to mask the color. (ASTM)

Dirt Collection

The deposit of foreign matter consisting of dirt, soot, or stain present on the surface of exposed exterior coated panels. (ASTM) Syn: dirt pick-up

Exterior coatings often experience the accumulation of dirt not entirely removable from the paint film and result in change of color or appearance. Generally, harder and/or more hydrophobic films are more resistant to dirt collection. ASTM Test Method D 3719 quantifies dirt collection on coated exterior panels. This test method measures total dirt collection. Loose dirt may be washed and removed from the specimens if only imbedded dirt collection is to be measured.

Dirt Pick-up See dirt collection. Dirt/Soil Resistance

The ability of a coating to resist soiling by foreign material, other than micro-organisms, deposited on or embedded in the dried coating.

Dry Hiding

The increment of increasing scattering due to the larger difference in refractive index between air and pigment vs. pigment vs. binder and pigment.

It is the increase in the hiding power of a paint that occurs in the drying process. It is most significant in nonglossy paints, which, after drying, have pigments or extenders protruding from the surface of the paint film, which scatter the incident light, adding to hiding.

Hiding of paints changes during the drying process for two principal reasons. Initially, as the water and solvents leave the film, the pigment particles become more concentrated (crowded), thus lowering the hiding. Once the paint has dried enough that all the binder and pigment particles are packed together, air replaces the remaining water as it evaporates. Since the refractive index of air (1.0) is lower than that of water (1.3), hiding increases with the development of the air voids.

The drying hiding contribution to scattering can be estimated from Sdry - Swet, the scattering value for the dry films minus the scattering value for the films after brushing with high boiling aliphatic solvent which replaces the air and eliminates dry hiding. Above CPVC, paints have a large component of dry hiding; below CPVC, paints do not. In addition, Swet values are sometimes used as an indicator of the hiding of wet paints when they are first applied to the substrate.

Many architectural paints, particularly white and light tints, change significantly in film opacity as they dry. An increase in hiding is sometimes associated with porosity and poor film integrity with conventionally formulated coatings.

ASTM Test Method D 5007 covers the determination of the change in hiding of white and tinted architectural coatings during drying, by visual evaluation of the wet and dry film. ASTM Test Method D 2805 covers the determination of hiding power by reflectometry.

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1. The opposite of deliquescence. The drying of a salt solution when the vapor pressure of water in the saturated solution of a substrate is greater than the partial pressure of water in ambient air. Also refers to the loss of water of crystallization from a solid salt such as Na2CO3.1OH2O. (IUPAC)

2. For interior wall paints, a condition that occurs when soluble salts in the dried paint film or in the substrate migrate to the film surface during exposure. (ASTM). It should not be confused with other causes of nonuniform appearance or whitening that may occur at the time of application. Efflorescence is seen as either a light, medium, or heavy deposit of crystals. It exists both in isolated patches and over wide areas. ASTM Test Method D 1736 can beused for this problem. Some studies have shown that efflorescence of interior paints is due to excessive sodium salts in the paint formulation and that this can be overcome by replacing the sodium salts with potassium salts or overwhelming existing sodium salts with three times the amount of potassium salts. (ASTM)

3. For exterior paints, an incrustation of soluble salts, commonly white, deposited on the surface of coatings, stone, brick, plaster, or mortar, usually caused by salts or free alkalies leached from mortar or adjacent concrete as moisture moves through it. Efflorescence can affect the gloss and/or whiten the coating. Water-based coatings are most susceptible to this film defect. Since efflorescence results in the formation of white deposits on the film surface, it is more readily observed in tinted coatings, especially deep tones. ASTM Test Method D 1848 covers descriptions of properties that may be observed in weathered latex paint films. Efflorescence is included. The others are mottling (or blotching), water spotting, crawling, pinholing, and mudcracking. Efflorescence cannot be readily removed by wiping or with water only but can be removed with dilute mineral acid. ASTM Test Method D 1848 can be used for this problem.


