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Glossary

Additive Any one of a number of special chemicals added to a coating material to bring out special effects.
Adhesion, chemical Attachment of a coating film to a surface by actual chemical attack which changes the character of the coated surface.
Adhesion, intercoat The ability of coatings to adhere to one another.
Adhesion, intracoat The ability of a coating film to maintain its internal integrity without separating or layering.
Adhesion, mechanical Attachment of a coating film to a surface by molecular attraction without altering the coated surface.
Agglomerate A cluster of particles.
Aging Changes which take place in a material as a result of the passage of time.
Alligatoring Contraction of a film forming small irregular islands of the film with cracks in between. When an overprint breaks up over the undercoat. This happens with ceramics when the undercoat is lower melting than the overcoat. This also happens when a UV curable enamel is not uniformly cured.
Antioxidant Agent which retards skin formation on the surface of coatings subject to oxidation.
Art work A design intended for reproduction.
Backlap An extremely heavy, eneven application of color at one edge of a print.
Backlash Same as Backlap.
Bake A heat treatment used to hasten the drying or curing of a film.
Baking cycle The time and temperature combination used to develop maximum properties of an organic film.
Base A resin or frit type that determines the characteristics of the coating material.
Belt marks See Chain marks.
Binder 1. An addition to a ceramic coating which, after drying, will provide suficient film hardness to permit handling and will burn away during firing.
2. A major component in an organic system which, with or without pigments, forms the final film.
Black light A common name for ultraviolet light.
Bleaching Partial or complete loss of color. Fading.
Bleeding Migration of color from the coating film onto or into a surface with which it comes in contact. The amber or blue color that is sometimes seen under the silver busbar.
Blister A profusion of ubbles in a coating film that form during the heat treating process and remain after the film solidifies. In baking films, it is usually caused by solvent entrapments as a result of too high a baking temperature too early in the bake cycle. Surface disruption in extreme cases. Frequently accompanied by a sliht color change. Carbon entrapment in ceramic coatings. Ceramic coating can easily be scratched with knife blade or other hard object.
Blocking Unwanted sticking of succeeding layers of one coated substrate to another when stacked after drying caused by inadequate drying. Pack-off, Offsetting.
Bloom 1. A milky haze on the surface of a coating film usually caused by rapid solvent evaporation resulting in condensation of moisture on the film.
2. A stain on glass as a result of atmospheric action.
3. An iridescence on the surface of a transparent silver stain.
Blur See Smear, Halo, Ghost.
Blush A hazy or foggy appearance in a coating film caused by the absorption of water vapor into the drying film due to rapid evaporation of solvent. Bloom.
Body Term used to describe the viscosity, flow, and general consistency of a coating material.
Bond Degree of adherence of a coating to a substrate.
Boiling See Blister.
Bubbles Air trapped in the coating due to surface tension. Gases or water vapor trapped under a solidified film.
Calendered fabric Screen mesh material that has been flattened by metal rollers on one or both sides to reduce fabric thickness and decrease open area.
Catalyst A substance which initiates or accelerates the speed of reaction between the other components of a coating formulation.
Ceramic coating An inorganic, essentially non-metallic coating, fused to a substrate at or above red heat.
Chain marks Marks on the substrate caused by chains, belts, or other support systems used to convey the substrate through the heat cycle.
Chalking The powdering of the surface of a coating film as a result of exterior exposure and/or breakdown of the resin base.
Checking Fine hairline cracks in a dried coating film which begin at the surface and progress downward.
Clogging A restriction of the passage of a coating material through the application equipment.
Cobwebbing A condition caused by static electricity combined with low humidity and a fast evaporating solvent in which fine strings of coating material actually resemble cobwebs are propelled from the source to the nearest ground. Occurs frequently in screen printing when static electricity builds up in the screen caused by the friction of the squeegee against the mesh.
Coefficient of expansion - linear Change in fractional length that a material elongates with one degree temperature increase.
Color variation Noticeable color differences over the coated area on the same piece.
