Stained Glass Dictionary
Abrasive Etching – (sand blasting) the process used to remove material from the surface of the glass using various abrasive materials such as garnet, silicon carbide or sand propelled by compressed air. Most often performed on clear or lightly tinted glass to create a wide range of designs ranging from simple signage to deeply carved portraits and scenes.
Acid Etching – The process used to remove the colored veneer from flashed glass to expose the underlying color allowing two distinct colors of glass on a single piece, or to shade the color to create a high-light or shadow.
Aisle – The areas of the Nave that separate the pews from the walls or the pews into distinct sections.
Alabaster Opalescent – White glass without the “opal” glow in transmitted light. Often referred to as sign glass.
Ambulatory – A walkway behind the Sanctuary connecting the Sacristies out of view of the congregants.
Annealing – A method of controlled cooling of glass through the temperature range 950° – 800° F. to remove internal stress. This allows the glass to expand and contract freely without fracturing and to be cut into shapes that are stable.
Antique Glass – Hand blown sheet glass exhibiting unique qualities created by blowing molten glass into a cylinder that is annealed, cut longitudinally, reheated and flattened to form a flat sheet. Glass created in this fashion usually exhibits a full range of qualities, including but not limited to, straw lines, seeds, bird’s eyes, streaks, and shading due to thickness changes within the sheet. Most flashed glass falls into the category of antique glass.
Apse – Traditionally, the east facing semi-circular end of the church where the Altar is located with a vaulted ceiling above.
Arbitrary Lead Lines – Lines that do not delineate the main theme but are used to breakup background areas to modulate color or to form cut-able pieces.
Art Nouveau – “New Art” one of the prominent styles of the late 1800’s to early 1900’s where designs are based on stylized symmetrical flowing floral patterns.
Art Speak – Meaningless words used to sell a project using “feeling, mood or attitude” of a color, or otherwise meaningless design element.
Arts and Crafts Movement – English style that developed as a revolt against mass-produced decoration from the 1850’s to the 1890’s popularized by artist-poet William Morris, painter and designer Sir Edward Burne-Jones and others.
Aureole – Symbolizes divinity and supreme power and reserved for the Father, Son and Holy Spirit in Christian Art. See Halo and Nimbus.
Awning Window – An operating or ventilating portion of a window where the bottom portion pushes out and the top remains in plane.
Azure Blue – Sky blue.
Back Light – The natural or artificial light projected from the opposite side from which the window is observed.
Back Painting – Vitreous paints and glazes applied to the backside of the glass to exaggerate depth of color, create a softer less defined image, or to apply a stain that will alter the transmitted color.
Backer Rod – Flexible foam rod that is compressed around a window to take up space prior to caulking the stained glass or protective glass.
Baldachin – Is a canopy of state over an altar or throne. It had its beginnings as a cloth canopy, but in other cases it is a sturdy, permanent architectural feature, particularly over high altars in cathedrals.
Ball Mill – Rotating closed chamber with steel balls used to finely grind glass paint.
Balsam of Copaiba – A viscous slow drying oil from Brazil and Venezuela that is sometimes used by glass painters to add body to other oil based media.
Banderole – Design element in the shape of a banner or ribbon on to which and inscription is painted.
Banding – Soldering tie-wires or lead strips to the surface of the window for the purpose of wrapping around steel reinforcing bars.
Banding Medium – One of the most versatile oil based painting media. It dries quickly, and is abrasion resistant prior to firing in the kiln. It is clean burning as is especially useful for applications of transparent stains or for airbrushing.
Baroque –is a period of artistic style that used exaggerated motion and clear, easily interpreted detail to produce drama, tension, exuberance, and grandeur in sculpture, painting, architecture, literature, dance and music. The style began around 1600 in Rome, Italy and spread to most of Europe during the 16th and 17th centuries.
Basilica – Church in the style of ancient Rome with semi-circular apse and raised nave.
Batch – Raw materials used to melt into glass made of cullet, silica, fluxes, de-colorants and metallic colorants.
Bay Window – Typically a three-sided window that projects to the exterior of a wall.
Bead – A small strip of wood or metal used to mechanically hold a stained glass window or storm window into the supporting frame.
Bema – The enclosed area surrounding the altar in Eastern Orthodox Churches.
Bevels – Glass, typically ¼” or thicker, that has a ½” – 1-½” wide polished edge oriented at a 30° – 60° angle to the surface of the glass.
Bevel Cluster – 2 or more bevels that fit together and that are used together.
Billy Hammer – A small carbide edged hammer used to facet Dalle de Verre with conchoidal fractures.
Black Mirror – (Claude Glass) A black, convex glass that reflects a view in miniature, eliminating color and detail. Used by 17th century painters to review composition.
Blender Brush – Glass painting brush, typically 5” wide and used clean and dry, to uniformly disperse wet paint already applied to the surface of the glass.
Blister – Imperfection in the glass paint after it has been fired. Usually caused by improper cleaning of the glass before painting or applying the paint too thickly.
Blocks – Concave glass blowing tool resembling a paddle used to shape the gather or bubble while molten. Usually kept wet to prolong their life.
Bloom – Unwanted film left on the glass surface after firing. Caused by fumes or smoke burning off during the firing process. Also refers to corrosion on the lead or glass from flux, patina, caulk, or cement residue.
Blow Pipe – (Blow Iron) Hollow metal tube 4’ – 5’ long with an enlarged end used to gather the molten glass for blowing.
Boil – Escaping gas bubbles that rise up through fully fused and hotter kiln formed work.
Brass – An alloy of copper over 50% and zinc less than 35%
Brass Jacketed Lead- Lead with a thin cover of brass folded over the “crown” or “hat” to add strength.
Bridge – Used for resting the hand above the surface of the glass while painting on a light table or easel.
Brilliant Cutting – Stone engraved and polished indentation usually found in glass thicker than ¼”.
Bronze – An alloy of 90% Copper, 7% tin and 3% zinc.
Bugs – Tempering marks found in the lower right inside corner. Not all tempered glass is labeled with a ‘bug’.
Bulge – (Bow) Area of a leaded panel deflected out from the plane of the glass. Usually an early indicator of lead deterioration but can also occur in panels that where not installed with enough edge clearance, failing frames and armatures, insufficient reinforcing, or structural weaknesses in the design.
Burnish – To rub flat and smooth.
Buttering – The first application of putty into a sash to accept the glass or panel.
Butt Joints – Used for ¼” and smaller H round lead. Cutting lead back from the edge of the glass slightly more than the minimum required for a tight fit to allow the glass to move slightly in the lead.
Byzantine – Religious art from what is now Turkey, created between 330 -1550. Exemplified by frescos, mosaic and stone carvings. Highly stylized with elaborate organic and geometric designs.”C”
Cabochon – Convex or domed shaped jewel, polished but not faceted.
Carborundum Stone – A sharpening stone that can also used to smooth the rough or sharp edges that sometimes occur when cutting glass.
Came – (calm) The lead channels used to assemble the cut pieces of glass in a stained or leaded glass window. Available in a myriad of shapes, sizes and weights and can be made of lead, zinc or copper.
