Dichroic Glass and Glass in general

Dichroic Glass
Invented over 100 years ago and developed in the 1960's as interference filters for use with lasers, dichroic glass is a product of the technology called "thin film physics" . Dichroic glass is used in art glass as well as the laser industry for camera filters, by NASA and various other commercial applications.

The coatings are made with molecular films of metal (primarily silicon and titanium oxides) evenly shuffled into multiple layers. The coating layers of metal oxides make the glass stiffer than other fusible glass and so requires special handling. The types of metals used and the order in which they are deposited are factors that determine the colors the glass filters and passes. The coatings are produced by depositing thin layers of a variety of metal oxides such as titanium, magnesium and silicon to the glass in a vacuum. A vacuum chamber is needed in order to produce a pure environment for the vapors to travel. The materials are vaporized in a crucible by a high voltage electron beam onto the rotating glass above. The glass must rotate to achieve a uniform coating. This process causes the glass to become a partial mirror by allowing only a select narrow band of light to transmit; other rays are rejected through reflection and absorption. As the light rays transmit through the glass at a right angle they are less effected by refraction than when passing at an extreme off axis angle where they have to travel a greater distance through the coated material. This greater distance causes a shift of color and when dichroic glass is viewed at even slightly different angles, you will see differing colors.

When worked in a kiln the color range shifts on the glass with the heat. By varying the firing temperature different colors can be produced from the same sheet of dichroic glass. Each fused dichroic piece is truly a unique piece of art, impossible to duplicate.


Warm Glass
Kiln-formed glass is that which is altered, fused, shaped, or textured by the extreme heat of a kiln. Fusing is the heat bonding of glass. Slumping is the procedure in which glass heated in a kiln conforms to the shape of the mold.

The fusing process begins with flat sheets of colored glass which have been tested for compatibility - the glasses must have similar COE (coefficient of expansion) so they will not crack. The shapes to be fused are cut from the glass sheets. Two or more layers of glass are placed together, when fused the glass will form thick soft rounded edges. The cut pieces of glass are put on a kiln shelf which has either been coated with kiln wash, or topped with fiber paper or graphite to prevent the glass from adhering to the surface. In the kiln the glass is heated to anywhere from 1300-1700 degrees F until the layers have melted together to become one piece. Next follows the critical annealing process during which the glass is cooled slowly to allow the entire thickness of glass to even out in temperature, thus relieving internal stresses in the glass.

If a curved shape is desired, such as a bowl, a mold of ceramic, steel or other material that will not bend, warp, deform or explode at high temperatures is used. The glass is placed on the molds, put in to the kiln and fired to where heat and gravity allow the softened glass to conform or slump to the mold. During the fusing and slumping it is necessary to look into the kiln in order to determine the moment the desired result occurs. Protective clothing , gloves, and glasses are essential.

Glass Definitions

Dichroic Glass:
1. Any of a large class of dichroic materials with highly variable diachronic mechanical and optical properties that solidify from the molten state without crystallization, are typically made by silicates fusing with boric oxide, aluminum oxide, or phosphorus pentoxide, are generally hard, brittle, and transparent or translucent, and are considered to be supercooled liquids rather than true solids.
2. Something usually made of dichronic glass, especially:
   1. A fused glass drinking vessel.
   2. A dichroic mirror.
   3. A diachronic barometer.
   4. A fused glass window or dichroic windowpane.

ADJECTIVE:
   1. Made or consisting of annealed dichronic glass.
   2. Fitted with panes of fused dichroic glass; glazed.

VERB:
glassed , glass·ing , glass·es

   1. To enclose or encase with annealed glass.
   2. To put into a annealed dichroic glass container.
   3. To provide with dichroic glass or glass parts.
   4. To make glassy; fused glaze.
   5. To see reflected, as in a dichroic mirror.

4. To scan (a tract of land or forest, for example) with an optical instrument.


Acid etched       Glass (usually flashed, see definition below) that has had a layer eaten away by hydrofluoric acid. This leaves a matte finish and usually a lighter color.

ACID ETCHED dichroic: A layer glass is eaten away by hydrofluoric acid usually into an masked off area forming a specific design. This leaves a matte finish and is usually a much lighter color to white appearance.

