Glass Glossary:
Terminology for the Glass Collector*

Compiled by Ron Fox

Acid etched � process by which acid is used to etch part or all of a glass surface.

Agate glass � glass that has a marble-like appearance (see Lithylin Glass).

Alabaster glass � see Milk glass and Opal glass.

Alkali � a soluble salt that is one of the essential ingredients in making glass, serving as a flux to reduce the fusion point of the silica; alkali is supplied in borax, soda or potash.

Amalgam � an alloy of mercury and another metal; used with gold for gilding glass.

Annealing � the process of reheating glass and allowing it to cool at a slow, uniform rate; properly done, annealing removes the stress within the glass.

Antimony � a metallic oxide used to produce yellow coloring of glass.

Arsenic � an oxide of arsenic used to improve color, transparency, and brilliance, often used when producing opaque white glass or opaline.

Art glass � a style of glass that relies on color, texture, and form for its visual appeal.

Artistic glass � a style of glass that uses surface decoration techniques such as engraving, cutting, or enameling.

Ashes � a residue of burnt materials from marine plants such as beechwood, ferns, or bone; used as an alkali in glassmaking.

At-the-fire � reheating a glass object during its formation to permit further blowing for the purpose of enlarging or manipulating its shape.

Amber � a yellow or yellowish-brown transparent glass coloring.

Aventurine � internal decoration process in which silver, gold, or other metallic flakes are suspended within the glass.

Batch � the granulated recipe of ingredients used in the process of making glass.

Beading � the process of attaching an intermittent series of glass beads to decorate a glass surface.

Biedermeier � a German style of decoration which derived its name from a drawing by Ludwig Eichrodt in a German journal featuring two smug characters called Biedermann and Bummelmeier; the term Biedermeier came to be applied to the style current in 1820-1840.

Blank � undecorated glass usually made to have a cut, engraved, or acid etched decoration added.

Blow pipe � A hollow metal rod on which molten glass is gathered at one end to be blown into and shaped.

Blowing � the process of inflating the glass gathering by means of a blow pipe.

Bohemian glass � a style of glass, usually wheel cut, originating from the Bohemian glass houses; Bohemia became part of Czechoslovakia in 1918.

Bone ash � ashes of bones used as a flux in the glass-making process that produces Opaline glass.

Bone glass � see Milk glass.

Cameo glass � two or more layers of glass where the top layer is cut to reveal relief cuttings in that top layer and the under-layer in other areas.

Cased glass � glassware made of two or more layers of different colored glass. The process involves first making an outer casing by blowing a gather, knocking off one end, and opening the piece to form a cuplike shell. This shell is then placed in a metal mold and a second, different colored gather is blown into it. This combined piece is taken from the mold and reheated to fuse the two layers together. The outer layer is thick, which distinguishes it from the thin outer layer of flashed glass. This term is also improperly used in place of flashed or overlay to imply one layer of glass over another.

Chair � a team of workers combining their efforts to complete a work of glass.

Chromium � a metallic agent used in glass to produce a yellowish�green color.

Clear glass � transparent glass, devoid of any color.

Cobalt � a metallic agent used in glass to produce dark and light shades of blue. Cobalt oxide is mixed with molten glass, cooled, and then ground into powder to produce a coloring agent for glass enamel. This enamel is also used in pottery and porcelain glazes.

Cold painting � lacquer colors or oil paint applied to glass, porcelain, or stoneware, but not fired on.

Color etching (Cut To Clear) � the process of applying a thin, flashing of colored glass over clear glass, then etching the surface so that a clear glass design shows.

Copper oxide � a metallic agent used in glass to produce turquoise blue or green.

Coralene � the application of tightly spaced beads onto a glass surface to give the decoration a coral�like appearance and texture.

Cranberry � transparent glass with a pinkish-red coloring.

Crizzling � a flaw in the batch that causes the surface of the glass to become crazed. This improper balance of ingredients sometimes occurs because of too much alkali and can also result in the glass losing its transparency.