Camel Hair Brush – Soft glass inexpensive painters brush made from squirrel, sable, goat or pony hair. It is not made from camel hair.
Cane – Glass rod made from one or more fused glasses pulled to reduce the diameter while retaining the same cross sectional pattern.
Canopy – Window design element imitating architectural details surrounding figures or scenes. Usually originates at the bottom of the window in the form of columns and becomes very elaborate arched form in the upper portion of the window.
Cartoon – A full size working drawing of the window including both the lead lines and the painted details. Used as a guide for painting and is the basis for all subsequent steps. Usually charcoal on white paper but some times colored with pastels or watercolors.
Casement Window – An operable window with hinges mounted on either the left of right sides.
Cased Glass – Layered glass, often fused or blown, that produces two or more distinct layers of glass. Flashed glass is the most common example.
Casping – Protruding points found in Gothic tracery.
Cast Glass – Glass made by pouring molten glass into a hot steel or graphite mold and compressing flat. Faceted glass jewels are an example of cast glass.
Cathedral Glass – Machine rolled glass ranging from transparent to opalescent. Glass can be smooth or textured, exhibits uniform thickness, lacks the fire polish surface of antique glass, and can include seeds, flow lines and other unique characteristics. Sheets can be larger and are more uniform in appearance
Catspaw Glass – A unique surface texture usually found in opalescent and streaky cathedral glass that appears spotted.
Caulk – Mastic used to seal the edges of finished glass panels to the frame or the frame to the building during installation.
Cement – Mastic comprised of whiting, boiled linseed oil, and lamp black that is brushed or pushed between the lead and the glass to waterproof the stained glass window.
Chancel – The eastern part of the church containing the choir and the altar.
Channel – A “U” shaped grooved section of lead that accepts the glass.
Chiaroscuro – The light end or highlight of a transition from dark to light when shading to create a more three dimensional composition.
Check – Surface crack typically caused by improper annealing where the surface was cooled to quickly.
Chill Marks – Surface imperfections found on blown glass or machine rolled glass caused by using improperly preheated tools, rollers, or casting tables.
Choir – The eastern part of the church where the choir sits often separated from the nave by a rail of screen.
Clamshell – Conchoidal fracture or chip on the flat surface of the glass caused by impact. Used on the periphery of Dalle de Verre glass to add brilliance and sparkle.
Clerestory – The upper portion of a wall containing windows to allow natural light into the nave, transepts and choir of a church.
Cloisters – A covered walkway beside the walls of an inner courtyard.
Clove Oil – A drying inhibitor when mixed with other oils in glass painting. When used alone it allows pen and quillwork. Can be thinned with lavender oil.
Coefficient of Expansion – The unique amount of change in size for a given compound relative to increases and decreases in temperature.
Cold Glass – Term used to describe glass that has been ground, engraved, etched etc. without the use of heat.
Cold Joint – A low temperature solder joint where the solder mounds on top of the lead instead of blending into the lead.
Color Intensity – The purity or brilliance of a color sometimes referred to as chroma.
Colonial Lead – A came with a heart raised higher than the leaf.
Conchoidal Fractures – Smooth irregular concave cracks resembling clamshells. Typical of the facets in Dalle de Verre windows. May appear at the point of impact.
Confetti Glass – Cathedral or opalescent glass with chips of colored blown glass added to the surface and fused during the rolling process.
Conservation Tape – A tape used to stabilize fractured glass or unstable windows during removal. Adhesive is less aggressive than most tapes and dissolves easily with acetone.
Contour – The lead used to outline a figure, medallion or other image that is wider than the others being used.
Contrasting Colors – Complementary colors placed side by side to intensify their effect.
Copper Foil – Thin adhesive backed copper of various widths that are used to wrap a piece of glass intended to but up against another piece of glass that has been wrapped with copper foil. Pieces are butted up against one another and soldered continuously along the seam. Using copper foil technique produces an organic line of varying width compared to the more architectural looking static width of lead came lines.
Copper Stain – Mythical red glass stain similar to silver stain but made of unknown ingredients.
Copper Sulfate – Used in solution to produce a copper colored patina on solder.
Coptic Art – Egyptian Christian work produced from the 4th to the 7th century.
Cord – A ream or optical ripple in the glass caused by chemical inhomogeneity, visible due to a difference in refraction between the composition of the cord and the base glass. See Reamy.
Cork Wheel – First polishing surface used with pumice to polish beveled glass.
Craquel Glass Texture – A texture on antique glass reminiscent of alligator skin created by quick quenching the bubble in water during the blowing of the initial bottle.
Craftsman Style – (Prairie Style) Early 1900’s Midwest style typified by simple geometric shapes. Frank Lloyd Wright’s work best exemplifies the style.
Crazing – Cracking within a fused piece of glass that randomly occur due to incompatible coefficient of expansion of the glasses used.
Cristallo – (crystal) a type of clear colorless late 12th century Venetian glass made from soda ash and lightly decorated with enamels.
Crown Glass – (roundels, spun glass) Spun plate like round sheets of glass ranging from 2” to 24” in diameter created in a wide range of colors.
Crow Quill – Fine steel drawing pen, used from removing fine details from dry, unfired glass paint.
Crucible – Refractory pot used to melt the batch in to glass.
Cullet – Broken glass used in the batch to lower the melting time/ temperature when making new glass.
Curtain Glass – Heavy ripples or folds in the glass thickness, less regular and thicker than ripple glass but thinner than drapery glass.
Cusp – Small protruding points of stone in Gothic tracery.
Cutting Oil – Lubricating fluid used on the cutting wheel and axle. Kerosene is commonly used.
Cutline Drawing – Copy of the cartoon without the paint details used as patterns to cut the glass and to lay the glass out after it is cut.
Cyan – Dark Blue
Dalle de Verre – glass cast into 1” thick forms measuring approximately 8” x 12”. Glass is cut using diamond saws, glasscutters, anvils, and hammers. The edges of the cut pieces are usually faceted with conchoidal fractures and then cast in an epoxy resin into completed panels. Process was developed in France c.1929 by Jean Gaudin, A. Labouret and others.
Damar Gum – Glass painting medium that give a very opaque black trace line in a single firing without cracking or boiling. Drying time can be extended with clove oil. Made from the resins of evergreen trees found in Southeast Asia, Australia, and New Zealand.
Danziger – German name for water glass or reamy like sheet glass.
Daylight Measurement – What is visible through the window frame.
Decolorizing Agent – Chemicals added to glass batches that mask impurities resulting in clearer glass.
Decorative Solder – By manipulating the tip of the soldering iron, decorative textures can be added to the surface of the copper foil or lead came. This is done with a cooler iron temperature that what is used to solder the window together.
Decorated Style – The second phase of English Gothic architecture c. 1300 to 1400.
Deka® – Non fired transparent glass paint made in Germany. Often referred to as cold paint, or cold color.
Delcalcomania – (tonking) The act of creating a random pattern formed by removing wet paint by blotting.
Devitrification – To take away the glassy surface or develop a crystalline formation. This can occur in modern glass by over heating in the kiln, or in medieval glass due to chemical breakdown.