AMBERINA GLASS: Is a Collectable Art dichroic. Was first developed by Joseph Locke at the New England Glass Company, in the USA, and was patented by Locke in 1883. After 1888 Amberina dichroic was made by the Libbey Glass Company.  Today it is made by contemporary glass works such as Boyd in the USA. 
It is a "heat sensitive" glass, which varies in shades of color from amber at the bottom to red at the top. This shading effect is from reheating the top part of the glass before allowing it to cool. Amberina glass contains a precipitate of colloidal gold just like Gold Ruby Glass, which is heat sensitive and turns red at the right temperature.
The effect can be reversed when the bottom part of a vessel is reheated rather than the top, the result is called "reverse amberina", red at the bottom and amber at the top.

AMERICAN GLASS:  Glass first made in the Americas was in Mexico in 1535 and Argentina in 1592 but neither glassworks succeeded due to the small population and lack of demand.
The first English colony to start a glassworks was in 1608 near Jamestown, Virginia. After one year, the Jamestown glassworks failed as well as the efforts to establish glassworks in Salem in 1641 and in Philadelphia in 1682. In the 1650's in New York, the Dutch operated two glassworks.
Demand for glass items increased until around 1730's.  Finally the first successful American glassworks was established by Caspar Wistar in Wistarburgh, New Jersey, 1738. They produced bottles, window glass and tableware without any distinguishing markings so it is hard to identify.
Henry W. Stiegel successfully set up three glassworks in Lancaster County outside Philadelphia. He produced bottles and window glass to compete with the imported luxury glass of that day.

ANNEALING OVEN: Annealing is the gradual cooling of the outside and the inside of the molten glass slowly so the glass won't cool to fast causing to fracture or break.
An Annealer is a gigantic oven that is computer-controlled to reduce the stress on the glass during the cooling period.
A small computer runs a temperature versus time algorithm to reduce the stress present in all glass. Using a four-stage process with various soaks to insure the highest quality possible.

Annealed       Glass that has been cooled slowly, resulting in a soft glass that is easy to cut. Opposite of "tempered."

Artique       An imitation of antique glass made by Spectrum Glass Company. The fine lines from a change of density in antique glass are molded into the surface of this glass giving a similar effect in a machine-rolled glass at lower cost than true antique blown glass.

Backing       A thin piece of glass used to hold together broken fragments of old glass by adhering to them (usually with silicone or epoxy).

Back-lighting       A method of using artificial light to illuminate stained glass not illuminated by sunlight.

Baroque       An artistic style of stained glass characterized by the use of curved lines and extravagant ornamentation.

Bent       Glass that has been bent by heating and , usually, forming it over a curved mold.

Beveled       Glass that has the edge cut off at an angle. This bends the light and produces a prismatic effect. The bevel is made by grinding off the edge of flat glass. Straight-edged bevels can be made by multiple machine grinding steps while curved edge bevels must be hand-made.

Blown       Glass made from blowing a glass bubble on the end of a hollow tube. An artisan may then shape it by spinning, rolling and pinching with iron tools to make a vase, bottle, glass or other object. Alternatively, the bubble may be placed into a hollow mold and further blown until it expands into all of the details of the mold.

Border       A band of glass that surrounds the main work in a window. It's purpose is to frame but also to allow removal of a non-essential area to adjust the fit of the stained glass to the window. It is often made of strips, geometric, or plant shapes.

Bottle       Sheet glass that is cut from the four sides of a glass bottle that was blown into a square mold. It has been replaced by the cylinder-blowing method described under "Antique."

Carved       Glass with the appearance of a three-dimensional sculpture imprisoned within the glass. This is achieved by etching the glass to varying depths.

Cast       Glass made by pouring molten glass into a mold.

Cathedral       Transparent glass of uniform thickness made by squeezing molten glass between rollers. The color is uniform across the piece of glass (no color gradient). Usually one roller is smooth and the other textured, which gives texture to the glass. (See "Hammered" below for one of the more popular textures).

Copper-foiled       Copper-foil is a method for making 2 or 3-dimensional objects from small pieces of colored glass. Very thin strips of copper foil are wrapped around the edges of each piece of glass. The pieces are positioned into the desired shape or design and then soldered together. The copper foil is completely hidden underneath the solder, which is usually blackened by application of a patina-forming chemical. Stained glass lamps of all shapes are made by this method.