Crystal � a clear, colorless glass cut or faceted to resemble Rock Crystal; this term is used loosely to describe all fine clear glass.

Cullet � glass broken during the glass-making process and saved to be reused.

Cut glass � glassware that is decorated with facets, grooves, and depressions made by cutting with rotating wheels of iron or stone; once the pattern is cut, it needs to be polished.

Cutting wheel � a stone or iron wheel used to decorate cut glass; the rotating wheel is used to cut designs into the glass body.

Cut-to-clear � See Color etching.

Decolorizing agent � a mineral used to counteract the greenish or brownish color in glass caused by iron particles in the silica (sand) or from iron in other ingredients in the batch.

Diamond cutting � scenes scratched onto the glass surface using the point of a diamond or a sharp metal tool.

Diminishing lenses (Reducers) � polished concave circular lenses that concentrate light and reduce the image; usually found on Bohemian pieces on the side opposite from the central scene.

Enamel � a combination of frit, metallic oxides and oil painted onto glass that fuses to the glass surface when fired.

Enamel firing � enamel colors are mixed with a flux to lower the fusing point below that of the glass object; the lower temperature is necessary to fuse the enameling to the glass object without damaging its form.

Enamel overlay � the process by which a glass body is enameled with a heavy layer of one color giving the appearance of a glass overlay; this enameling can be cut through to reveal the layer underneath.

Enameled line gilding � a decorative technique whereby enameled lines are painted and fired onto a glass body to form the outline of a design. After cooling, the entire design is painted with gold and fired on. This technique produces raised outlines and gives the decoration a three-dimensional effect.

Faceted glass � glass containing flat surfaces ground onto the body. A prism would be considered a faceted decoration.

Filigree glass � glass with internal decoration of threads (generally twisted) imbedded within the glass.

Fire worked � shaping and manipulation of glass with heat.

Firing � the process of heating the batch in order to fuse the ingredients into glass; also denotes reheating unfinished glassware while it is being worked, or reheating glass to fix enameling or gilding.

Flashing � applying a thin layer of glass to the body of a glass object by dipping the piece into molten glass of a different color; this outer layer can be cut or scratched through to reveal the body color underneath.

Flux � an ingredient such as borax, potash or soda which, when added to the batch of glass, helps to lower the fusing temperature of the silica.

Folded foot � a foot with the outer rim folded back and fused to the glass, making a double thickness at the edge, similar to a hem on a cloth garment.

Free hand blown � See Hand blown glass.

Frit � previously made glass, ground into a powder and mixed with oxides and oil to give enamel its glass base; this ingredient is important in fusing colors onto the glass body.

Furnace � a round brick structure in the blowing room built for the blowing of glass; in early times it was fueled by wood, later by coal, and now by gas.

Gaffer � the glass craftsman presiding over the chair.

Gathering � a blob of molten glass attached to the end of a blow pipe or pontil rod.

Gilding � the process of decorating glass by firing on gold leaf.

Glass blower�s bench � a chair with iron arms which allows the blower to roll the blow pipe back and forth spinning molten glass; the centrifugal force of the spinning maintains the shape of the glass while it is being worked.

Glass blower�s soap � a term used by glass blowers for the decolorizing agent.

GLASS POT � clay pot in which the glass batch is melted within the furnace.

Glass relief � precast figural glass forms such as acorns, bees, birds, fish, etc. that are applied to the glass body; they are usually enamel decorated.

Ground pontil � ground and polished pontil mark leaving a hollow, smooth depression in the center of the underside of the base.

Hand blown glass � the process of taking a gathering of molten glass on the end of a blow pipe and working it into a ball on the marver so it can be blown and shaped with hand tools.

Highlighted transfer enamel � the use of the Transfer Enamel process with the addition of minor hand painting (see Transfer enamel).

Historismus glass � a German term referring to late 19th century glass made in the style of 17th century and earlier periods.