Diaper – French word describing the border around the window decorated with a pattern of repeated small figures or shapes. Also used to describe elaborate stick lighting in the background of medallions.
Dichroic Glass – High tech glass with a molecularly thin, vacuum chamber deposited, metallic coating. Glass reflects one spectrum of color while transmitting another depending on the viewing angle.
Divider Bar – A thin mullion or muntin made of wood, metal or stone that divides the window into separate panels.
Dividing Iron – Medieval glass cutting tool. The hot tip of the iron is drawn across the surface of the glass allowing it to break along the line.
Dome – Non-flat skylight window often shaped like a hemisphere.
Door Light – Window within a door.
Double Glazed – Two layers of glazing installed in a single opening, one being the stained glass and the other being a storm window or protective glazing, set apart by a fixed separator.
Double Hung Window – Window with a lower inner sash that slides up past the upper outer sash and the outer upper sash that can slide down past the lower inner sash.
Drapery Glass – Thick opalescent glass that has been manipulated and folded to look like wrinkled cloth while molten.
D.S. – (Double Strength) window glass measuring ⅛” thick.
Dutchman – lead leaf placed over a crack and tucked under the lead at termination to hide a crack and mimic a lead line.
Early English Style – The first of three Gothic styles found in England dating from 1190 -1280 with a pointed arch topped lancet window without mullions, often set in sets of 3, 5, and 7.
Easel – Painting Easel is a sheet of ¼” thick plate glass set up in front of a window or light source to allow color composing and painting with natural or artificial light. Glass that is to be painted is affixed to the easel with easel wax.
Easel Wax – A blend of bee’s wax, rosin & cornstarch used to hold cut pieces of glass to the easel for painting. Wax is heated to liquid than applied with an eyedropper.
Enamels – Fluxed and fritted powdered glasses mixed with oxides for color, painted on the glass surface, and fired in a kiln to ±1100° F. to change the color or create an image.
English Stippler – Glass painting brush made from boar’s hair used to alter the previously matted surface prior to firing.
Epoxy Resin – Material used to hold Dalle de Verre windows together.
Etching – The act of removing or altering the surface of the glass by exposing it to acid or compressed air propelled abrasives.
Eye Window – Round window without tracery. See oculus.
Faceted Glass – A colloquialism for Dalle de Verre.
Favrile Glass – A line of glass with an iridescent metallic sheen first created by Louis Comfort Tiffany in the 1880’s to imitate very old buried glass.
Felt Wheel – Used with cerium oxide for final polishing of glass bevels.
Fenestration – Architectural term that applies to the grouping and design in building windows.
Fibroid – A glass texture with many fine ridges mixed with a loose ripple pattern.
Fid – (lathekin) Wood, plastic or Teflon device used to manipulate lead around glass or to widen the heart of the lead to accept thicker glass.
Field – Background section of a window separating the central theme from the border.
Fillet – Thin strips of glass often found in window borders or between design elements.
Fined Glass – Glass without seeds, birds-eyes or other internal forms. Typically made by heating the glass longer than normal.
Fipple – Texture with many fine ridges mixed with a ripple surface.
Fire Brick – Hard, dense, refractory building block used for hot glass melting furnaces capable of withstanding 2400° F. temperatures and prolonged hot glass contact.
Fire Cracks – Localized irregular crazing or cracks caused by excessive heat. Often occur in fire-damaged glass.
Fire Flies – Glass breaking or cracking after firing due to poor annealing.
Fire Polish – Smoothing or returning glass surface to a shinny state with heat or open flame.
Fire Proof Archival Paper – A thin high temperature refractory sheet developed in Japan, used both to protect important documents from fire and between the glass and the shelf in kilns.
Firing – The heating of glass in excess of 1000° F. to permanently set applied paints and decorations.
Flaking – Flashed or streaky colored glass that spontaneously separates due to chemical incompatibility.
Flanging – To solder an extra piece of lead onto a lead came to cover the edge of thick glass.
Flash Kiln – Large gas kiln with shallow arched top and burners on two sides used in traditional American studios to quickly fire painted glass.
Flashed Glass – Blown glass with a thin veneer of a second color on one side of the sheet.
Flemish Glass – Cathedral glass with a broad wavy texture on both sides.
Flint Glass – Glass with a high index of refraction containing lead.
Flints – Smaller pieces set into rectangular or diamond background fields to break up the geometric design imitating old windows.
Floating Rebar – Window support bar soldered to the surface across a section likely to deform that is not anchored into the sash, frame, or another bar.
Fluid Writers – Painting tool used for depositing uniform thin line of glass paint much like a pen.
Flux – (1) Used to clean and protect from oxidation surfaces being heated for soldering. (2) Clear glaze or enamel used to lighten or thin colored enamels or to help attach fused glass.
Float Glass – Window or plate glass produced by floating hot glass over molten tin.
FMA – (FNA) French machine made glass that resembles antique glass without bubbles, streaks, or shading caused by varying the thickness.
Foil – (1) Small arc opening in Gothic tracery. The number of foils is indicated by a prefix. Trefoil – 3, Quatrefoil – 4, Cinquefoil – 5. (2) Adhesive backed thin copper strips used to hold glass together. (3) Thin metallic sheeting used to between fused glasses to produce an opaque metallic effect.
Frit – (1) A fused vitreous material that has been broken down into small particles used as a base for enamels and glazes. (2) Broken, ground glass used to lower the melting temperature of glass. (3) Crushed glass used for fusing or Pate de Verre glass casting.
Front Surface Mirror – Sheet glass with a mirrored surface on the topside removing the refraction and distortion created by traditional back surface mirror. Used with lasers for holography or in telescopes to remove refraction caused by light passing through the glass.
Frosted – Surface treatment that removes the shinny or glass like surface but does not deeply penetrate the glass. Usually performed with acid or abrasives.
Fry – Over fired or over applied glass paint resulting in an undesirable pock marked surface.
Fulgurite – Naturally formed, irregular tube shaped, glass made when lightening strikes sand.
Full Fuse – The combining of two similarly compatible glasses in the kiln at a higher temperature than fusing such that they lose their unique original shape and form on glass.
Fuming – (1) Creating a thin metallic surface on hot glass by exposing glass to the fumes of metallic chlorides in a reduction environment. See iridescence. (2) Exposing the surface of a glass to the acid vapors to uniformly remove the fire polish or etch the surface.
Fusing – The combining of two or more compatible glasses in the kiln to form one glass while retaining some of the unique shape qualities of the original glasses.
Gaffer – Master glass blower
Garnet Abrasive – 80 – 150 grit garnet is used a an effective compressed air propelled abrasive, lasting longer than sand as it cracks into sharp pieces as opposed to turning into fine dust and is less expensive though not as long lasting as silicon carbide.
Gauge Cutting – Technique used to production cut uniform sizes in quantity.
Gauntlets – Reinforced fabric forearm protectors, used to prevent cuts when handling sheet glass.
German Glazing Nails – Round, tapered, sharp nails used with a bit of lead to hold pieces of glass together when assembling windows.
Gesso – Canvas priming paint made of gypsum. Useful for painting wood or Styrofoam molds prior to designing.