Crackle       Glass made by dipping a molten cylinder into water. The exterior of the cylinder cracks but the molten interior holds it together. The cylinder is sliced down the side and flattened. There are now imitation crackle textures rolled into glass.

Crown       Glass that is rotated as it is blown, thereby creating a disk shape with a knob, or crown, in the center. Same as Roundel.

Cut       Sculptural glass (three-dimensional, like a vase or goblet) that has designs cut into the glass with a copper wheel.

Curious       Glass that did not meet the manufacturer's specifications (in other words, "rejects"). Mostly this glass is very unusual, unpredictable, sometimes beautiful and sometimes ugly.

Cylinder       Most common type of blown glass. The glass bubble is blown into a cylinder, the ends cut off, the cylinder split along its length, and then unrolled into a flat sheet.

Dalle de Verre       "Slab of glass" (translation from the French) is a cast chunk of glass approximately 1" x 10" x 8" that is used to make "faceted" glass windows (see ?Faceted?).

Dichroic       Glass that has a thin metal film vaporized onto its surface. The glass transmits one color and reflects a different color. Each manufacturer offers about a dozen different color combinations.

Double-glazed       Two layers of glass with a seal around the edges. The edge strip usually contains a desiccant to prevent moisture accumulation between the glass surfaces.

Drapery       Glass with varying thickness and irregular ripples. It is made by pushing a hot sheet of glass across a tabletop into folds resembling fabric drapery.

Enameled       Glass design made by melting enamels on the surface of the glass.

Encapsulated       Glass which has been sealed inside a "sandwich" of two sheets of clear glass.

Etched       Glass with some of the surface removed by either a chemical or sandblast process. The result is that the glass is slightly thinner in the etched region and has a diffused reflective surface, thereby appearing whiter in color.

Faceted       Slab glass that has been chipped on the edges to cause thin flakes of glass to break off the flat surfaces. Pieces of this type of glass are set into an epoxy-concrete mixture to produce large architectural window-walls. The fractured edges ("facets") cause the light to bend and refract (break into a rainbow of colors).

Favrile       Type of glass produced by Louis Comfort Tiffany that is opalescent with a coppery metallic coating. Note: Starting in 1892, Tiffany called his glassware "Fabrile", supposedly, derived from the old English, meaning "hand-made". "Fabrile" evolved into "Favrile", which he trademarked on November 13, 1894. He used this word to apply to all of his glass, enamel, and pottery.)

Fired       Heated to a critical temperature in a kiln. The temperature depends on the glass and the desired effect. Painting becomes part of the glass about 1200 degrees F. Glass will slump or fuse (see definitions) at higher temperatures.

Flashed       The glass has a thin coating of a second color of glass processed onto the base glass. For example, most antique reds are made of clear glass with a very thin layer of intense red glass.

Flat       Glass art that has minimal thickness. The glass has NOT been worked into a three dimensional shape by being bent or fused or otherwise assembled or distorted.

FIBER BOARD:       One inch thick, high density fiber board. Gives the same insulating value as several layers of Fiber Blanket. Can be cut and machined like plasterboard. Upper limit of 2600 degrees.

FIBER PAPER:       One eighth inch thick. Excellent substitute for kiln wash. Perfect for slumping glass. Upper limit of 2600 degrees.

FIBER ROLL:       Is used to line a Glass Kiln.  It is a one inch thick, 8 lb density Fiber Blanket composed of alumina and silica fibers. Excellent for wrapping and insulating kilns, or Raku kiln construction. Upper limit of 2600 degrees.

FLASH VENT:       A quick-cooling step to be executed when a fuse glass or slump glass reaches VISUAL MATURITY, according to the judgment of the glass artist.

FLASH VENT       (for Fusing Glass): TURN OFF KILN POWER. Open kiln for 8 seconds, then close.

FLASH VENT       (for Slumping Glass): TURN OFF KILN POWER. Open kiln for 3 seconds, then close.

Float       Glass that is made by floating molten glass on a bed of mercury. This makes an extremely smooth and flat surface.

Fluted       Glass that has evenly spaced flutes running parallel to each other.

Fused       Two or more pieces of glass that have been melted together to form one piece.

Globs       Non-uniform round or oval smooth "puddles" of glass with one flat rough side formed by dripping glass onto a table.