Combustion Rapid oxidation or burning.
Compatibility The ability of coating material, solvents, and substrate to function together in an accaptable manner.
Component A part of a whole. An ingredient in a coating formulation.
Cracking Breaking up of the coating film. Varying in size from very fine cracks (Crizzle) to very large cracks (Alligatoring). Usually penetrates the entire film thickness.
Craters Small, shallow areas, circular in shape, in a coating film which may or may not expose the underlying substrate. Can vary in size from a tiny spot to an inch or more in diameter.
Crawling Pulling away of a coating film from the original dimensions of the coated area. Creeping, Fish eyes, Pull-back, Shrinking.
Crazing 1. Hairline cracking of a ceramic coating after firing due to internal stresses of tension or compression.
2. In organics, formation of surface cracks, often as a fine network, which do not penetrate to the substrate. Checking.
Creeping 1. A mild form of Crawling.
2. The tendency of an insufficiently stretched printing screen to move in the direction of the squeegee travel during the print stroke.
Crizzle Fine surface cracks in a ceramic coating. Usually appears in second or additional overprints but can be present in the first coat as well.
Cross-linking Connecting crosswise in parallel chains the atoms or atomical group in a complex molecule.
Cure Converting a wet coating to its maximum dry film properties by chemical cross-linking. May require heat or U.V. radiation to initiate or hasten the reaction.
Curing agent An additive that promotes the curing of a coating film.
Curling See Peeling.
Dark reaction A condition in wherein a U.V. coating hardens or polymerizes without any exposure to a U.V. light source. Also know as dark hardening.
Deflocculant An additive to disperse a suspension of ingredients in a vehicle so that it has little tendency to settle and has a slower viscosity.
Delamination Separation of a layer of one material from another.
Devitrification A change in a ceramic coating resulting in a loss of gloss due to crystallization.
Digs Defects in a coating film usually caused from accidental impact to the film by a foreign object such a the corner of another substrate or other hard object.
Dilatent A property of a fluid in which the resistence to flow increases as the force exerted on the fluid is increased.
Dimples A shallow depression in a coating film. Relatred to Craters.
Distorted image Screen printed image fails to fall within required dimensions.
Dip-through Color seeping through a screen while covering an image area.
Drying Converting a wet coating to dry film by removal of solvents at ambient or elevated temperatures.
Drying in Premature drying of a coating material in the image area of the printing screen, resulting in loss of detail or failure of the coating to transfer from the screen to the substrate.
Dull finish Coating does not display normal degree of gloss.
Enamel 1. A term loosely applied to a resin based coating that dries hard with some degree of gloss.
2. In ceramics, a powdered mixture of frit and pigment for application to glass or metal.
Epoxy A term used for a family of resins with excellent adhesions. Usually forms a very strong film with excellent chemical resistance. Supplied as one-part systems (catalyst already added) and two-part systems (resin and catalyst separate). One-part sytems have shorter shelf life and must be heat cured. Two-part systems have a short pot life.
Exposure The length of time that a coating film is subjected to environmental influences.
Extender A material used to increase the volume of a coating without thinning and without affecting the properties of the coating other than diluting the color intensity.
Fading Partial or complete loss of color. Bleaching.
Fat A term used to describe a coating material which has good flow characteristics. Opposite of Short.
Film A thin continuous layer of a substance, such as, but not limited to, a coatig material.
Fire The heat treating process in which a ceramic coating is fused to a substrate.
Firing cycle The time and temperature combination used to fuse a ceramic coating to a substrate.
Fish eyes Defects in a coating film, circular in shape, usually resulting in contamination of a substrate surface. The coating material will not wet this surface, and, as a result, will pull back, exposing the substrate. May vary greatly in size and distribution. Frequently resembles Craters.
Flaking Detachment of small area/chips of a coating film from the surface to which it was applied due to loss of adhesion.
Floating Tendency of pigment particles in a wet film to separate and concentrate in particular areas.