Glare – Surface light that reduces the amount of light viewed through he stained glass, resulting from unglazed windows in the same room or clear or very light glass juxtaposed with dark colored glass.
Glass – A hard, vitreous, non-crystalline, silica based compound typically comprised of fluxes, de-colorants, and colorants created with heat above 1600° F.
Glass Bending Colors – These are a line of glass paints called “Architectural Appliance and Bent Glass Colors”. They are translucent with the blues being almost transparent. The colors, red, orange, yellow, green, blue, brown as well as black and white and can be blended as required to create other colors.
Glass Blowing – The technique of working molten glass on the end of a pipe invented about the 1st century BC by the Phoenicians.
Glass Brush – Spun glass fibers bound into a round short bristled brush, used to burnish and clean metal and enamels.
Glass Cups – Handled suction cups used to help move heavy plate glass.
Glass Gloves – Reinforced rubber gloves used to add grip and protect hands when moving heavy or sharp sheet glass.
Glass Muller – A flat bottomed pedestal like tool made of glass, used for grinding coarser paints.
Glass Paint – (Glass Stainers Colors) Fluxed and fritted powdered glass that fuse to the base glass and effect light transmittance, but not necessarily the color of the glass.
Glass Stainers Enamels – These are lower temperature firing colors used to paint on glass. A full range of colors that range from transparent to obaque.
Glass Stainers Kiln – Gas fired oven used to fire glass paints to the surface of the base glass.
Glazier – A craftsperson skilled in the techniques of working with windows and glass.
Glaziers Pie – The bulging up from the table of an unsoldered leaded window due to too much lateral force being applied from the surrounding area. Windows should never be forced together in such a way that creates a glaziers pie.
Glazing Points – Mechanical fasteners made from galvanized metal used to hold glass into wood frames.
Glazing putty – White or gray compound used to hold windows wood or metal sash.
H Lead or Zinc – Basic shape of the metal used between the individual pieces of glass comprising a stained glass window. Shaped like the capital letter “H” with two channels to receive the glass separated by the “heart”. The flanges that hold the glass in plane are referred to as the “leaf”. Available in virtually any size and can have flat, semi-round, round, embossed, or colonial leaf.
Hack-Out-Border – Narrow band of pastel common glass intended to be sacrificed during the removal of the window for repairs or restoration. Light color is intended to illuminate the cut tracery.
Hack-Out-Knife – Steel cutting tool used to remove old hard putty.
Halation – A spreading or refraction of light, through light colored glass, beyond the lead line or border of a window much like a halo around highlights.
Halo – Round, square or triangular shaped symbol located behind the head representing a sacred or divine being.
Halo Lusters – Thin iridescent coating with rings of concentric circles painted onto glass or ceramics and fired into the glass.
Hammered Glass Texture – Rolled cathedral glass with the surface that looks like it was hit repeatedly with a ball-peened hammer.
Hard Brick – Dense alumna firebrick used in glass blowing furnaces for its resistance to heat and corrosion.
Herringbone Ripple – A hand rolled glass that is like a ripple but has an alternating herringbone pattern with high relief.
High Heart Lead – “H” shaped metal with a tall heart to receive thick or multiple layers of glass within a single channel.
High Point – (colonial) Metal came profile with a pyramid shaped leaf that adds strength without increasing the daylight size of the lead. Common to prairie style windows.
Highlighting – Removing dried matte painting prior to firing to allow more light through.
Hollow Heart Lead – Specialized lead came that allows a thin steel bar to be slide into the hollow of the heart. Adds strength to a window and is usually found on continuous vertical leads, but can be used on horizontal ones in lieu of surface reinforcing bars.
Hopper Window – An operable window that is hinged to allow the top of the sash to pull in from the top.
Horse Shoe Nails – (Farrier’s Nails) Tapered flat sided nail used to hold lead or glass in place during fabrication.
Hot Glass – Term used to describe furnace or flame worked glass as in glass blowing.
Hot Joint – Too much heat from the soldering iron causing the solder to flow under the leaf and into the channel.
House Bevel – Five sided beveled glass shape with three 90° and two 120° corners.
Hydrofluoric Acid – Acid used to etch glass or remove the flash from flashed glass.
Hypostyle – Room with a roof supported by pillars.
Inclusion – An object encased in the glass during the process of making the glass. Most commonly un-melted batch material floating in the glass.
In Situ – On site or in original position.
Insulated Glass – Two layers of glass separated by spacer sealed into a single unit. Inert gas or slight vacuum often introduced between the layers.
Iridescent Glass – Rainbow reflective surface treatment that looks like oil on water.
Iridescent Lusters – A thin iridescent coating painted on the surface of the glass and fired.
Jacks – (Tongs, Pucellas) Steel hot glass forming tool that look like shears but are used to indent or stretch the glass on the pipe as hot glass is being formed. Lubricated with wax.
Jade – Medium green glass.
Jalousie – Louvered window made of wood, metal or glass in the form of horizontal slats used to regulate the passage of air or light.
Jamb – Side framing in a door or window opening.
Jamb Pocket – Sash opening used to access window weights on double-hung windows.
Japan Drier – One of the slower acting drying additives used to speed up the setting of window cement.
Jean Cousin – Red stain used to paint flesh color in the 15th and 16th centuries. Exact formulation is unknown and has not yet been duplicated.
Jewel – Three dimensional, pressed, sometimes faceted and polished, usually transparent, semi-transparent or containing opal color.
Jube – Loft or gallery over the rood screen (between the Nave and Chancel) in a church.
Kerosene – A thin fuel oil used as a glasscutter lubricant. Can also be mixed with glass paints to apply additional layers of paint over top of unfired water based matte paints.
Kiln – An insulated electric or gas oven used to heat glass or ceramics to fire glass paints, stains, and ceramic glazes to temperatures between 1000° – 1500° F.
Kiln Controller – Mechanical or computer controlled device used to control and maintain kiln temperature for firing paints and glazes and annealing glass.
Kiln Setter – A mechanical tool using a pyrometric cone to shut off kiln at predetermined temperatures.
Kiln Shelves – Flat alumina, mullite or high temperature ceramic fiberboard shelves used to maintain a flat surface under the glass during firing.
Kiln Wash – A separator used to prevent glass from sticking to the shelf or picking up imperfections from the firing surface. A 50/50 mix of kaolin and alumina hydrate in aqueous solution of approximately 1 part dry mix to 5 parts water.
Kite – Smaller opening in tracery.
Knapping – Chipping the face or backside of Dalle de Verre or slab glass with a carbide tipped hammer to intentionally create conchoidal fractures to add sparkle or brilliance.
Lancet – Narrow, sharply pointed opening either as a stand-alone opening or a series of openings with tracery above.
Lancet Window – Narrow, sharply pointed window without tracery
Laminated Glass – Two layers of glass bonded together with a transparent polyvinyl butyl inner layer to keep the glass from coming apart when broken. Often used in storm windows and protective glazing systems.
Lamp Black – An amorphous form of carbon made from incompletely burned organic matter.
Lap Joint – (stacked joint, slip joint) Connection between two panels with the bottom panel finished with a “U” channel and the panel above finished with a “H” channel where the “H” slides overtop the “U” yielding a line similar in weight those surrounding. Often used in tracery to subdivide panels to facilitate installation.