Property by which a material tends to recover its original size and shape immediately after removal of the force causing deformation.


A natural or synthetic polymer which, at room temperature, can be stretched repeatedly to at least twice its original length and which after removal of the tensile load will immediately and forcibly return to approximately its original length. (ASTM)


Rubber like; relating to or having the properties of elastomers.


The increase in specimen length from the point of initial load application to the point of film rupture in a tension test. (ASTM)

Elongation measurements are of value in studying the behavior of coatings subjected to environmental stresses, such as those produced by aging and weathering. They may vary with specimen thickness, method of preparation, gage length, rate of load application, tensile tester response, and types of grips used. ASTM Test Method D 2370 covers the measurement of elongation as well as tensile strength and stiffness (modulus of elasticity) of organic coatings when tested as free films.


The relative power of a surface to emit heat by radiation; the ratio of the radiant energy emitted by a surface to that emitted by a blackbody at the same temperature.


The energy radiated by the surface of a body per second per unit area.

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Film Thickness

Thickness of any applied coating, wet or dry.

The thickness of the dried or cured coating on the substrate varies with the method of application and the rheology of the coating. Coating thickness on metal generally ranges from 0.5 to 4 mils. Wet film thickness measurements aid in the prediction of dry film thickness. In instances where dry film thickness cannot be measured nondestructively, wet film thickness is frequently specified. Also, the ability to determine wet film thickness during application can provide the opportunity to collect the application procedures. ASTM D 4414 is a practice describing the use of thin rigid metal notched gages, also called step or comb gages, in the measurement of wet film thickness of organic coatings. ASTM Test Method D 1212 covers the determination of wet film thickness of organic coatings using the Interchemical wet thickness gage and the Pfund gage.


Subjective term used to describe the lightening of the color of a pigmented paint following exposure to the effects of light, heat, time, temperature, chemicals, etc.

The observed fading may result from deterioration of the pigment, from deterioration of the vehicle, or from a decrease in gloss. A separation of the vehicle from the pigment particle in the interior of the film, with the subsequent introduction of microvoids, which scatter light, may also be interpreted visually as fading.

Flash Rusting

A form of corrosion that occurs during the drying process of a water-based coating. Water-soluble corrosion products migrate to the surface of a coating and appear as a stain.

An example of this is the appearance of a brown stain a few minutes after a plain steel nail is coated with a white latex paint. The currently accepted test method used to evaluate coatings as to their performance in flash rusting situations can be found in ASTM D 2247-68. A more sophisticated method can be found in Journal of Coatings Technology 65, No. 827, p. 45 (1983).

Additives used for the inhibition of flash rusting are basically of two types. The first is a liquid or soluble additive, such as alkylamines, amino alcohols, and others, which are used at 0.1 to 2% on the total weight of the formula. The second type is corrosion inhibiting pigments, which must be ground into the paint and are only trace soluble in the water media. Both inhibitor types are also of direct benefit to the paint manufacturer in that they will inhibit the corrosion of the can.

Freeze-Thaw Resistance

The extent to which water-based paints, utilizing synthetic latex or synthetic resin emulsions as vehicles: (1) retain their original properties, free from detrimental changes in consistency, and (2) resist coagulation, or the formation of lumps and specks, when subjected to freezing and subsequent thawing. (ASTM)

After leaving the plant, paints are sometimes shipped and/or stored at low temperatures where they can freeze. If the paint develops viscosity instability or contains grit or gel after thawing, it may no longer be usable. ASTM Test Method D 2243 covers the determination of the extent to which waterborne coatings retain their original properties free of detrimental changes.

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Glass Transition

The transition temperature range (relatively small for most polymers) within which an amorphous polymer changes from a rubbery or viscous to a glass-like (brittle) state. Syn: second order transition

This may be evidenced by a change in the slope of a stiffness-temperature curve, dielectric properties-temperature curve, etc.

Glass Transition Temperature

(Tg) Temperature at which the noncrystalline portion of the polymer is transformed from a tough, rubbery material to a brittle, glass-like material.

