ACID ETCHING — Process of cutting a design into glass using acid as the cutting agent. The vessel is then exposed to hydrofluoric acid or acid fumes, which etch any unprotected surface areas, thus leaving a frosted design when the protective layer or resist is removed.
ACID FINISH — Matte finish produced by exposing surface of a glass piece to acid fumes during finishing or, in some cases, with a mechanical grinding wheel (also see Satin).
AIR SIDE — A term associated with window glass, properly known as float glass. During the manufacturing process of float glass, an invisible residue of tin is left on one side of the glass. The opposite of the tin side is the air side.
ANNEALING — The process of slow cooling heated glass through the annealing zone to prevent the presence of internal stress. The appropriate cooling curve varies with glass type and formed shape, especially thickness This is done between the cooling of the glass from 1000° degrees Fahrenheit down to 600°degrees Fahrenheit. Proper annealing is critical in glassmaking, as glass that is allowed to cool too quickly will break as it cools or will be highly strained when it reaches room temperature and liable to break easily. If glass is not properly annealed, it is likely to break during the cooling phase or at a later date.
ANNEALING POINT — The most efficient temperature at which to anneal a particular glass. Usually found at the upper end of the annealing range. It is the stress-relief point during the cooling phase of glass fusing.
ANNEALING ZONE — The temperature range starting at the softening point and ending at the strain point. Generally located between 1100F and 600F (593C and 316C), depending on the chemical makeup of the particular glass.
BAS-RELIEF — A decorative method in pottery and sculpture in which figures or forms project only slightly from the surrounding surface. In bas relief or low relief, figures are not undercut to become three-dimensional.
BATCH — The mix of granular raw materials put into the melting furnace to produce glass. This includes silica, soda, potash, and lime. Various colorants are added to the batch in smaller quantities.
BEAD RELEASE — Used to coat mandrels when making a hole in glass.
BENCH — The bench is the heart of the hot shop work station. It consists of two parallel rails (to roll the blowpipes on), a tool table, and a seat where the artist sits and manipulates the glass.
BENT — Another term for slumped glass. When glass has been heated in a kiln so that it softens and slumps into or sags over an object. The finished item takes the shape of the mold.
BEVEL — Cold glass (usually clear, thick plate) with edges that have been ground and polished to an angle other than 90 degrees. Transmitted light is refracted and a prism-like effect results. Bevels are available in a variety of sizes, shapes and geometric configurations (called "clusters") for incorporation into leaded glass work.
BILLET — A glass ingot, similar to a dalle, used in glass casting
BISQUE — A fired (vitreous) piece of unglazed clay. The first firing a pot undergoes to prepare it for glazing. This is done at a higher temperature than the subsequent glaze firing
BISQUEWARE — Is unglazed, air-dried (aka bone dry) greenware that has been bisque fired, or fired once, to a temperature preceding vitrification. Bisque can also be glazed and then fired again.
BLANK — A solid bottom layer of glass upon which other pieces of glass are positioned prior to fusing. The bottom layer of glass.
BLOWING — The act of inflating a hot gather of glass through a blowpipe.
BOTTLE CUTTER — A tool used to cut glass bottles.
BOROSILICATE GLASS — A type of glass that is dense, harder than soda or lead glass, and has a low co-efficiency of expansion (which allows it to withstand sudden changes in temperature). It is often used for sculpture flameworking because it passes from the molten to rigid state quickly.
BREAK — When glass separates and becomes two or more pieces. Unlike “smashing glass” this is not a bad thing in glass work (it is a desired result in glass cutting.)
BREAKING PLIERS — Used like your hands to break off glass at the score line.
BRITTLE ZONE — Also referred to as the cold zone. This is from room temperature to about 900 degrees Fahrenheit.
BLOWPIPE — An iron or steel tube, usually about five feet long, that is used for blowing glass. Blowpipes have a mouthpiece at one end and are usually flared at the other end with a shape that helps retain the gather.
BURN OUT — The process of pre-firing a mold or material in a vented kiln to remove, with heat, any unwanted contaminants.