Lateral Movement – The expansion of glass in a kiln when two or more layers are heated to fusing temperatures.
Lateral Shrinkage – The shrinkage of glass when cooling after being heated to fusing temperatures.
Lathekin – (fid) Wood, plastic or Teflon device used to manipulate lead around glass or to open leafs to accept thicker glass.
Lattimo – (lace glass) Venetian glass with alternate bands of opaque glass drawn in a wave patterns across clear glass.
Lavender Oil – A drying inhibitor for glass paints. Most often used to make extremely smooth mattes, especially with transparent enamels.
Lead – A lustrous, silvery metal with a melting point of 620° F. that tarnishes in the presence of air to a dull blue-gray. Its ductile qualities make it ideal for assembling stained glass windows.
Lead Came – (calme) Metal strips used between the pieces of glass when assembling stained glass windows. Comes in many shapes and weights and several alloys.
Lead Dike – Came cutting tool similar to diagonal gutters but designed to flush cut.
Lead Heart – The section of lead came that separates the top and bottom leaf. Can be thicker to add strength or taller to accept thicker glass.
Lead Knife – Traditional curved bladed tool used for cutting lead to proper shape and size during the assembly of stained glass windows. May be weighed to aide in cutting came with a hard tipped handle for setting glazing nails.
Lead Line – Indication on the cartoon or cutline showing the divisions between the glass and where the lead came will go.
Lead Vice – A tool mounted on a bench that holds one end of the strip of lead came allowing it to be stretched.
Leaf – The rounded, flat, shaped, or embossed portions of the came that are exposed in a finished window and connected by the heart.
Lehr – Tunnel like annealing chamber with conveyor system that controls the rate of cool down of newly made glass.
Leaded Lights – Clear glass windows made with cut pieces of glass separated with lead came.
Levelers – Ladder or scaffolding height adjusters used on uneven ground.
Lexan® – Polycarbonate material used as a durable protective glazing or storm window material. Filters UV rays but depending on exposure will yellow in relatively short periods of time.
Light – Opening for a single pane or panel of glass. Windows can be made up of several lights each with its own panel or pane.
Light Table – Clear or frosted glass topped worktable that allows light to be projected or reflected up through the surface and ultimately through materials resting on top. Used primarily for checking color and painting on glass.
Linseed Oil, Boiled – Made from the seeds of the flax plant and is used as a drying component in window cement, paints and inks. Exposure to oxygen causes it form a tough, clear, waterproof, flexible film.
Liver of Sulfur – (potassium sulfide or polysulfide) Used in a water solution to darken or patina zinc and other metals.
Luminescence – The act of giving off light other than transmitted or incandescence. Glass that glows with reflected light is said to have luminescence.
Lunette – Semicircular transom window.
Lustres – Metallic, iridescent surface decoration used both on glass and ceramics. Four primary families exist: Bright Metals, Iridescent, Colors, and Halos. Developed in Persia in the 9th century.
Mahl Stick – (maul) A hand rest typically with a padded end used to steady the hand or bridge an already painted area when working on an easel or light table.
Mandoria – Yellow or gold circle around the heads of saints representing heavenly light.
Marver – Thick polished steel plate used by glass blowers to cool and shape the hot glass. Also used as a surface from which to pick up frit or colored glass powders. Sometimes made from marble or graphite.
Matting – Shaded tones painted on glass after or sometimes before trace lines.
Mature Fire – Bringing glass to the full temperature to properly do the work expected, as in fully firing paint or completely slumping glass into a mold.
Mechanical Fastener – Devices used to affix glass into a frame. Carpet tacks, glazier’s points and sash clips are examples.
Medallion Window – Symbols or figures surrounded by a defined border superimposed on a field. Can be one or many stacked upon one another.
Medium – A water or oil based liquid used to mix powdered paints to a consistency needed for the intended application.
Medieval Style – Turn of the century American style of designing windows to imitate the aging cathedrals France and England.
Megalography – Designs on a mammoth scale.
Metal – Molten Glass
Metallic Lusters – A thin metallic coating painted onto glass or ceramics and fired.
Metaling – Reflective mirror like surface that develops from improperly fired silver stain. Can be removed with acid.
Mica – Transparent, sheet like, natural mineral that is unaffected by heat.
Milk Glass – Translucent white that transmits gold or yellow light, made with salt as an opacifier.
Mirror – Reflective opaque coated glass.
Mortar – Traditionally made of white Portland cement, hydrated lime, and sand and is used to set or point stone and sometimes set stained glass into stone frames.
Mosaic Diaper – Small pieces of leaded glass forming a regular pattern used as a border or background field, often assembled by apprentices.
Moyen – Form or reminiscent of the Middle Ages. See Medieval Style.
MSDS – Manufactures Safety Data Sheet sometimes referred to as Product Safety Data Sheet.
Muff Glass – Older English term referring to blown glass. See antique glass.
Muffle – Furnace or kiln used to enclose a gas flame.
Muller – Flat-bottomed glass grinding tool used much like a mortar and pestle, but on top of a plate glass to grind coarse glass paints.
Mullion – Vertical sash section made of wood, metal or stone acting as a structural division between panels.
Muntin – Horizontal division between window panels.
Muriatic Acid – (Hydrochloric Acid) a water solution of Hydrogen Chloride, HCL, added to copper sulfate solution to produce a darker patina on lead and solder.
Murrini Canes – Composed of small strips of glass fused into a block and stretched to produce a smaller though identical cross section.
Mushroom – Cement seeping between two layers of glass.
Narthex – Western arcaded porch section of a church, leading into the nave.
Nave – Center main seating section of a church. Often flanked by side aisles of lower height.
Neodymium – A silver white metal that is used in colored glass for astronomical lenses. Lasers, and UV protective eyewear.
Neon – Neon glass emits a characteristic intense reddish orange glow in a vacuum discharge tube.
Nimbus – Usually circular design element surrounding the head of sacred parsonages as a symbol of glory.
Norman Slab Glass – (bottle glass) A glass blown into a rectangular box mold measuring roughly 7” X 7” X 12” originally made in England.
Obscure Glass – Non-transparent glass resulting from etching, painting, the effects of chemistry, pollution, age, or texture.
Obsidian – Naturally occurring volcanic glass. Often black but can be found in brown, red, and green.
Occhio Window – Eye shaped opening, without tracery, that contains a single image or concept.
Oculus – Denotes a circular opening in the center of a dome, or in a wall without tracery or filigree. A feature of Byzantine and Neo Classical architecture.
Pate de Verre – 18th century French technique of crushed glass mold casting.
Patera – Circular or oval design element with geometrical rayed or leaf pattern, named after a Roman shallow drinking bowl.
Patina – Discoloration of metal due to age. May be natural or artificial.
Pattern Paper – Heavy 120# stock used to create durable patterns.
Pattern Shears – Three bladed scissors used to cut patterns that removes a space between adjacent patterns to allow for the thickness of the heart of lead came.
Pearling – Dot like bands of clear or light colored glass painted glass. Used to reduce halation.