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To prevent the passage of heat, electricity, or sound into or out of, especially by surrounding with a nonconducting material.

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Krebs Units

(KU) Values of a scale commonly used to express the consistency of paints generally applied by brush or roller. (ASTM)

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1. Stable dispersion of a polymeric substance in an essentially aqueous medium.

2. Fine dispersion of rubber or resin, natural or synthetic, in water; the synthetic is made by emulsion polymerization.

Strictly speaking, after polymerization, latex is a solid dispersed in water and, therefore, is not an emulsion. Latex and emulsion are often used synonymously in the paint industry. Generally accepted plurals are lattices or latexes. ASTM test methods for latexes include: filter-retained solids content, D 5097; guides to test procedures, D 4143; nonvolatile content (solids), D 4758; unreacted monomer content, D 4827, D 4747.

Latex Heat Age Stability

The ability of latex to resist drastic change in pH and viscosity, as well as skin formation, which could occur as the result of being subjected to a constant temperature of 140°F for 10 days or to occasional exposure to high temperatures over a longer period of time.

A generally accepted guideline is that 10 days at 140°F is roughly predictive of one year in a warehouse. Latex heat age stability is critical, because in shipment or in storage, latex can be subjected to high temperatures for extended time periods.

Latex Mechanical Stability

The ability of latex to resist coagulation under the influence of mechanical agitation. (ASTM)

Latex Paint

A paint containing a stable aqueous dispersion of synthetic resin, produced by emulsion polymerization, as the principal constituent of the binder. (ASTM) Modifying resins may also be present.

Latex Room Temperature Stability

The ability of latex to maintain its initial property/physical condition after allowing the sample to stand undisturbed for a long period of time (usually six months to a year).

Property changes can be in pH, viscosity, sedimentation, skin formation, phase separation, settling, etc. These are indicators of how sensitive a latex is to stresses encountered during shipping or extended storage at ambient temperature.


The measure of the ability of a wet coating to flow out to a smooth dry film after application so as to obliterate any surface irregularities such as brush marks, roller marks, orange peel from spraying, peaks, or craters, which have been produced by the mechanical process of applying the film. (ASTM)

Leveling leads to uniformity of the surface of the coating. Uniformity favors hiding, imaging, dirt release and durability with respect to corrosion, cracking, and blistering. Brush marks and other imperfections left in the film are normally undesirable particularly in semigloss and gloss finishes where these irregularities are more readily apparent.

Leveling integrates the effects of gravity, film thickness, drying time, rheology, and surface tension. It also varies with humidity, airflow, temperature, porosity of the substrate, and on the orientation of the painted surface, viz., horizontal up, horizontal down, or vertical, as well as the direction of the brush strokes on a vertical surface. ASTM Test Method D 4062 covers the laboratory determination of the relative leveling or water and solvent-reducible architectural paints by comparing the ridges produced in a drawdown film to a series of plastic leveling standards.

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Mandrel Bend Test

Test for determining the flexibility and adhesion of surface coatings, so named because it involves the bending of coated metal panels around mandrels.

Coatings attached to substrates are elongated when substrates become elongated while being bent during the manufacture of articles or when the articles are abused in service. ASTM Test Method D 522 covers the determination of the resistance to cracking (flexibility) of attached organic coatings on substrates of sheet metal or rubber-type materials.

Material Safety Data Sheet

(MSDS) OSHA's established guidelines for the descriptive data that should be concisely provided on a data sheet to serve as the basis for written hazard-communication programs. The thrust of the law is to have those who make, distribute, and use hazardous materials be responsible for effective communication.

The purpose of an MSDS is to inform the user about the material's physical properties or fast acting health effects that make it dangerous to handle; the level of protective gear that you need; the first aid treatment to be provided when one is exposed to a hazard; the preplanning needed for safely handling spills, fires, and day-to-day operations; and how to respond to accidents.

A comprehensive MSDS access, storage, and retrieval system on CD-ROM, called Panorama® is available from the FSCT.