Glue-chip       Glass that is covered with an animal glue and then dried in an oven. The glue shrinks and pulls chips out of the glass surface leaving a delicate, random, feathery, fern-like texture. This process can be repeated for a denser "double chip" appearance.

Grisaille       Black or brown fusible paint used for shading on glass. Grisaille glass is glass that has been painted and fired.

Hammered       Glass textured by indentations which resemble a surface that has been beaten with a ball-peen hammer.

Hot       Glass that has been worked by a hot process such as fusing, firing, blowing or lamp-working.

Impact-resistant       A type of engineered laminated glass that offers considerable resistance to impact from natural or man-made missiles impacting the glass. Bullet-proof and hurricane-proof glass.

Inlaid       A type of laminated glass where the art glass is laminated to a plate glass substrate by epoxy.

Insulating       Two pieces of glass that have been sealed together at the edges. The edge strip usually contains a desiccant to prevent moisture on the interior glass surfaces. The space between the glasses may be filled with argon gas.

Iridescent       Glass on which a very thin coating of metal has been applied. This thin coating reflects light from the upper and lower surfaces of the metal. These reflected light waves interfere with each other and produce a rainbow effect similar to that produced by a thin film of oil on water.

Jewel       Glass that is cast into molds with jewel-like facets and then polished to a smooth brilliance.

Laminated       A sandwich of two pieces of glass with a plastic-like material between them. In this type of safety glass, it is difficult to penetrate the glass even if both layers of glass break. Automobile windshields are made by this process.

Lamp-worked       Art glass that is made by heating with a torch and then "worked" in order to bend or fuse or shape the glass.

Leaded       iris stretched.jpg (61999 bytes)Type of art glass that is made by connecting pieces of glass with a lead channel and soldering the intersections of the lead channel. This has been the method of making church windows since the earliest times. Lead has the advantage of being strong enough to support the glass but flexible enough to withstand the thermal expansion stresses from the glass and the window encasement.

Liturgical       Glass designed for a prayer or worship space.

Low-E       Low E, (low emissivity), glass is high performance window glass made with an invisible thin metallic coating that blocks heat flow.

Medallions       A series of stained glass panels that have been arranged within a larger window in a narrative sequence.

Mosaic       Opalescent glass that has been sliced into small pieces (smalti) for assembly into designs that are cemented into building walls, floors or other surfaces. Mosaic pieces may also be composed of natural stone or ceramics.

Mottled       Glass that has variation in coloration in the form of small spots, some of which run together.

Obscure       Clear glass through which images cannot be can be seen because the light waves are bent by the texture on the glass surfaces. Obscure glass is used where light is desired but visibility is not, for example, in a bathroom.

Opak       Glass which has a thin coating of white on one side. This makes it behave somewhat like opalescent glass, but gives a more delicate effect which transmits more light.

Opalescent       rose cone lamp bight.jpg (15051 bytes) Glass containing some white pigment. The glass transmits some of the light striking it and reflects other light. Most of the glass used in the "Tiffany" style windows and lamps is opalescent glass.

Painted Glass with designs painted onto it and then fired so that the paint becomes part of the glass.

Plate       Thick, clear, smooth commercial glass. See "Float".

Plated       Multiple layers of glass used together to achieve a color not available as a single piece of glass. Tiffany often plated two or three pieces of glass to obtain the realistic shadings of images in his designs.

Protective-glazing       Glass (or other material) used to protect stained glass windows from external objects impacting them (e.g. tree limbs in a windstorm, rocks from vandals, etc.)

Reeded       Glass with uniform parallel ridges. Any dimension given specifies the spacing, for example, "1/2 inch Reeded glass."

Reinforced       Leaded glass that has been strengthened by the use of iron. Common methods are:

Residential       Art glass designed for residences.

Restoration       Clear glass that is manufactured to resemble glass made in the 18th and 19th centuries. This glass has some slight variation in thickness that causes some distortion.

Ripple       Glass with a ripple texture rolled into it while still molten. Various widths exist from fine (spaghetti ripple) to wide.

Roundel       Glass that is rotated as it is blown, thereby creating a disk shape with a thicker center and a cut-off from the punti (iron glass-working rod).

Safety       Glass with reduced hazard of injury when it breaks, and therefore specified by building codes for hazardous areas. The two main types are Tempered and Laminated. (see definitions).

