F

Figured Glass - Also known as "patterned" or "ornamental" glass, figured glass is generally produced by the rolling process. The surfaces of the rollers used carry the pattern or design to be "imprinted" in the glass as it passes between them. The process gives the glass a texture surface on one side or both sides. The surface finish may be both decorative and functional. Apart from the huge variety of patterns possible, figured glass can also offer light dispersion and glare reduction characteristics.

Filigrana - The generic name for colored glass encased by clear glass that has been pulled into a piece of cane. The filigrana style originated at Murano, Italy in the 16th century and spread through Europe.

Finished - The process of completing the forming or decorating of an object. Finishing may take the form of manipulating the object into its final shape while it is hot, of cracking off prior to annealing, or of grinding, cutting or polishing.

Finisher - The glass worker (generally the Gaffer) that puts the finishing touches on the glass before it goes into the Annealing Oven.

Fire-Resisting Glass - Flat glass with a wire inlay that helps retard shattering in the event of fire and thus delays the spread of smoke and flames. Such glazing is classified either as class G (which resists fire and prevents the spread of smoke and flames for a specific period of time) or class F (which has the characteristics of class G but also impedes the spreading of radiant heat for specific periods). New developments include pre-stressed wire-free borosilicate glass and double-glazing with the inner space filled with an intumescent material which acts as a heat shield.

Firing - The process of bringing a glass furnace up to its operational temperature and then maintaining the temperature.

Flameworking - The technique of forming objects from rods and tubes of glass that, when heated in a flame (gas-fueled torches), become soft and can be manipulated into the desired shape.

Flashing - Quickly placing the working glass into the Glory Hole to reheat the entire piece to assure that the glass will be pliable and keeping it safe from cracking.

Flat Glass - AII types of glass (rolled, float, plate, etc.) produced in a flat form, regardless of the method of production. Float process: A method for the production of high-quality sheet glass whereby a ribbon of molten is fed across a bath of heated liquid, usually molten tin, in a carefully controlled atmosphere. The UK firm Pilkington Brothers developed the process.

Flint - A glass color or lack of color. Flint is perfectly clear transparent glass, like window glass, used for all types of containers.

Fluted - The vertical lines, grooves or designs in the glass.

Founding - Heating the glass to a proper usable temperature. The initial phase of melting batch. The material must be heated to a temperature of about 2450 degrees Fahrenheit. This is followed by a maturing period, during which the molten glass cools to a working temperature of about 2000 degrees Fahrenheit.

Frit - Clear or opaque color that is crushed and graded to specific sizes. Batch material that is melted with other materials and then ground into powder form before being added to the batch. Lead oxide, which can produce a harmful dust, may be melted with silica, for example, and then ground down as a lead silicate.

Fusing - (1) The process of rounding or melting the batch; (2) healing pieces of glass in a kiln or furnace until they bond; (3) heating enameled glasses until the enamel bonds with the surface of the object.

Fusing Glass-to-Glass - Glasses of different compositions can be fused together for decorative purposes and also in the sealing of electric, medical and industrial components. The fusion temperature for soda-lime glasses is generally between 760 and 820C. Particular attention must be paid to the thermal expansion coefficients of different glass types.