Flocculent An electrolyte which, when added to a coating material, will cause solid particles to aggregate and settle due to the reduced degree of repulsion between the particles.
Flocculation A loose aggregation of primary pigment particles which can be broken down by mild shear forces.
Flood coat 1. The spreading of a layer of coating material over the image area of a printing screen without actually printing. This serves two purposes:
a. To keep the image area wet so as to reduce any tendency for the screen to dry out and clog
b. To provide an adequate supply of coating material for the printing cycle.
2. In manual printing, to flood immediately after printing.
Flooding The tendency of pigment particles to rise to the surface during drying/curing and produce a uniform color which is different from that of the surrounding film.
Flood pull In machine printing, to flood just before printing.
Flood stroke That portion of the printing cycle where the coating material is pulled from the end of the print sequence back across the screen to the beginning of the print stroke while the screen is above and/or out of contact with the substrate.
Flow The ability of a coating material to spread over a surface.
Flux A form of low melting glass which forms the permanent vehicle in a ceramic glass enamel. Frit.
Foam The proliferation of a vast number of bubbles in and on the surface of a wet coating material, frequently caused by high speed mixing which indices air into the liquid mixture.
Focal distance The ideal distance between substrate and the U.V. light source for curing U.V. coatings.
Frit A form of low melting glass which forms the permanent vehicle of aluminum enamels, glass enamels (see Flux), and ceramic overglaze colors.
Gelling An increase in the body of coatings as a result of gelatin or chemical reaction in storage. Livering.
Ghost An image, thin and somewhat ragged, which extends beyond the actual image area of a printing screen and is caused by the tendency of a screen with insufficient tension to move in the direction of the squeegee travel during the print stroke. Blur, Shadow, Smear, Halo, Slur.
Half-tone A printed design in which the image is produced by a series of dots, the concentration of which determines the density of the color shade.
Halo 1. A hazy area around a fired ceramic decoration.
2. An image, thin and shadowy, which extends beyond the image area of the print, caused by the movement of the printing screen during the print stroke. Ghost, Shadow, Blur, Smear.
Hickey An imperfection in a coating film from numerous causes such as dirt, dust, fuzz, lint, hardened specks of coating material, etc., having become stuck to or embedded in the wet film
Hiding power The ability of a coating to mask or block out the substrate. Opaque.
Hygroscopic The ability of some materials to absorb atmospheric moisture.
Image The reproduction of a design in a printing screen.
Ink A term frequently applied to screen printable mixtures.
Inorganic coatings Coatings made from elemental (mineral) sources
Iridescence A surface rainbow effect, similar to oil-on-water appearance.
Lifting The softening of subsequent penetration of a coating layer by another coating which causes the first layer to raise and/or release.
Livering See Gelling.
Medium The organic liquid or the carrying agent of coating materials. Vehicle.
Mesh marks A crosshatch pattern that remains in a screen printed film after the screen releases from the print. This is due to insufficient flow and/or levelling of the coating film.
Migration Movement of one or more substances in a coating film into or onto another layer of film or substrate.
Moiré 1. Irregular lines in a coating film caused by uneven drying. Shorelining.
2. A pattern in the coating film caused by incorrect screen mesh angles in multiple coating applications of half-tones.
Monomer A single unit molecule used in combination with oligomers in formulationg U.V. curable coatings.
Mottle A blotchy appearance in a coating film caused by flooding and floating of pigment particles and electrostatic attraction. Most noticeable in metallic coatings.
Newtonian A term used to describe the rheological characteristics of a liquid that has an absolute viscosity, i.e., water, that does not change with temperature fluctuations or shear rate.
Newton's rings An effect caused by light passing through layers of transparent films with air trapped in between, causing refraction of the light rays.
Off-contact The distance between the print side of a printing screen and the substrate surface.
Offsetting See Blocking.
Oligomer A multiple unit molecule consisting of several mononumeric units chemically combined. Used in formulating U.V. curable coatings.
Opaque Not able to transmit light.