Seedy       Glass that contains small bubbles or ?seeds?.

Slab       Glass poured into a mold to make small slabs of glass. See "Dalle de verre."

Smalti       Molten opalescent glass poured into pizza shape and then hand cut into small uneven squares (tesserae) used for assembling mosaics.

Stained       Colored glass assembled into designs. The color comes from the addition of metallic oxides during the process of melting the glass ingredients. The name comes from the silver nitrate that was used in the Middle Ages to "stain" clear glass yellow or orange when fired.

Tempered       Glass that has been heat treated to make it very hard and brittle. When the surface is broken anywhere, the entire piece of glass shatters into tiny pieces without sharp edges. The rear windows of automobiles are made of tempered glass.

Tessera       A small piece (normally square) of glass or marble used to make mosaics. (plural = tesserae)

Tiffany       Used to describe either:
A type of glass (see Opalescent and Favrile)
A style of glass art (produced in the studio of Louis Comfort Tiffany).

Transparent       Glass through which light passes freely. Glass through which objects on the other side of the glass can be seen.

Triple-glazed       Glass that has been sandwiched between two pieces of clear glass with the edges sealed. This is a common technique for insulating stained or beveled glass in doors.

Vaseline       Glass that is the color of petroleum jelly, emits slight radioactivity, and glows neon green under ultraviolet light.

Vision-obscuring       See Obscure. Opposite of transparent. Antique       Glass made by the "antique" method, namely by an artisan blowing a glass bubble that is formed into a cylinder, that is cooled, cut open, and then flattened in a reheat oven. This glass is characterized by variations in thickness that give the glass a gradient in color across each sheet. It usually also has some small air bubbles and/or variations in the refractive index that produce slight prismatic effects. ANTIQUE GLASS: Is produced  when a glass worker individually hand blows and rolls each sheet of glass. This process has been used since the middle ages, and results in brilliant transparent glass, with many striations and imperfections. The newer mechanized procedures results in glass known as semi-antique, new antique, or artique® glass.  Assistant - The glassworker that works directly for the Gaffer. In some situations, there may be several assistants depending on the size of the project.

APSLEY PELLATT GLASS: The Falcon Glass House in Blackfriars and a large showroom at St. Paul's Churchyard were part of the Pellatt and Green company.  Apsley Pellatt IV joined his father's in business, in London around 1811 at the age of 21.  Apsley ran the company when his father died in 1826 and changed the company name to Apsley Pellatt in the early 1830s.
Pellatt and prominent scientists Humphrey Davey and Michael Faraday, took a great interest in glass chemistry resulting in experiments on optical glass in the 1820s. He made decanters, paperweights, scent bottles, jugs, mugs, and various other items in clear high quality crystal glass with cameo incrustations to around 1850.
In 1819 Apsley Pellatt IV patented  "crystallo ceramie",  the process of encasing a medallion in glass, what is known today as the "Cameo Incrustation" and "Sulphides". He documented this process in 1821 he wrote a book,"Memoir on the Origin, Progress and Improvement of Glass Manufacture including .....Glass Incrustations", later revised the content Titled "Curiosities of Glass-Making".

APOTHECARY GLASS:  Small hand blown glass medicinal bottles have been used for storing and transporting medicines and the ingredients for medicines for nearly 2,000 years. The earliest ones were the Roman "unguentaria", sometimes called "teardrop bottles" made by the thousands.
The skilled glass worker would blow a tiny gather of glass into a bulb, pull the neck with his tools to elongate it, and then shear the vial from the blow pipe leaving a simple flared top.  Very few were made during the medieval times. During the "Renaissance" period small globular "footed" vials for medicines were made. Then the small cylindrical medicine bottle, popular from 15th century.

Architectural       Glass designed to become part of a building's structure. This term is used when the architect specifies the glass as part of the architectural design. ARCHITECTURAL GLASS:  Is designed to become part of a building's structure. An uses this term to specify the glass as part of the architectural design.

Art       A generic category that covers all artistic uses of glass as contrasted with functional use. Typical art glass types are stained glass, carved glass, fused glass, lamp-worked glass. ART DECO GLASS: Named from an exhibition in Paris in 1925 (the Exposition des Arts Decorative et industrial Moderns) where the finest French artists exhibited their pieces in this new style.
During the 1920's it was renounced for its opulence and exclusiveness". This style uses geometric patterns, bold colors, and animal motifs. Designers of the time were Rene Lalique, Maurice Marinot, Daum Freres, Sabino (all French) and from England, we must add Joblings.

