Glossary S

SAFETY GLASSES — Safety glasses provide protection against glare, ultraviolet and infrared radiation, in addition to flying debris from glass cutting, poweder spray, and adhesive slpash.

SAGGING PROCESS — Heating glass until it sags and conforms to the shape of the form on which it rests. When heated glass starts to soften, it slumps and sags under its own weight.

SAIRSET–— This technical term refers to a material used in kiln building and to fix chipped or broken molds.

SANDBLASTING — The process of removing glass or imparting a matte finish by blast/bombardment with fine grains of sand that are propelled by compressed air. The purpose is to remove areas of glass from the piece that will either create a design on the surface or that will result in putting a dull finish or a matte finish on the glass.

SAND CASTING — Pouring molten glass into a mold made out of sand.

SATIN — Refers to acid finish or polish; use of hydrofluoric acid to produce a velvety, smooth glass surface. Also refers to hand polished finishes.

SCALLOPING — Refers to decorative ruffles or wavy shape given to the rim of bowls, vases and other glass items during the molding process versus crimping, which is hand done after molding.

SCAVO — A process by which a rougher, matte finish is achieved, by adding a corrosive chemical to the surface of hot glass while it is cooling.

SCORE LINE — A light scratch on the surface of glass when the cutter is pressed against the glass and then drawn or pushed across the surface.

SEEDS — Air bubbles that are trapped in glass during the manufacturing process, usually occuring in groups.

SEEDY GLASS — Also known as seeded glass. Glass in which air bubbles are introduced intentionally into the molten glass prior to forming the sheet and thus entrapped. Typically used used in cabinet doors and windows when some distortion is desired.

SERRATED — Refers to a notched or sawtooth edge on the rim of a glass piece, usually found on cut glass pieces.

SET POINT — A goal temperature of the kiln in any given step of a firing schedule.

SGRAFFITO — A decorative technique, where by the surface is scratched, often to expose another layer of another color.

SHARDS — Pieces of clay or glass broken off from larger glass sheets, or objects. Also referred to as confetti.

SHEARS — A scissor-like tool that is used to cut, trim, and shape hot glass.

SHELF PAPER — Sometimes referred to as "Fire Paper" or "Shelf Release Paper." At 1/32” it is thinner than fiber paper and is used to protect glass from sticking to objects inside the kiln.

SHELF PRIMER — Used to keep glass from sticking to kiln shelf. Sometimes called kiln wash.

SHELLING — Flaking, Peeling. A defect in which glaze falls from the clay body in flakes. It is caused by insufficient bond between glaze and body, usually the result of underfiring.

SHIVERING — A defect in which fired glaze pulls away from the ware taking some of the body with it in the form of slivers. This generally occurs on sharp rims and edges of handles, and is due to improper glaze fit caused by too much compression by the body.

SHORT — Nonplastic clay poor in working qualities.

SHOP — Refers to a glassmaking crew that works together, hand making glass items and glass art pieces.

SHOTGUN ANNEALING — The process of taking glass through different annealing points.

SHRINKAGE — The decrease in size of a clay object due to drying and firing. Dry shrinkage is reversible with the return of water. Kiln firing shrinkage is permanent due to chemical and physical changes clay undergoes when exposed to heat.

SICKNESS — Refers to cloudy stains in glass vessels such as vases, decanters and bottles, caused by chemical reactions inside the vessel when liquid is left in it for a long period; can sometimes be cleaned or may required re-polishing the piece.

SIDE FIRING KILN — The elements have been placed around the sides of the inside of the kiln.

SILICA — Silicon dioxide, a mineral that is the main ingredient in glass. Sand is the most common form used in glassmaking. Also the primary glass forming oxide used in pottery and glaze production. Boron is the other glass forming oxide used although more commonly as a flux than as a glass former due to its low melting point (577oC, 1063 oF). A glass forming oxide must be present in any glaze and as silica’s melting point is 1800oC, 3272 oF, a flux is always present to reduce the melting point to a workable range.

SILVER DEPOSIT or OVERLAY — Complex glassmaking technique that uses electrolysis to deposit a metallic silver design painted on a glass piece with a wash of borax, oxide of lead, sand, nitrate of potash, white arsenic and phosphate of lime mixed in turpentine, the piece is then fired, submerged in an electroplating bath to deposit the silver, and finally buffed and polished.

SLAKE — To moisten dry clay with water.

SLIP — A clay and water mix that has more clay than engobe but is thinner than slurry. A slip is applied to the surface of greenware. Slips are often used for decorative purposes, but they are also used for casting clay in molds. A fluid suspension of clay with and water, with a “cream” like consistency. Most often colored with oxides and painted or poured onto pots for decoration.

SLIPCASTING — Plaster molds are filled with a deflocculated slip; deflocculation reverses the electric charges in the clay particles, which reduces the water content in a slip to that of most plastic clays, around 30% of total weight. A common deflocculant is Sodium Silicate. The plaster absorbs sediment of clay leaving the remaining moisture over the entire interior surface of the mold. The excess slip is drained off and the cast can be removed from the mold soon after. This approach is used widely by industry and some studio potters.

SLIPWARE — A traditional English decorative technique associated with red earthenware and lead glaze. Colored slip is piped onto the leather hard pot much like cake decoration. The most noted exponent of slipware was the 18-century potter “Thomas Toft”; his dishes set a standard that few modern potters can compete with.