Orange peel A rough surface texture on a coating film having the appearance of an orange peel, usually caused by a too viscous coating material. Common in enamels.
Organic coatings Coatings made from raw materials of animals or vegetable origin, not elemental (mineral), although in some cases mineral pigments may be used.
Overture An undesirable condition in which a coating is overexposed to the curing process, resulting in an excessively hard surface that may prevent additional coating layers from adhering. May also have a detrimental affect on color shade in organic based coatings.
Overfire Heating to a temperature which causes damage to substrate, undesirable color changes, or devitrification of ceramic coatings.
Oxidation The hardening of a coating film by reaction with oxygen. Forming an oxide of a metal by chemical reaction of the metal in the presence of oxygen.
Pack-off See Blocking.
Peeling Detachment of a coating film from a substrate. Shivering, Curling.
Photo initiator A light absorbing chemical used in light sensitive coatings to initiate the polymerization process.
Pick-up A condition where a coating film form a previous printing operation will adhere to the underside of a printing screen during an overprinting operation.
Pigments Materials which add color, body and opacity to coatings.
Pinholes Tiny, transparent openings in a coating film that can be attributed to surface contamination, cracks, dirt, coating contamination, surface tension, static electricity, screen clogging, abrasion of the film, agglomerates in the coating, rapid solvent loss, etc. Any small hole that permits the passage of light.
Pock marks See Crater, Fish eyes.
Polymer A long chain molecular structure formed by a reaction between monomers and/or oligomers.
Polymerization A chemical process brought about by the reaction of light, heat, or a catalyst causing monomers and/or oligomers to combine, forming a polymer.
Popping The fracturing or rupturing of a coating film caused by escaping gases or water vapor trapped under the surface.
Pot life The length of time that a coating material will remain useful without excessive deterioration.
Preheat The period of time to which a coating film and substrate are subjected at a lower temperature than that which will produce the final hardening or firing of the film
Print stroke That portion of the printing cycle where the squeegee travels the distance of the image area while forcing the screen into contact with the substrate and at the same time pushing the coating material throught the open mesh and onto the substrate.
Pull-back See Crawling.
Ragged lines Uneven, jagged, distorted, generally poor quality screen printed image. Sawtooth.
Railroading The bouncing and jerking action of a squeegee on a screen when printing closely spaced parallel lines which are also parallel to the squeegee. The severity of this action is dependant upon the emulsion thickness and squeegee pressure.
Reactor A U.V. curable unit consisting of U.V. lamp(s), reflectors, cooling system, and shielding. May also include the conveying system.
Registration The ability to establish and maintain the location of a coating with reference to another coating or to the substrate to which it is applied.
Relative humidity The amount of water vapor in the air compared to the maximum amount that the air can hold at that temperature, expressed in percentage.
Resin The film forming component of a oating material.
Retarder Additive that slows the drying time of a coating material, usually a slow drying (high boiling) solvent.
Rheology The study of the flow characteristics of liquids.
Rough image See Ragged lines, Sawtooth.
Rubs Defects to a coating or substrate caused by friction or abrasion.
Running The action of coating film which causes it to spread beyond the original dimensions of application. Sagging, Weeping, Creeping, Slump.
Sagging A mild form of running.
Sandy finish A rough sand-like surface on a coating film.
Sawtooth Uneven edge difinition in a screen printed design caused by inadequate thickness of emulsion or insufficient exposure of the emulsion which results in the emulsion, during the wash-out operations, breaking free of an entire mesh opening, following the contour of the mesh, instead of the image.
Scallop A condition of Crawling in which the edges of the coated area pull back resulting in a scallop-like appearance.
Screen marks A pattern of the screen mesh in the printed film.
Scum 1. A dull area in a glossy coating film.
2. A residue left in the image areas of a printing screen due to failure to inadequately wash out the emulsion.
Shadow See Ghost, Halo.
Shelf life The length of time which a product can be stored and still be useable.
Shivering See Peeling.
Shorelining See Moiré.