ART NOUVEAU GLASS:  Art Nouveau, a style of decoration popular in the 1890's and 1900's lasting until War broke out in Europe in 1914. It uses free flowing motifs based on nature.  The name Art Nouveau is derived from a Paris gallery called 'Maison de L'Art Nouveau', which played a role in displaying and popularizing this style.
Think of this style as a feminine form, rounded and curving. Think of plant forms growing and burgeoning.
Many great artists made Art Nouveau Glass: including Galle, Louis C. Tiffany, the Daum brothers at Daum Nancy, Muller Freres, Loetz, and the Powells at Whitefriars.
As a reaction to the Victorian passion, Art Nouveau imitated earlier styles like Classical and Renaissance, Baroque and Rococco styles. These imitation works of art gave the Victorians a sense of security and confidence in their own affluence. Art Nouveau was something fresh, entirely new, and a break-away from the old traditions.

ARTS and CRAFTS GLASS:  The "Arts and Crafts" title came from the Arts and Crafts Exhibition Society, established in 1887 to show off designers' work in a range of materials and continued for some 50 years. As a a reaction against the extravagant, over-decorated Victorian taste and the worst features of factory production.
Well know designers were Walter Crane, William Morris, and Charles Robert Ashbee.  Taking a simple design made of inexpensive materials with a high standard was their goal.  They failed to change society in the way they intended because it was too expensive for "the masses".
Artique       An imitation of antique glass made by Spectrum Glass Company. The fine lines from a change of density in antique glass are molded into the surface of this glass giving a similar effect in a machine-rolled glass at lower cost than true antique blown glass.

Backing       A thin piece of glass used to hold together broken fragments of old glass by adhering to them (usually with silicone or epoxy).

Back-lighting       A method of using artificial light to illuminate stained glass not illuminated by sunlight.

Baroque       An artistic style of stained glass characterized by the use of curved lines and extravagant ornamentation.

Bent       Glass that has been bent by heating and , usually, forming it over a curved mold.

Beveled       Glass that has the edge cut off at an angle. This bends the light and produces a prismatic effect. The bevel is made by grinding off the edge of flat glass. Straight-edged bevels can be made by multiple machine grinding steps while curved edge bevels must be hand-made.

Blown       Glass made from blowing a glass bubble on the end of a hollow tube. An artisan may then shape it by spinning, rolling and pinching with iron tools to make a vase, bottle, glass or other object. Alternatively, the bubble may be placed into a hollow mold and further blown until it expands into all of the details of the mold.

Border       A band of glass that surrounds the main work in a window. It's purpose is to frame but also to allow removal of a non-essential area to adjust the fit of the stained glass to the window. It is often made of strips, geometric, or plant shapes.

Bottle       Sheet glass that is cut from the four sides of a glass bottle that was blown into a square mold. It has been replaced by the cylinder-blowing method described under "Antique."

Carved       Glass with the appearance of a three-dimensional sculpture imprisoned within the glass. This is achieved by etching the glass to varying depths.

Cast       Glass made by pouring molten glass into a mold.

Cathedral       Transparent glass of uniform thickness made by squeezing molten glass between rollers. The color is uniform across the piece of glass (no color gradient). Usually one roller is smooth and the other textured, which gives texture to the glass. (See "Hammered" below for one of the more popular textures).

Copper-foiled       Copper-foil is a method for making 2 or 3-dimensional objects from small pieces of colored glass. Very thin strips of copper foil are wrapped around the edges of each piece of glass. The pieces are positioned into the desired shape or design and then soldered together. The copper foil is completely hidden underneath the solder, which is usually blackened by application of a patina-forming chemical. Stained glass lamps of all shapes are made by this method.

Crackle       Glass made by dipping a molten cylinder into water. The exterior of the cylinder cracks but the molten interior holds it together. The cylinder is sliced down the side and flattened. There are now imitation crackle textures rolled into glass.

Crown       Glass that is rotated as it is blown, thereby creating a disk shape with a knob, or crown, in the center. Same as Roundel.

Cut       Sculptural glass (three-dimensional, like a vase or goblet) that has designs cut into the glass with a copper wheel.

