Decorative Glass Terms

ABRASION: A wearing, grinding or rubbing away by friction.

ABRASION RESISTANCE: The inherent ability of a coating or substrate to resist degradation or destruction by friction.

ACUITY: Sharpness.

ADHESION INTERCOAT: The ability of coatings to adhere 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.

ARTWORK: A design developed primarily for reproduction.

BLEEDING: Migration of color from the coating film onto or into a surface with which it comes in contact.

BLEMISH: A noticeable imperfection.

BLISTER: A profusion of bubbles in a coating film that form during the heat treating process and remain after the film solidifies. Surface disruption in extreme cases.  Frequently accompanied by a slight color change. Carbon entrapment in ceramic coatings. Ceramic coating can easily be scratched with knife blade or other hard object.

BLUR: Smear, image lacks sharpness, out of focus.

CERAMIC ENAMEL: An inorganic, essentially non-metallic coating, to be fused to a substrate at or above red heat.  Consists primarily of a glass frit and inorganic pigments.  May be mixed with an organic vehicle.

CHECKING: Fine hairline cracks in a dried coating film which begin at the surface and progress downward.

COLOR VARIATION: Noticeable color differences over the coated area on the same piece.

CRATER: 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.

DECAL, DECALCOMANIA: A specially prepared paper on which designs have been printed with ceramic enamels for the purpose of being later transferred to glass.

DEVITRIFICATION: A change in a ceramic coating resulting in a loss of gloss due to crystallization. Usually caused by extreme overfire.

DIMPLE: A shallow depression in a coating film. Related to Craters.

FISHEYE: Defect in coating film, generally a circular depression, usually resulting from contamination of the substrate surface, the coating flows away from the contaminant.

FIT: The stress relationship between the fired ceramic enamel and the glass substrate to which it has been applied.

FLOOD COAT: The spreading of a layer of coating material over the image area of a printing screen without actually printing. This serves a dual purpose:

1) To keep the image area wet so as to reduce any tendency to clog;

2) To provide an adequate supply of coating material for the printing stroke;

3) Essentially full coverage of a one color coating.

FRIT: A form of low melting glass which forms the permanent vehicle of glass enamels.

GHOST: An image of the printed pattern which extends beyond the boundary of the stencil.

GLOSS: The degree of shine or luster on the surface of a ceramic enamel or ink.

HALF-TONE: A type of printing in which dark and light details are represented by dots of varying sizes in relation to the tones or shades they must portray.

HICKEY: An impression in a screen printed coating caused by contamination; i.e. dirt, lint, hardened specks of color, etc.

IRIDESCENCE: A surface rainbow effect, similar to an oil-on-water appearance. Normally caused by atmospheric moisture or alkali attack.

MATTE: Without luster or gloss; dull.

MESH: 
1) The woven material that supports the pattern.
2) The term that designates the number of openings per linear inch or centimeter.

MOIRE: 
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;
3) An optical phenomenon or illusion caused by close proximity of similar patterns.

MOTTLE: A blotchy appearance in a coating film.

NEGATIVE: A negative image mode in photographic film dark areas of subject are clear on film, light areas of subject are black/opaque.

OPACITY: The relative capacity of a coating material to obstruct the transmission of 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.

PARALLELISM: 
1) The degree to which two surfaces (or lines) maintain equidistance apart over the entire length. 
2) The degree to which a mounted screen and the substrate or printing table are equally spaced.

PATTERN: An artistically or mechanically produced design for screen printing.

PINHOLES: Tiny, transparent openings in a coating film that can be attributed in 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, Fisheyes

POSITIVE: A positive image made in photographic film, dark areas of subject are black/opaque on film, light areas of subject are clear.

QUALITY: A relative term describing the degree of excellence of a product, process, and/or service as required by specifications.

REGISTRATION: The ability to print one or more colors and maintain pattern location on the substrate and alignment of each color to all others.

SATIN: A smooth, lustrous texture.

SAWTOOTH: Uneven edge definition in a screen printed design caused by inadequate thickness of emulsion or insufficient exposure of the emulsion which results in the emulsion, during washout operations, to break free of an entire mesh opening, following the contour of the mesh instead of the contour of the image. Most obvious with coarser meshes where the pattern steps over a thread.

SCALLOP: A condition in which the edges of the coated area pull back resulting in a scallop-like appearance.

SCREEN: An assembly of stretched screen mesh fabric on a rigid frame with a stencil attached, ready for printing.

SCREEN SNAP: A defect in a printed film, usually in the shape of an arch that appears at the trailing edge of the print stroke. Caused by the sudden release of the screen from the substrate before the peeling action is complete.

SCUFF: An abrasion or full area on a glass substrate usually caused by furnace rolls or contact with other furnace parts during heat treating cycle.

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 adequately wash out the emulsion.

SHADOW: See Ghost.

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 stoke.

SMUDGE: See Smear.

SNAP-OFF: The distance between the mounted screen and the surface of the substrate to be printed. Also called “off-contact.”

SQUEEGEE: The tool or table used to force the printing ink through the screen and onto the substrate.

STREAK: Elongated defects.

SUBSTRATE: The item or material to be printed.

SULFIDE STAIN: A metallic-appearing gray-like scum on a fired ceramic surface which develops during storage of the decorated product.  It is caused by sulphur-containing packaging or atmospheric attack.

TRANSLUENT: The quality of a film or substrate that determines the transmission or diffusion of light.

VISCOSITY: The term used to designate the degree of fluidity of a coating material. Affects screening quality.

VOIDS: Holes or openings in a coating film.

Disclaimer

The information in this Glossary is to the best knowledge of the Consolidated Glass Corporation (CGC) considered to be true and accurate, but all recommendations or suggestions are made without guarantee. Since the conditions of use are beyond the control of the Consolidated Glass Corporation (CGC), Consolidated disclaims any liability for loss or damage suffered from the uses of data and/or suggestions and recommendations contained in this Glossary.