Peep Hole – Opening in the side or top of a kiln to monitor painted glass for proper firing.
Pencil Bevel – Thin beveled glass shape with the top edges of the beveled sides coming together without a flat surface.
Perpendicular Style Window – Tall wide windows in English Gothic churches with perpendicular lines throughout tracery. Found in the last stage of Gothic architecture following the decorated period.
Photo Glass – Sheet window glass with a slight matt finish to eliminate reflections from the top surface.
Pickling – Cleaning metal by placing in a warm acid solution.
Plaster of Paris – A white, water setting casting plaster made from gypsum. Sometimes used as a filler in glazing cement.
Plate Glass – Clear glass greater than 1/8” thick. Used as a protective glazing or storm window material.
Plating – Two or more layers of glass inserted in a single lead came or mounted on an area of a panel to adjust color, shade or create other unique effects.
Pleochroism – Displaying different as viewed from different angles.
Plexiglas – Acrylic used as a durable protective covering or storm windows. Surface is prone to degrade with exposure but remains semi-clear with age.
Plique-a-jour – Jewelry technique with a stained glass look, made by filling a fine metal framework with transparent or translucent enamels and heating in a kiln.
Point Driver – Tool used to insert glaziers’ points into wood sash to hold glass in place prior to face glazing.
Pointing – Adding missing or replacing existing mortar between brick or stone.
Polarized Lens – Stress detection device used with one lens stacked on another with one lens rotated 90° from the other to check glass compatibility in fusing.
Polycarbonate – Plastic sheeting used to protect stained glass windows. Material is UV filtering but degrades with exposure to a translucent brown-amber color.
Pontil – Solid iron or steel rod used to manipulate hot glass objects off the blowpipe.
Pot – Crucible used to contain molten glass in a furnace.
Pot Furnace – Glass melting furnace with one or more crucibles.
Pot Metal Glass – Hand blown glass, melted in crucibles (pots), the traditional European glass used in stained glass windows. See antique glass.
Pouncing – A method of transferring a design from a drawing to another surface by pricking small holes in the paper with a perforated wheel or around the outline of a template using chalk dust, charcoal or whiting by dabbing the drawing and leaving the design on the second surface.
Predella – The vertical face or back of the altar or of the steps leading to the altar.
Pressed Glass – Molten glass pressed into a mold to make shapes or patterned textures. Jewels are a classic example of pressed glass.
Pressure Pot – Tank with abrasive material and compressed air used in sandblasting or abrasive etching.
Primary Colors – Reflectively seen as red, yellow, blue with black and white are mixed to produce hues and tones. Red, blue and green are the primary colors that when mixed together make white light.
Product Safety Data Sheet – (MSDS) Manufacturers sheet indicating the chemical make up of the product, safety guidelines, and all pertinent information for the use and cleanup of the product.
Programmable Kiln Controller – Electronic, computerized temperature controlling device with ramp, soak, and shut off stages used to control all aspects of the firing process to all proper annealing.
Protective Covering – Storm windows or outer covering installed on the exterior of a stained glass window to protect it from vandalism. Commonly constructed from plate or laminated safety plate glass, Plexiglas, or Lexan.
Pumice – Volcanic dust used as a polishing compound with a cork wheel to smooth glass.
Putty – Glazing compound used to set glass or panels into sash. Made from boiled linseed oil and whiting.
Pyrex – A high melting point glass that is resistant to temperature shock during quick cooling.
Pyrometer – Device used to indicate the temperature inside a kiln by measuring the resistance in a thermocouple.
Quad – Small unseen lead spacer used to fill space in heart required for undersized or thin glass.
Quarries – A simple repeating shape background field such as diamonds, rectangles, roundels etc.
Quarter Round – Finish molding with a quarter circle cross section sometimes used as a finish molding.
Quenched Glass – Hot glass that has been cooled quickly in water to form frit or finely broken glass. Quenched glass has a higher melting temperature than crushed glass.
Quill Work – Scratching into the dry but unfired glass paints and stains in order to shade, add detail, or otherwise alter the applied paints and stained before firing.
Rabbet – Section of the sash designed to receive the glass.
Radium – Glass texture similar to hammered made of regularly spaced domed bumps.
Rail – Horizontal top or bottom of a wooden sash or horizontal frame component.
Raking – Higher temperature glass effect achieved by pulling a pointed steel rod across the molten surface of the glass.
Ramp – The gradual increases or decreases in kiln temperature used to anneal or preserve annealing
Range Controller – High Temperature rheostat used to adjust the electrical power, and the heat, in an electric kiln.
Reamy Glass Texture – Antique glass with striations of thicker glass, also called cords. Made by using dissimilar melting temperature glass.
Red Lead – Lead tetroxide used in window cement, glazing putty, and paint to provide a primary coating of oxidation and protection.
Reduction – Oxygen poor environment found in glass kilns or furnaces when more gas is added to the flame (yellow flame). Can be created in electric kilns with mothballs.
Reeded – Glass texture consisting of parallel convex ridges. The inverse of fluted.
Reflected Color – The visible surface color viewed without light being transmitted through the glass.
Refraction – Distortion caused by the passage of light through a transparent material.
Refractory – Materials with a high point of fusion, used as kiln and glass blowing equipment and insulation. Firebrick, soft brick, fiber blanket are refractory materials.
Reglet – Groove in stone or wood into which the window is installed.
Renaissance – The new direction in art from the 14th century. First a revival of Roman and Greek ideas, later a consuming desire for knowledge for its own sake. The beginning of the departure from faith to science.
Rendering – Scale colored design used to present an idea. The first step to creating a stained glass window.
Repair (Window) – to mend a broken area such as a window that has be vandalized or damaged due to impact.
Resist – Thin adhesive backed film used to protect the surface of the glass from the effects of acid, abrasive etching or the effects of cementing.
Respirator – Facemask used to filter out dust, vapor or fumes.
Restoration Glass – Blown transparent glass with small seeds, bird’s eyes and other subtle imperfections used to mimic window glass in older buildings.
Restoration (Windows) – The process of returning a window to a structural condition equal to new, and an aesthetic condition to as close to new as modern conservation principals allow. See repair and conservation.
Restrip – Thin metal strip inserted between the glass and heart of the lead to increase strength. Usually found on vertical through lines.
Retable – A raised shelf above the altar for placing the altar cross, flowers, or other sacred items.
Reticulate – Designs made of squares with intersecting lines.
Retreating Colors – Colors that appear retreat into the background such a blues and other cool colors.
Rheostat – Used to control the temperature of a soldering iron to maintain a constant temperature for producing uniform solder joints.
Rhine – Thicker edge of a sheet of blown or hand rolled glass. Usually cut off before the sheet is cut into small pieces.
Rigidizer – Hardener used with refractory fiberboard or blanket to conform it to a shape or mold.
Ring Mold – Glass slumping refractory similar to a kiln shelf with a round hole in the center used for bending sheet glass into the shape of a bowl or vase.
Ring Mottled – Color/ texture found in Tiffany glass.
Ripple Glass Texture – Cathedral or opalescent glass texture in the form of regular tight waves with crests and valleys.