Short A term used to describe a coating material which exhibits a lack of flow; a buttery or clay-like consistencey. Opposite of Fat.
Shrinking See Crawling.
Silking A defect in coatings saused by the tendecy of pigment particles in the film to concentrate or settle, as the coating flows away from the edges or holes in the substrate. This is usually caused by a heavy application of a low viscosity coating.
Silting See Silking.
Skin finish Fine blisters in a fired ceramic coating, covered by a smooth film, or skin, which can be scratched with a knofe or other hard object.
Skinning A dried film on the surface of a coating in a container caused by absorption and reaction with oxygen. Common in air drying enamels.
Sliding A condition where a coating actually slides or slips intact from its original location to another position on the substrate. Caused by moisture condensed on the substrate under the coating material.
Slipping See Sliding.
Slump See Running, Sagging.
Slur See Ghost, Halo, Smear.
Smear A defect in a coating caused by accidental handling or movement of the printing screen or substrate during application of the coating film. May also be caused by momentary sticking of the printing screen to the printed substrate during the print stroke.
Smudge See Smear.
Solvent A thinning, resolving or reducing agent.
Spall Chip or fragment removed from surface of a coating as a result of impact or spontaneous action.
Specks Tiny particles of contamination in a coating film.
Spotting 1. Residue on a substrate from droplets or streaks of water, usually alkali salts or containing some other previously dissolved substance.
2. Residue on a substrate from oil, such as cutting oil or lubricant. Both may cause coating defects.
Starburst See Starlight.
Starlight A defect in a coating film which exibits severe proliferation of tiny pinholes, sometimes only visible by backlighting. May be localized or throughout the coating. May or may not be visible prior to firing, depending on the cause.
Static electricity An electrical charge on a substrate or application equipment, usually initiated by friction in combination with low humidity.
Streaks Elongated defects.
Stringing Small hair-like particles of coating material which are attracted to the substrate. Caused by static electricity. See Cobwebbing.
Substrate The base stock or material to which a coating is applied.
Sulphide Stain A metallic-appearing gray-like scum on a fired ceramic surface which develops during storage of the decorated product. Caused by sulpher containing packaging or atmospheric attack.
Tearing See Alligatoring, Cracking.
Thinner A liquid which reduces viscosity and/or extends a coating material.
Thixotropy The ability of a coating material to thicken on standing but to regain flow with agitation.
Ultraviolet The part of the spectrum where the wave length is shorter than that of visible light.
Ultraviolet coating or ink Inks or coatings which have been formulated to react or polymerize with exposure to intense ultraviolet light rays.
Ultraviolet curing The process of polymerization; a reaction initiated by the presence of ultraviolet light.
Ultraviolet light The part of the electromagnetic spectrum between 200 and 400 nm in wavelength.
UV Abbreviation for ultraviolet.
Vehicle The carrying agent of coating materials. Medium.
Viscometer An instrument for measuring the resistance of a liquid to shear or flow.
Viscosity 1. The resistance of a liquid to flow; fluidity.
2. The measurement of flow or resistance to shear.
Voids Holes in a coating film. Pinholes.
Watermark on substrate Discoloration of a coating film caused by an accumulation of soluble salts during drying.
Weathering The degree of attack on a coated surface by atmospheric conditions.
Wedging A build-up of coating material at the edge of a substrate. Most common with spray and dip coating processes.
Weeping A form of sagging caused by moisture condensing on the surface of a coating film.
Wetting agent An additive which reduces the surface tension of a coating material, permitting the coating to "wet" the surface of the substrate. Also used to aid in "wetting" pigment particles for improved dispersion in a coating vehicle.
Whiskering See Cobwebbing.
Wrinkle A condition whereby the surface of a coating film is in the process of becoming completely dry while the sub-surface layer is still somewhat fluid, resulting in an absorption of solvent by the surface film and the swelling which forms a wrinkled texture. Also may be caused by uneven oxidation rates of the vehicle in the top and sub-surface layers. It is this phenominon that is used to intentionally produce a wrinkle finish.