SLUMPING — The technique of forming glass using a mold, heat and gravity in a kiln. Glass is shaped by softening and relaxing or falling into a slumping mold or over onto a drapping mold as the kiln heats the glass to a pliable state, referred to as slumping temperature, 1250° F (676° C). The glass then confomrs to the shape of the mold.

SLURRY — A slurry is a thick, viscous slip. It's most commonly used as a sort of glue that helps hold handles or other clay pieces in place when added during the leather-hard stage of the drying process. The term slurry is also applied to glaze mixes.

SOAK — To hold a kiln at one steady temperature for an specific extended period of time.

SOAK TIME — The length of time to hold the temperature of the kiln at a certain set point or temperature before continuing to the next step.

SOFTENING POINT — The point at which glass when heated starts to soften and bend.

SODA-LIME GLASS — Historically, the most common form of glass. It contains three major compounds in varying proportions, but usually silica (about 60—75%), soda (12-18%), and lime (5-12%). Soda-lime glasses are relatively light, and upon heating, they remain plastic and workable over a wide range of temperatures. They lend themselves, therefore, to elaborate manipulative techniques.

SOFFIETTA — A tool used to further inflate a vessel after it has been removed from the blowpipe and attached to the punty. The vessel is reheated, and the conical nozzle of the soffietta is inserted into its mouth so that the aperture is block and air can be blown in through the tube.

SOFT GLASS — A generic name for glass with a relatively high coefficient of and then drawn or pushed across the surface.

SOFT SHOE OR BENCH BRUSH — Used to clean your work surface after cutting glass.

SOLDER — A fusible alloy, usually tin and lead, used to join metallic parts, or the act of applying it. Used to bond metals in both the leaded and copper foil techniques of stained glass work.

SOLUBLE — Capable of being dissolved in water.

SPALL — A shallow rounded flake on a glass object, generally near the rim of a piece.

SPATTER — Similar to Overshot, a technique producing spotted or multi-colored glass with white inner casing and clear outer casing by rolling a gather in tiny particles of glass; Spatter is cased, resulting in a smooth surface, whereas Overshot glass is left rough and uneven.

SPRIGGING — The addition of embossed decorations or low-relief ornamentation to leather-hard or bisque-fired pottery. The sprig is created by pressing a slip or moist clay into a mold.

STAINED GLASS — The common name used to refer to colored or decorative flat glass. Stained glass is most often used in windows, panels, lamps and sun catchers. Many artisans use stained or colored glass in mosaic projects. Stained glass is actually a misnomer the glass is not actually stained but is created by using various oxides and coloring agents. The generic name for decorative windows made of pieces of colored glass fitted into canes and set in iron frames. In addition to glass colored by staining, glaziers use glass colored throughout by metallic oxide, glass colored by flashing, and glass decorated with enamel. The term originally applied to colored or clear flat glass cut to fit an artist’s design, on which details were painted in pigment with a brush. The glass pieces were then heated in a kiln or oven to bond the pigment to the glass surface. This firing makes the painted detail as durable and permanent as the glass itself. Most religious windows from medieval times until this century were executed in this manner, and so the term came to be used first for any architectural application, and then for any design in colored flat glass. It is now universally accepted as a convenient general term to define the art, the craft, and the industry.

STAINS — A suspension of metallic oxides, clays and other materials with water, used to add color to the surface of clay and glaze.

STAIN CRACKS — Fissures in a glass object caused by internal stress from inadequate annealing and/or accidental thermal shock.

STACKING — The layering of sheets of glass to create patterns or images.

STAINED GLASS FUSING — Fusing glass and using the pieces in a stained glass project.

STAINLESS STEEL MOLDS — Made for glass fusing, or metal bowls and other objects made out of stainless steel.

STONE — Small impurities in glass, such as a particle of furnace material.

STONEWARE — Highly vitrified ceramics fired to above 1200oC, 2192 oF. Most of the silica in a fired stoneware body is melted into a glassy matrix and the resulting body is of high density and usually has a water absorption rate of less than 1%. Stoneware is a non-porous, high-fire clay that's harder and stronger than earthenware. Stoneware does not require glazing in order to be waterproof. Stoneware contains more clay than porcelain and is opaque rather than translucent.

STRAIN POINT — The lowest annealing temperature. Below the strain point any stress in glass is permanent.

STREAKY GLASS —Two or more cathedral glasses mixed together to create a multi-colored glass sheet. Some use this term also to describe Mixed Opalescent glass.

STRESS — A force creating tension and compression within glass that could cause unwanted breakage. Internal stress can be caused by poor annealing or fusing of incompatible glass. Tension in glass that could cause it to break.

STRIKER OR STRIKING COLOR — A glass or frit that will actually change from one color to another when a specified temperature is reached. They appear to be light or white before they are fired and change color when the striking temperature is reached.

STRIKING — The process of reheating glass after it has cooled, in order to develop the color or the opacifying agent which appears only within a limited range of temperatures.

STRINGER — A very thin, spagetti like rod of colored glass, approximately 1.5mm in diameter that is used as a decorative element in fusing and hot glass work.

STUDIO GLASS — A term used to describe unique or limited-edition glass objects that were designed and created in a studio instead of a factory.

STUDIO GLASS MOVEMENT — Art movement that began in the United States in the 1960s, characterized by the proliferation of glass artists who were not affiliated with factories, but worked with hot glass in their own private studios. The emergence of independent glass artists was made possible by the development of small furnaces and easy-to-melt glass.

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