Romanesque Style – Pre Gothic style of stained glass and architecture dating from the 8th to 11th centuries with simpler designs minimal trace line painting. Few examples are know to exist with the best known being those at Augsburg Cathedral in Germany dating from he late 11th century.
Rondo – A circular design element of window.
Rood Screen – A cross bearing screen between the nave and chancel in a medieval church.
Rose Window – Round symmetrical Gothic church window first used in the 12th century in France. Consists of repeating petals, spokes or other decorative architectural details.
Roughing – First step in the beveling process the shapes the edge of the glass to a chamfer of less than 45°.
Rondel – Spun flat or plate like, round sheets of glass measuring from 2” to 24” in diameter with a distinct pontil mark in the center.
Rubbing – The process of creating an imprint of the lead came of an existing window on to paper or other material.
Running Pliers – Glass breaking tool used to enable cracking, most often used for breaking long straight lines.
Safety Glass – Laminated or tempered glass that will not break into sharp shards. Used in doors or within 18” of a door or floor.
Saddle Bar – Generic name for older rebar, typically round iron or steel, and engaged into the sash or frame. Copper tie wires that are soldered to the stained glass panel during fabrication are wrapped around the rebar and twisted off to help support the panel.
Sagging – Bending glass in a kiln. See slumping.
Sash Set – (rabbet) The difference between the daylight or sight size and the maximum window size divided by two.
Satin Etch – Glass enamel that closely resembles the effect of acid or abrasive etching.
Saturation – The vividness and intensity of color, the less white added the less saturation.
Scrubs – Glass painter’s brushes used to create highlights by removing paint after it is dried.
Secondary Colors – Orange, green, purple made from combining primary colors.
Seeds – Gas pockets inside the glass. Adds sparkle as light passes through the glass.
Semi Antique Glass – Machine made glass that resembles antique glass striations but without seeds or shading. GNA FMA
Set Point Controller – A smart pyrometer like device that will automatically hold the kiln at a constant temperature or shut it off.
Setting Block – A flat wood, rubber, vinyl or plastic block of varying thickness used to center or align the panel in the opening.
Shade – The dark or light degree of color.
Sheet Warpage – Non-flat glass, resulting from internal stress or irregular manufacturing.
Side Light – Windows beside an entry or door.
Silica Flower – Finely ground glass used as a base for glazes and glass paints as well as an ingredient in glass casting molds.
Silica Gel – A desiccant or drying agent used to remove moisture from the air. Amorphous and highly absorbent. Used in glue chipping to accelerate the final drying of the glue. Can be reused by heating to evaporate the absorbed water.
Silicon Carbide Abrasive – The most effective etching material when using compressed air.
Silk Screen – Image transfer system using a negative of the image as a mask on a screen that allows paint to pass through to the under lying glass.
Silhouette Lead Lines – Larger primary outline leads around a subject in a design.
Sill – Base of a window that slopes away from the building to aid water run off.
Silver Nitrate – Active ingredient in silver stain, some enamels, and iridescent formulas.
Silver Stain – A stain that is painted on the backside of the glass and fired to a temperature of 950° – 1100° F. to achieve a color range from bright yellow to orange to amber. Discovered in 1425 and used to embellish clear and colored glass since.
Simultaneous Contrast – Two colors, side by side, interact with one another and change our perception accordingly.
Sky Eye – Early English root for the word ‘window’.
Skylight – Window opening in the roof.
Slab Glass – See Dalle de Verre.
Smalti – Thin glass tile, made from opaque, colored glass and used to make mosaics.
Slumping – Bending glass over or into a mold at a temperature greater than 1100° but less than 1400°.
Soak – Maintaining the temperature of a kiln to mature paints or anneal glass.
Soak Tank – A container filled with warm water and mild detergent into which a panel is placed to soften the cement and aide in disassembly.
Soft Brick – Porous, pumice like insulating refractory product used to line kilns and glass blowing furnaces.
Softening Point – Temperature at which the glass begins to bend into a mold or pick up textures from the kiln shelf.
Solarization – Violet hue taken on by glass high in manganese that is exposed to sunlight for a long (decades) period of time.
Solder – Alloy made of (tin and lead with trace amounts of antimony, silver and other metals) with a lower melting temperature than either of the individual primary metals. Used to join the lead, zinc or copper came together. Most common alloy is 60/40 tin/lead.
Soldering – A method of joining metals together with solder and heat. Solder melts at a temperature that is lower than the metals that are being joined.
Spandrel – Triangular space between an arch and a rectangular border that encloses it.
Spontaneous Contrast – The effect of two powerful colors separated by a neutral gray, clear or white where the eye allows both colors to influence the neutral color between.
Spring clip – Mechanical fastener used to hold glass into sash prior to putty glazing or applying a molding
Springline – The point of a vertical side where an arch begins or springs from to form a smooth transition.
Squaring – Design technique used to convert a scale drawing to a full size drawing where a uniform scale grid is drawn on top of the scale drawing and a uniform full sized grid is drawn on the full sized drawing.
Squeegee Oil – A painting medium that is good for solid trace lines, designed for silk screening but can be hand painted by brush.
Squinch – Arch across the corner of a rectangular object turning it into a quarter-circle.
S.S. – Single strength glass. Window glass that is less than 1/8” thick.
Stained Glass – Objects composed of colored glass held together with metal creating deigns.
Stile – Vertical side of a wood sash or vertical element of a ‘stile and rail’ door.
Stone Lead – Lead came configured specifically for installing panels of glass into stone frames. Configured to look like a small ‘h’ where the single flange can be folded perpendicular to the panel until the panel is set into the closed stone groove, then folded back parallel to mechanically engage the panel.
Stool – Inside sill at base of window casement.
Stipple Brushes – Glass painting brush used to highlight, texture, and remove matt areas after the paint has dried.
Stippling – Shading technique used in glass painting to produce small dots of light on a dark field by using the end of a badger or stippling brush on an unfired matt surface.
Stone – Small bit of refractory sometimes found in the glass from the manufacturing process.
Stopping In – Replacing broken glass without removing the panel and releading. Often used to repair single pieces that have been broken in relatively new windows.
Stopping Knife – Customized tool with a blunt end and offset shaft bent to about 30° used to apply lateral pressure on lead when glazing.
Strain Point – Temperature at which glass release internal stress. Lower end of the annealing range.
Strapwork – Interlaced banding in window borders forming geometric designs.
Streaky Glass – Glass with streak like variations in color or several colors mixed together. Made in antique, cathedral and opalescent glasses.
Stress – Incompatible or poorly annealed glass with internal tension.
Striations – Surface depressions resembling clean scratch like gouges on the outside surface of antique sheet glass that add sparkle to the transmitted light.
Striking – Changing the color of a glass by reheating, sometimes intended, as in striking a gold ruby, other times unwanted as in colors changing when heated to fire glass paint or slump.
Stringers – Thin 1/16” – 1/32” diameter straight strings of compatible glass used in fusing.
Strip Cutter – Tool used to gauge cut uniformly wide strips.
Sweat Soldering – To attach two pieces of metal that have been pre-tinned using indirect heat without flux. Useful for attaching plates or laminated layers to a window.