Movement of certain materials in a coating or plastic (e. g., plasticizers in vinyl) to the surface or into an adjacent material.


A unit of length equal to one thousandth of an inch (0.0254 mm).


1. Superficial growth produced on organic matter or living plants by fungi (as of the families Erysiphaceae and Peronosporaceae).

2. A fungi producing mildew.

3. A discoloration caused by fungi.

Two types are common:

1. filamentous - thread-like structures, gray to black in color, which make up the mycelium or vegetative form of fungi.

2. spores-spherical or nodular bodies, gray or black in color, which may or may not be associated with fungal mycelia. Spores are the reproductive form of fungi. (Mildew should not be confused with algae, which are usually green to brown in color, and normally occurs in shaded damp areas.)

Mildew can be distinguished from dirt by using bleach such as Clorox®. A drop of bleach is placed on the area in question and allowed to run down the area. If the discoloration turns lighter, then the discoloration is mildew. If it doesn't change, it is dirt. Mildew, unlike dirt, is very difficult to remove from the film. If the film is washed with water, dirt will be removed, but the mildew will remain imbedded in the film as a dark stain. The two can also be differentiated with a microscope

. Mildew (Fungus) Resistance

The ability of a coating to resist superficial fungus growth that can cause discoloration and ultimate decomposition of a coating's binding medium. See mildew.

Mildew collection is the phenomenon of a coating manifest by the presence of mold or fungus growth of a type familiarly known as mildew. Two types are common: (1) the spore type, which resembles caviar in appearance; and (2) the mycelium or filament type. A microscope is necessary to differentiate the spore type from dirt collection. The mycelium type is often recognized with the naked eye when it reaches an advanced stage, but a microscope is recommended for any mildew examination. The FSCT Pictorial Standards for Coatings Defects contains photographic standards for evaluating the degree of surface disfigurement of paint films by fungal growth or soil and dirt accumulation. ASTM Test Method D 3274 also has these same photographic reference standards to provide a numerical basis for rating the degree of fungal and algal growth or soil and dirt accumulation on paint films.


Chemical agent that destroys, retards, or prevents the growth of mildew.

Moisture Vapor Permeability

(MVP) See specific permeability (of a film to moisture).

ASTM Test Method D 1653 covers the determination of the rate at which water vapor passes through films of paint, varnish, lacquer, and other organic coatings. The films may be free films or they may be applied to porous substrates.

Moisture Vapor Transmission

(MVT) Rate of movement of moisture vapor through a membrane.

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Nonvolatile Matter

(NVM) or content of a coating The solid material remaining after the volatiles have been driven from the film under specified test conditions. The total percentage volatile present is obtained by subtracting the nonvolatile content from total solids. {ASTM) Syn: solids

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The degree to which a material obscures a substrate, as opposed to transparency, which is the degree to which a material does not obscure a substrate. See contrast ratio and hiding power.

Opacity is sometimes described in terms of the contrast ratio.


Impervious to light rays.


1. The chemical process by which the oxidation state of an atom in an element, ion, or compound is increased. (IUPAC)

2. The formation of an oxide or, more generally, any increase in valence of an element.

3. In coatings, the introduction of oxygen into a molecule thereby producing a cured (or degraded) film.

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The presence of numerous minute voids in a cured material. Also may refer to open cells in skin of cellular rubber, and in this case is not a defect.

ASTM Test Method D 3258 covers the determination of the porosity of a white or near white, mineral spirits insoluble, paint film to indicate the degree to which a subsequent coat will penetrate.

Particle Size in Paints

The diameter of a pigment or latex particle; usually expressed in mils or micrometers. (DAC)

ASTM test methods for particle size (analysis/distribution) include coarse particle content, D 185; pigments, reporting characteristics, D 1366; polymeric powder properties, D 3451; and white extender pigments, D 3360.

Particle Size Distribution

The relative percentage by weight or number of each of the different size fractions of particulate matter. (ASTM)


Detachment of a coating film from the underlying surface or undercoating, in ribbons or sheets, generally accompanied by curling of the edges.