Hydrofluoric acid � a colorless, highly corrosive acid that attacks all silicates; used to etch the surfaces of glass and porcelain.

Hyalith � a dense, totally opaque glass of either wax-seal red or black that is usually facet cut and/or gilded.

Glass steins: ruby stained, c. 1850; blue overlay, intaglio cut, c. 1850; white on green overlay, c. 1880; blue opaline, c. 1850

Ice glass � an effect caused by submerging molten glass in cold water, causing the entire surface to crack; the glass is then reheated and the cracks are smoothed over; also known as Crackled glass.

Intaglio � deep hollowed-out cutting or engraving.

Internal decoration � an apparent decoration inside glass, created by mixing, inserting, or other forms of manipulation; examples are Aventurine, Filigree, and Sulphides; not to be confused with surface decorations.

Iridescent glass � glass that contains a rainbow-like coloring on its surface, similar to the effect of oil on water; caused by either weathering or lustre painting.

Lampwork � lightweight manipulated glass made and worked over an open flame or lamp, such as small glass figurines made at fairs.

Lead glass � glass with a high lead content in the batch, which lowers the melting point and softens it for cutting; Lead Crystal was also used during the brilliant period of cut glass.

Lehr � a 20th century apparatus that performed the annealing process.

Lithyalin � process used in the early 19th century which gave the surface of the glass a marble-like appearance.

Lustre painting � painting on the surface of glass with metallic oxide pigments to produce a metallic, iridescent effect.

Manganese oxide � a metallic oxide used to color glass amethyst or purple hues; mixed with cobalt it produces black hyalith glass; also used as a decolorizing agent.

Marble glass � see Lithylin.

Marver � iron or marble table where molten glass gathered onto the end of the blow pipe is rolled into a symmetrical mass so it can be blown.

Mary Gregory style � a style of enameling on glass done only in white and generally picturing Victorian children.

Metal � a term glassmakers often use when referring to glass.

Metallic oxides � used as pigments to color glass and to make enamel colors used to decorate glass surfaces.

Milk glass � an opaque glass with the appearance of white porcelain; its opacity and color are due to the addition of tin oxide, which is also used to give faience its opaque white glaze covering.

Mliiifiore glass � glass containing an internal decoration whereby a cross section, or slice, of a grouping of different colored glass rods is imbedded into transparent glass.

Mold blown � molten glass that is blown into metal or wood molds, eliminating some or all shaping with hand tools; the glass takes on the shape of the mold into which it is blown.

Molten glass � glass in a melted state after the ingredients have been fused at a high temperature, liquefying the batch. It is then allowed to cool until it is plastic and shapeable. It is sticky and will adhere to an iron blow pipe or other glass object already heat-softened.

Needle scratched � lines scratched through stains, enamel, or gilding using a sharp, pin-like tool.

Opal � see Opaline.

Opaline � a dense translucent glass that derives its diffused nature from the addition of bone ash, and is colored using metallic oxides, usually in pastel hues.

Opaque enamel � enamel that prevents the glass undercolor from showing through.

Opaque glass � solid colored glass that allows little or no light to pass through.

Overlay � covering one color of glass with one or more layers of other colors.

Painting � the process by which enamel is applied to glass.

Parison � the gather of hot glass after it has been partly or wholly inflated by the glass blower.

Pincers � a plyer-like tool used for inserting pinched decorations on handles, rims, etc.

Plastic � glass in the molten state, in which it is easily modeled and shaped.

Polished cut � polishing the matte surface of intaglio engraved glass using soft disks or brushes made of leather or cork, enhancing the effect of the cut.

Polishing � the process of giving glass a smooth, brilliant surface after it has been cut or engraved; first it is polished with a fine-grained stone wheel, then with a finer wheel made of lead, wood or cork.

Pontil mark � a rough mark in the center of the base of a blown glass object where the pontil rod was attached; usually ground and polished from the 1860s onward.