T Bar – A ‘T’ shaped steel, iron, bronze or aluminum used to subdivide a window opening into smaller more structurally sound sections.
Tack Fused – Attaching or combining 2 or more pieces of compatible glass together at the lowest possible temperature without changing the shape of the original pieces.
Tack Soldered – To temporarily hold lead, zinc, copper foil, or other metal together before final soldering.
Tallow Fluxes – Made from sheep or beef and containing oleic, palmitic and steric acid and supplied in the form of a wickless candle. It makes a good non-toxic flux.
Tektite – Dark Green to black naturally formed glass that is formed from terrestrial debris ejected during extraterrestrial impacts.
Tempered Glass – Hardened glass that can be as much as 5X stronger than un-tempered glass of equal thickness. Considered safety glass because of its unique quality to disintegrate into small “pea-gravel” size pieces with round almost blunt edges.
Template – A full sized paper or cardboard pattern used to reproduce a something.
Tesserae – Square glass, stone wood or ivory mosaic tile used on floors and walls.
Texture – A specific uniform repeating surface other than smooth typically on one side of machine rolled glass. Also occurs on antique glass but is not well defined or uniform.
Thermal Break – Polyurethane gasket between the interior and exterior surfaces of aluminum extrusions to reduce heat transfer and prevents excessive condensation from forming on the interior surface of the extrusions in extreme cold weather.
Thermal Shock – Glass that has been cooled quickly and as a result retains internal stress that will cause random breakage.
Thermocouple – The bimetallic sensor used with a pyrometer to control kiln temperature.
Thin Glass – ±1/16” thick glass often referred to as SS or Single Strength if window glass.
Tie Wires – 14 gauge copper wire soldered to the surface of a stained glass window used to attach the panel to the reinforcing bars.
Tin – A solid metal used to lower the melting temperature of the lead in solder.
Tinning – To coat a surface with a thin layer of solder.
Tooth – The type of surface left on glass after acid or abrasive etching.
Trace Line – Opaque to semi-opaque painted line on a piece of glass to delineate a design or design element.
Tracery – Frame members forming irregular shaped but mostly symmetrical panel openings in Gothic architecture. Usually found above two or more lancets, but can comprise the entire opening in the case of circular windows. See rose windows.
Tracing Brush – Long soft and pointed brush that allows a long line or brush stroke with a single pull. Often made from red sable or squirrel hair.
Transept – Section of the church that is perpendicular to the nave that separates the nave from the chancel.
Transite – Hard and brittle sheet made of cement and asbestos used to clad the exterior of a kiln.
Transitional Style – The architectural change in English style between Norman and Old English.
Translucent Glass – Obscures sight but allows some transmitted light.
Transmitted Light – The light after it passes through the glass.
Transom Window – Smaller glazed opening above a door or larger windows.
Transparent Enamels – Low temperature glass paint that fire into the glass that does not block the transmitted light through the glass but alters the color.
Triad – A set of three like openings, colors or other objects.
Trichromatic Pallet – A color composition made up of red blue and yellow, from which the eye can create the full spectrum of colors.
Tri-Sodium Phosphate (TSP) – A phosphate based cleaning compound that tends to neutralize lead.
Triple Glazed Glass Units – Insulated glass units with a stained glass panel between the layers of clear glass.
Turpentine – A clear, volatile, hydrocarbon fluid that will not mix with water. Derived from living pine trees. Used as a paint medium for air brushing and in cement.
Tympanum – A triangular or semi-circular shaped decorative wall surface above an entrance, bounded on the bottom by a lintel and an arch or arches above.
U Lead or Zinc – Metal formed in the shape of a ‘U’ used to border sections of a window or on the top of the bottom panel in a lap joint configuration.
Ultraviolet Glue – Clear adhesive that cures with the presence of ultraviolet light.
Ultraviolet Lamp – Short-wave ultraviolet emitting light used to cure ultraviolet adhesives and to determine the tin coated side of float glass.
Under Fired – Painted glass that is heated to a temperature that is less than what is needed to fully fuse the paint to the glass.
Uprising – Bubbles formed by escaping gasses from the kiln wash, kiln shelf, or the glass itself when glass is over fired.
Value – Lightness or darkness of a color that is controlled by the addition of black or white.
Vehicle – Oils or other liquids used to allow powdered glass paints to be become liquid and paintable.
Vent Hole – Opening in protective covering placed over top of a stained glass window to allow for temperature, pressure, and humidity equalization.
Vent Plug – Screen or filler used to prevent insects from entering the space between protective covering and stained glass.
Ventilator – An operable panel in a stained glass window to facilitate fresh exterior airflow into the building. Usually found at the base of the window but can be found at various levels.
Vermiculite – Expanded mica used as an insulator or casting refractory additive with insulating qualities.
Vesica Shaped – Enclosed design element with curved sides and pointed top and bottom.
Victorian Style – 19th century design style with ornate, flowery patterned symmetrical designs
Vitreous – Made of or looking like glass.
Warm Glass – Term used to describe kiln worked glass painting, fusing and slumping.
Waldglas – A type of glass made with potash during the Middle Ages in northern Europe. Often yellow, green or brown, depending on impurities. Not a durable glass due to its weak chemical composition.
Wash – Thin coating of paint used to tone down the light transmission through glass, create shadows etc.…
Water Glass – A glass painting media (sodium silicate) that provides fast drying wash. Several layers can be applied before firing. Hard on brushes due to quick drying.
Water Jet – A tool used to cut glass using high-pressure water mixed with abrasives. Often CNC controlled.
Wax – Used to attach cut pieces of glass to clear glass easels for painting in natural light.
White Lead – Lead carbonate, used in ceramic glazes and old lead based paints.
Whiting – Calcium Carbonate used for covering kiln shelves, as filler in cement, and to clean and polish glass.
Whipping – Drying paint by fanning.
Wispy – Cathedral sheet glass with subtle streaks of color or opal or both.
Working Range – The temperature range required to perform the intended task or process.
Woven Leading – A method of glazing geometric backgrounds to add strength by minimizes thru or continuous or unbroken lines.
X-acto Knife – Versatile small handles cutting tool with a wide range of interchangeable blades. Sometime referred to as a hobby knife.
Y Lead or Zinc – Border metal shaped like the letter ‘Y’ sometimes used instead of the standard ‘H’ lead.
Z Bar – Metal sash bar with two opposing right angles with a common flat connecting side.
Zinc – A bluish white rigid metal used in place of lead.
Zinc Bender – A three-roller tool that allows uniform smooth curves to be created in harder metals.
Zinc Came – Channels made from zinc used to assemble panels. Often used to assemble beveled glass panels or in doors and sidelights due to it increased rigidity and strength.
Zinc Chloride Flux – Aggressive chloride based flux best suited for soldering old zinc. Often used to solder round and semi-round lead.
Zinc Saw – Small tabletop saw with a fine toothed blade used to cut zinc, brass crown jacketed lead, or heavy leads. Can be set up to gauge cut many pieces of equal length for increased production of similar panels.
Zipper Cut – Cut and polished repeating scalloped border on a beveled piece of glass.