Peeling can be considered as an aggravated form of flaking (scaling). It is frequently due to collection of moisture beneath the film.

Perlite, Expanded

1 NA2O.1 K2O.2.5 A12O3.19.5 SiO2 A unique form of siliceous lava that is characterized by many spherical and convoluted cracks. Syns: pearlstone, ground perlite, pearlite

The interior or internal structure causes it to break up into small spheres or "pebbles". Perlite expands when heated at a range of 720°C (1500°F) to 1090°C (2000°F) to 10 to 20 times its initial volume. Used as insulation and filler, also extender. Density, 2.2 g/cm3 (1.87lb/gal); particle size, 44 µm.


A unit of measurement of water vapor permeance; a metric perm, or 1 g/24 h0m20mm Hg. or U.S. unit, 1 grain/h0ft20in. Hg. (ASTM) See water vapor transmission (WVT) and perm cup or dish.

Perm is used to express the resistance of a material to the penetration of moisture.

Perm Cup or Dish

A container made of non-corroding material, impermeable to water or water vapor. It is used to measure water vapor transmission rate and/or water vapor permeance.


Resistance of any object or material to change with age or exposure to deleterious conditions.


The negative logarithm of the hydrogen ion concentration, in mol/litre. Measure of the acidity or alkalinity of an aqueous solution. pH = 7 represents neutrality, i.e., the solution is neither acid nor alkaline. pH values from 0 to 7 are acidic - the lower the pH value, the higher the degree of acidity. pH values from 7 to 14 represent alkalinity. The higher the pH value above 7, the greater the degree of alkalinity.

The stability and/or viscosity of many latex paint systems are dependent upon pH. In order to assess pH stability, the pH of the paint should be determined after heat aging, shelf aging, and freeze/thaw cycling.


Finely ground, natural or synthetic, inorganic or organic, insoluble dispersed particles (powder) which, when dispersed in a liquid vehicle to make paint, may provide, in addition to color, many of the essential properties of a paint-opacity, hardness, durability, and corrosion resistance.

The term is used to include extenders, as well as white or color pigments. The distinction between powders which are pigments and those which are dyes is generally considered on the basis of solubility-pigments being insoluble and dispersed in the material, dyes being soluble or in solution as used.


Film defect characterized by small pore-like flaws in a coating, which extend entirely through the applied film and have the general appearance of pinpricks, fine holds, or voids when viewed by reflected light. (ASTM)

The term is rather generally applied to holes caused by solvent bubbling, moisture, other volatile products, or the presence of extraneous particles in the applied film. ASTM Test Method D 1848 recognizes pinholes as a paint film failure characteristic of exterior latex paints.


The process of increasing the flexibility and adhesion of an organic coating film and decreasing its brittleness, cohesiveness, and glass transition temperature. It can be achieved by chemical modification of the polymer (internal plasticizer) or by adding compounds (plasticizers) to the coating formulation (external plasticizer).


1. An additive in a paint formulation to soften the film, thus giving it better flexibility, chip resistance, and formability.

2. A chemical agent added to a plastic composition to improve its flow and process ability and to reduce brittleness. (DAC)

See plasticization.

Plasticizer Migration

Movement of plasticizer in a coating or plastic to the surface or into an adjacent material such as an undercoat or substrate.


1. 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 name is also frequently applied to large molecules produced by any chemical process, e.g., condensation in which water or other products are produced; alkyd resins are examples of these. Homopolymer - polymer of which the molecules consist of one kind of structural unit repeated any number of times; polyvinyl chloride and polyvinyl acetate are examples. Copolymer - polymer of which the molecule consists of more than one kind of structural unit derived from more than one monomer. Polyvinyl chloride-acetate, or polyvinyl acetate-acrylic copolymers are examples.

2. A substance consisting of molecules characterized by the repetition (neglecting ends, branch junctions, and other minor irregularities) of one or more types of monomeric units. (IUPAC) Syn: macromolecule

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An accelerated weathering machine that simulates the deterioration, caused by water as rain and dew and the ultraviolet light energy in sunlight, of outdoor materials.