Curious       Glass that did not meet the manufacturer's specifications (in other words, "rejects"). Mostly this glass is very unusual, unpredictable, sometimes beautiful and sometimes ugly.

Cylinder       Most common type of blown glass. The glass bubble is blown into a cylinder, the ends cut off, the cylinder split along its length, and then unrolled into a flat sheet.

Dalle de Verre       "Slab of glass" (translation from the French) is a cast chunk of glass approximately 1" x 10" x 8" that is used to make "faceted" glass windows (see ?Faceted?).

Dichroic       Glass that has a thin metal film vaporized onto its surface. The glass transmits one color and reflects a different color. Each manufacturer offers about a dozen different color combinations.

Double-glazed       Two layers of glass with a seal around the edges. The edge strip usually contains a desiccant to prevent moisture accumulation between the glass surfaces.

Drapery       Glass with varying thickness and irregular ripples. It is made by pushing a hot sheet of glass across a tabletop into folds resembling fabric drapery.

Enameled       Glass design made by melting enamels on the surface of the glass.

Encapsulated       Glass which has been sealed inside a "sandwich" of two sheets of clear glass.

Etched       Glass with some of the surface removed by either a chemical or sandblast process. The result is that the glass is slightly thinner in the etched region and has a diffused reflective surface, thereby appearing whiter in color.

Faceted       Slab glass that has been chipped on the edges to cause thin flakes of glass to break off the flat surfaces. Pieces of this type of glass are set into an epoxy-concrete mixture to produce large architectural window-walls. The fractured edges ("facets") cause the light to bend and refract (break into a rainbow of colors).

Favrile       Type of glass produced by Louis Comfort Tiffany that is opalescent with a coppery metallic coating. Note: Starting in 1892, Tiffany called his glassware "Fabrile", supposedly, derived from the old English, meaning "hand-made". "Fabrile" evolved into "Favrile", which he trademarked on November 13, 1894. He used this word to apply to all of his glass, enamel, and pottery.)

Fired       Heated to a critical temperature in a kiln. The temperature depends on the glass and the desired effect. Painting becomes part of the glass about 1200 degrees F. Glass will slump or fuse (see definitions) at higher temperatures.

Flashed       The glass has a thin coating of a second color of glass processed onto the base glass. For example, most antique reds are made of clear glass with a very thin layer of intense red glass.

Flat       Glass art that has minimal thickness. The glass has NOT been worked into a three dimensional shape by being bent or fused or otherwise assembled or distorted.

Float       Glass that is made by floating molten glass on a bed of mercury. This makes an extremely smooth and flat surface.

Fluted       Glass that has evenly spaced flutes running parallel to each other.

Fused       Two or more pieces of glass that have been melted together to form one piece.

Globs       Non-uniform round or oval smooth "puddles" of glass with one flat rough side formed by dripping glass onto a table.

Glue-chip       Glass that is covered with an animal glue and then dried in an oven. The glue shrinks and pulls chips out of the glass surface leaving a delicate, random, feathery, fern-like texture. This process can be repeated for a denser "double chip" appearance.

Grisaille       Black or brown fusible paint used for shading on glass. Grisaille glass is glass that has been painted and fired.

Hammered       Glass textured by indentations which resemble a surface that has been beaten with a ball-peen hammer.

Hot       Glass that has been worked by a hot process such as fusing, firing, blowing or lamp-working.

Impact-resistant       A type of engineered laminated glass that offers considerable resistance to impact from natural or man-made missiles impacting the glass. Bullet-proof and hurricane-proof glass.

Inlaid       A type of laminated glass where the art glass is laminated to a plate glass substrate by epoxy.

Insulating       Two pieces of glass that have been sealed together at the edges. The edge strip usually contains a desiccant to prevent moisture on the interior glass surfaces. The space between the glasses may be filled with argon gas.

Iridescent       Glass on which a very thin coating of metal has been applied. This thin coating reflects light from the upper and lower surfaces of the metal. These reflected light waves interfere with each other and produce a rainbow effect similar to that produced by a thin film of oil on water.

Jewel       Glass that is cast into molds with jewel-like facets and then polished to a smooth brilliance.

Laminated       A sandwich of two pieces of glass with a plastic-like material between them. In this type of safety glass, it is difficult to penetrate the glass even if both layers of glass break. Automobile windshields are made by this process.