Pontil rod � a solid iron rod to which a partly made glass object is transferred from the blow pipe; here the final shaping, finishing of the neck, and attachment of handles or other applied glass takes place. A small gathering attaches the object to this rod.

Pressed glass � made by pressing molten glass into a mold to form its shape.

Prism � glass with multiple flat facets that have been stone wheel cut and polished, similar to facets found on diamonds.

Prunts � dabs or blobs of molten glass applied to a glass body while in the plastic state.

Punty � see Pontil.

Reducers � see Diminishing lens.

Relief enamal � a raised decoration achieved by applying heavy or multiple layers of enamel; also refers to the application of porcelain relief to the glass body, attaching it with a low-fired adhesive and then encasing it with an enameled decoration.

Relief gilding � a decorative technique where a thick enamel design is painted onto glass and then fired in a kiln; after cooling, it is overcoated with gold and refired, resulting in an overall gold relief design.

Resist � the wax preparation used to protect the glass surface from the acid used during the Acid Etching process; surfaces not covered with the resist are etched by the acid (see Acid etching).

Rock enamelL � two possible meanings: (1) a cut and faceted clear quartz stone; (2) a style of 19th century glass cut to resemble clear quartz stone.

Rigaree � glass bands or ribs applied as decoration while in the molten state.

Roemer � a goblet form with a wide foot that gradually tapers upwards and diminishes in size until it reaches the under side of the bowl.

Ruby � glass with a blood-red coloring, achieved by adding copper, gold, or selenium.

Sand � the main silica ingredient in the manufacture of glass.

Sand blasting � sand particles directed at the glass surface at high velocity to etch a design.

Schwartzlot � a German term for black enamel that was used on glass from 1650-1750, most often by Hausmalers (freelance painters) outside the factories.

Shears � a scissor-like tool used to cut glass while in the molten state.

Silica � one of the essential ingredients used in making glass; a mineral, the most common form being sand from the seashore or inland beds.

Silver sulphide � produces a deep yellow glass stain.

Sode � sodium carbonate; an alkali ingredient used as flux in glass making.

Stained � glass on which oxides are brushed and then fired, giving a consistent overall color to the surface; this stain can be cut through to reveal the under color.

Stippling � the process of decorating a glass surface by striking it with a diamond or hardened steel point leaving small, shallow dots; the proximity of these dots create the image.

Sulphides � an internal decoration which imbedded a porcelain-like figure within the glass; occasionally enameling on gold foil was also imbedded.

Threading � the process of spinning glass threads onto already shaped bodies while in the molten state.

Tin oxide � metallic ingredient used to give milk glass its opaque, porcelain-like white appearance; also used to make the opaque white glaze covering on faience.

Transfer enamel � process in which an enameled decoration is printed onto paper which is then applied to the glass body and fired on, burning off the paper and leaving the transferred print in place; this process eliminated the need for hand-decoration.

Translucent glass � glass that allows only a portion of light to pass through, making objects seen through it appear unclear; opaline is in this category.

Transparent glass � glass that allows light to pass through without diffusion, allowing objects to be seen through it clearly.

Transparent enamel � enamel that allows light to pass through it.

Uranium glass � glass made with uranium in the batch, giving it either a yellowish-green (Annagrun) or greenish-yellow (Annagelb) color; gives off a fluorescent glow when light shines on it. Also known as Vaseline Glass.

Vaseline glass � see Uranium glass.

Venetian glass � a style of glass made in Venice from the 13th century to the present time.

Weathering � the natural process of irridising the surface of ancient glass which results from being buried for hundreds of years.

Wheel engraving � surface cutting done by using wheels of different sizes to produce intricate scenes such as portraits, animals, buildings, etc.


Reference: An Illustrated Dictionary of Glass, by Harold Newman


*Reprinted from The Beer Stein Journal, August 1994, by permission from Gary Kirsner Auctions.