The tester simulates the effects of sunlight by fluorescent UV lamps, and simulates. rain and dew by direct condensation of water on the test specimen. It is not intended to simulate the deterioration caused by localized weather phenomena, such as atmospheric pollution, biological attack, and salt water exposure. For testing, see ASTM Test Method G 53.

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Reflectivity (R?)

1. Reflectance that would be attained if a material was completely opaque; reflectance of a layer of material of such thickness than an increase in thickness will not change its reflectance.

2. The reflectance of a film so thick that a further increase in thickness does not change the reflectance.

ASTM test methods for both reflectance and reflectivity include: gray scale, evaluating color change, D 2616; hiding power by reflectometry, D 2805; instrumental color difference, D 2244; Munsell color system, D 1535; of opaque specimens, E 97; preparation of reflectance standards, E 259; specific luminance, traffic coatings, D 4061.


Deflection of radiant energy from a straight path in one medium to a different path in another medium of different index of refraction.


The reddish, brittle coating formed on iron or its alloys resulting from exposure to humid atmosphere or chemical attack.

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Scrub Resistance

The ability of a coating to resist being worn away or to maintain its original appearance when rubbed repeatedly with an abrasive material. Typically, the rubbing procedure can employ a brush, sponge, or cloth, wetted with an abrasive soap solution, in which case it is more accurately referred to as wet scrub resistance. Syn: wet abrasion resistance


An attribute of object mode of appearance, which is similar to luster; gloss with poor distinctness of image reflectance.

In the paint industry the term sheen is generally used synonymously with gloss measured or observed at a grazing angle, such as 85° off the perpendicular. Sheen is therefore frequently evaluated in terms of gloss measurements made on an 85° glossmeter. Not infrequently there are coatings that are high in sheen, but have a low gloss when illuminated and viewed at or near the perpendicular.

Sheepskin Paint Roller Cover

A cover in which the paint application material is wool fleece still attached to its tanned natural skin. (ASTM)

Shelf Life

The period of time in which a material may normally be stored and still be in a usable condition. Syns: staging life and pot life


Alcohol-soluble, orange-colored resin, which is the secretion of the female of the insect (Laccifer lacca) found in great quantities in India and Indochina.

Shellac appears as an incrustation on the twigs of certain trees. It forms the basis of French polish and several other types of spirit varnish and is used for adhesive purposes, because of its thermosetting properties.

Solids by Volume

The volume of the nonvolatile portion of a composition divided by the total volume, expressed as a percent. Syn: volume solids

Spreading Rate

The average area covered by a specified volume of coating when applied over a normal surface in a manner appropriate for that coating.

Spreading rate will vary with operator, the method of application, and the nature of the surface being coated. Spreading rate is frequently expressed as ft2/gal or m2/litre.


1. Any surface to which a coating or printing ink is applied.

2. The nonpainted material to which the first coat was applied, sometimes referred to as the original substrate.

3. Base on which organic coloring agents are precipitated to form lakes.

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Tinting Strength

Measure of the effectiveness with which a unit quantity of color alters the color of a material. (ASTM)

For scattering and absorbing colors (pigments), both absorption and scattering tinting strength must bed specified. Tinting strength may be one factor in judging the relative economic value of paints, since pigment concentration contributes to strength in a major way; other factors are formulation and color development in grinding. The user may also select products for other properties, such as transparency, that are accompanied by different tinting strengths. ASTM Test Method D 4838 determines the relative tinting strength of chromatic paints.

Tire Pick-up Resistance

The ability of a latex paint to maintain adhesion and resist imprint and black marks of tire treads when applied to a concrete surface.

Water-based coatings do not penetrate into cementitious surfaces and therefore lack the adhesion of solvent-based coatings. The alkalinity of the cementitious surface is a factor with certain systems.

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1. State or quality of being viscous.