Lamp-worked       Art glass that is made by heating with a torch and then "worked" in order to bend or fuse or shape the glass.

Leaded       iris stretched.jpg (61999 bytes)Type of art glass that is made by connecting pieces of glass with a lead channel and soldering the intersections of the lead channel. This has been the method of making church windows since the earliest times. Lead has the advantage of being strong enough to support the glass but flexible enough to withstand the thermal expansion stresses from the glass and the window encasement.

Liturgical       Glass designed for a prayer or worship space.

Low-E       Low E, (low emissivity), glass is high performance window glass made with an invisible thin metallic coating that blocks heat flow.

Medallions       A series of stained glass panels that have been arranged within a larger window in a narrative sequence.

Mosaic       Opalescent glass that has been sliced into small pieces (smalti) for assembly into designs that are cemented into building walls, floors or other surfaces. Mosaic pieces may also be composed of natural stone or ceramics.

Mottled       Glass that has variation in coloration in the form of small spots, some of which run together.

Obscure       Clear glass through which images cannot be can be seen because the light waves are bent by the texture on the glass surfaces. Obscure glass is used where light is desired but visibility is not, for example, in a bathroom.

Opak       Glass which has a thin coating of white on one side. This makes it behave somewhat like opalescent glass, but gives a more delicate effect which transmits more light.

Opalescent       rose cone lamp bight.jpg (15051 bytes) Glass containing some white pigment. The glass transmits some of the light striking it and reflects other light. Most of the glass used in the "Tiffany" style windows and lamps is opalescent glass.

Painted Glass with designs painted onto it and then fired so that the paint becomes part of the glass.

Plate       Thick, clear, smooth commercial glass. See "Float".

Plated       Multiple layers of glass used together to achieve a color not available as a single piece of glass. Tiffany often plated two or three pieces of glass to obtain the realistic shadings of images in his designs.

Protective-glazing       Glass (or other material) used to protect stained glass windows from external objects impacting them (e.g. tree limbs in a windstorm, rocks from vandals, etc.)

Reeded       Glass with uniform parallel ridges. Any dimension given specifies the spacing, for example, "1/2 inch Reeded glass."

Reinforced       Leaded glass that has been strengthened by the use of iron. Common methods are:

Residential       Art glass designed for residences.

Restoration       Clear glass that is manufactured to resemble glass made in the 18th and 19th centuries. This glass has some slight variation in thickness that causes some distortion.

Ripple       Glass with a ripple texture rolled into it while still molten. Various widths exist from fine (spaghetti ripple) to wide.

Roundel       Glass that is rotated as it is blown, thereby creating a disk shape with a thicker center and a cut-off from the punti (iron glass-working rod).

Safety       Glass with reduced hazard of injury when it breaks, and therefore specified by building codes for hazardous areas. The two main types are Tempered and Laminated. (see definitions).

Seedy       Glass that contains small bubbles or ?seeds?.

Slab       Glass poured into a mold to make small slabs of glass. See "Dalle de verre."

Smalti       Molten opalescent glass poured into pizza shape and then hand cut into small uneven squares (tesserae) used for assembling mosaics.

Stained       Colored glass assembled into designs. The color comes from the addition of metallic oxides during the process of melting the glass ingredients. The name comes from the silver nitrate that was used in the Middle Ages to "stain" clear glass yellow or orange when fired.

Tempered       Glass that has been heat treated to make it very hard and brittle. When the surface is broken anywhere, the entire piece of glass shatters into tiny pieces without sharp edges. The rear windows of automobiles are made of tempered glass.

Tessera       A small piece (normally square) of glass or marble used to make mosaics. (plural = tesserae)

Tiffany       Used to describe either:
A type of glass (see Opalescent and Favrile)
A style of glass art (produced in the studio of Louis Comfort Tiffany).

Transparent       Glass through which light passes freely. Glass through which objects on the other side of the glass can be seen.

Triple-glazed       Glass that has been sandwiched between two pieces of clear glass with the edges sealed. This is a common technique for insulating stained or beveled glass in doors.

Vaseline       Glass that is the color of petroleum jelly, emits slight radioactivity, and glows neon green under ultraviolet light.

Vision-obscuring       See Obscure. Opposite of transparent