2. The property of a fluid whereby it tends to resist relative motion within itself. If different layers of fluid are moving with different velocities, viscous forces come into play, tending to slow down the faster-moving layers and to increase the velocity of the slower-moving layers.

The constant of proportionality is called the coefficient of viscosity of the fluid. Measured in Newton seconds per square metre (SI units) or poise (c.g.s. units). 1 centipoise = 10-3 Ns/m2 or pascal-seconds (Pas) which are equivalent to 10 poise.

Volatile Organic Compound

(VOC) Any organic compound which participates in atmospheric photochemical reactions; that is, any organic compound other than those which the EPA designates as having negligible photochemical reactivity. (This is derived from EPA's official definition.) Syns: volatile organic substances; photochemically reactive organic substance

VOC may be measured by a reference method, an equivalent method, an alternative method, or by procedures specified under any subpart. A reference method, an equivalent method, or an alternative method, however, may also measure nonreactive organic compounds. In such cases, an owner or operator may exclude the nonreactive organic compounds when determining compliance with a standard. The Administrator has designated the following organic compounds as negligibly reactive: methane, ethane, 1,1,1-trichloroethane (methyl chloroform), methylene chloride (dichloromethane), dichlorotrifluoroethane (HCF-123), tetrafluoroethane (HCFC-134a), dichlorofluoroethane (HCFC-141b) and chlorodifluoroethane (HCFC-142b), trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), chlorofluoromethane (CFC-22), trifluoromethane (CFC-23) trichlorotrifluoroethane (CFC-113), dichlorotetrafluoroethane (CFC-114) and chloropentafluoroethane (CFC-15).

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Ease with which the dirt can be removed from a paint surface by washing; also refers to the ability of the coating to withstand washing without removal or substantial damage.

Water Vapor Permeance

(WVP) The steady water vapor flow in unit time through unit area of body (WVT) induced by unit vapor pressure difference (?p) between the two surfaces of a coating. Therefore, WVP = WVT/?p. See water vapor transmission rate (WVP), perm. (ASTM)

Accepted inch-pound unit is grains per square foot per hour per inch of mercury (called a perm). Accepted SI unit is grams per square metre per 24 h per millimeter of mercury (called a metric perm). One of the factors affecting the performance provided by an organic coating is the degree of resistance to the passage of water vapor. Hence, the water vapor transmission characteristics of coatings are important in assessing their performance in practical use. ASTM Test Method D 1653 covers the determination of the rate at which water vapor passes through films of organic coatings. The films may be free or they may be applied to a porous surface.

Water Vapor Transmission Rate

(WVT) The steady water vapor flow in unit time through unit area of a body, between two specific parallel surfaces, under specific conditions of temperature and humidity at each surface. (ASTM) See water vapor permeance (WVP) and perm.

Accepted inch-pound unit is grains per square foot per hour. Accepted SI unit is grams per square metre per 24 h. One of the factors affecting the performance provided by an organic coating is the degree of resistance to the passage of water vapor. Hence, the water vapor transmission characteristics of coatings are important in assessing their performance in practical use. The water vapor transmission is not a linear function of film thickness, temperature, or relative humidity. ASTM Test Method D 1653 covers the determination of the rate at which water vapor passes through films of organic coatings. The films may be free or they may be applied to a porous surface.

Water-Based Coatings

Coatings in which the volatile content is predominantly water. These include latex paints, emulsion paints, and water paints. Syns: waterborne coatings and water reducible coatings

Weight Percent Solids

The portion of a coating that remains as part of the dry film expressed as weight. (ASTM) See nonvolatile matter. Syns: solids, total solids

Another convention of expressing solids content is by volume percent.

Wet Adhesion

The ability of a coating film to adhere tightly to a substrate directly beneath it under wet conditions such as rain, dew, washing, etc. (ASTM)

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Development of a yellow color on aging; most noticeable in the dried films of white paints or clear varnishes. (BSI)

Primary cause of yellowing is the formation of color bodies due to oxidation of the oil or other unsaturated components of the binder.

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