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Conservation And Preservation Of Stained Glass Nationwide
ACID-ETCHIN
Process of removing colored flashing. The area of flashing to be removed is first outlined. The rest is masked with bituminous paint, while hydrofluoric acid eats through the exposed portion to the paler-colored layer below.
ANTIQUE GLASS
Colored, mouth-blown sheet glass of the type used in medieval church windows. Such glass (now called full antique) continues to be made today. The colors are crisp, and the interior variegations are desirable for their irregular light refraction. Antique glass is traditionally used in the best-quality church windows. In the United States it has been used very selectively in residential work.
ARABESQUE
A complex curvilinear pattern found in Renaissance decoration that is often composed of floral and vine motifs. It has antecedents in Islamic architecture.
ART GLASS
Usually refers to turn-of-the-century windows made with opalescent glass because the multicolored variegation within the glass could be used to create painterly effects. The term art glass was actually in use before opalescent windows became popular.
BAPTISTERY
Part of a church, or adjacent building, used for baptisms.
BAY WINDOWS
A usually curved or three-sided window that projects from the ground floor of a building. Decorative glass is often found in the transoms or upper sash of bay windows.
BENDING OF PROTECTIVE GLAZING FRAME
Conforming the extrusions (usually aluminium)dividing the protective glazing panels to match the existing mullions and muntins (divider bars) of the stained glass window that the exterior glazing will cover. This construction method produces a highly desirable aesthetic appearance and minimizes shadows over the stained glass window, thus maximizing the visibility of the window design.
BEVELED GLASS
Plate glass that has its edges ground and polished to an angle. The nineteenth- century beveling process had four steps: (1) rough grinding on a cast-iron "mill" with sand and water; (2) smoothing on a sandstone wheel; (3) polishing on a wooden wheel with fine pumice; and (4) brilliant polishing on a felt wheel with ferrous oxide. Beveled mosaics were usually set in zinc or brass cames.
BRACE, LOOSE
A reinforcing bar (usually flat or round in shape) that has separated from the stained glass panels. Repair consists of either re-soldering the flat bars onto the stained glass panels, or in the case of the round bars, soldering new copper wires onto the stained glass panels that tie across and are also soldered into the existing round bars.
BROKEN GLASS
A piece of glass that has a hole in it or is completely broken out.
BULGE
A bulge is a section of the window that has become so weak that the lead and the glass protrudes in or out from an inch to a foot. If this condition is allowed to remain unchecked, it will break the glass, the lead joints, and eventually the whole section is in danger of falling out or blowing in.
CAMES
The strips of metal that are used to hold together glass mosaics. Derived from the Greek word for reeds (kalmus), which in the Middle Ages were bound together and used as crude forms for casting lead. Cames are found in many shapes and sizes and have been made from lead, zinc, brass, pewter, and German silver.
CARTOON
The full-scale drawing from which the individual pieces of a stained-glass window are cut. Also used as a guide when the window is leaded up.
CATHEDRAL GLASS
Commercial, machine-rolled stained glass widely used in the United States.
CHANCEL
Classically, the eastern part of a church, reserved for clergy and containing the altar and choir.
CHOIR
Classically, the eastern part of a church in which the choristers sit, usually separated from the nave by a screen or rail; sometimes applied to the whole chancel.
CLERESTORY
Upper tier of a church, pierced with windows.
CRACKED GLASS
A piece of glass that has one or two straight cracks and is in no danger of falling out. (Usually cracked glass is cemented rather than replaced.)
DALLE DE VERRE
Pieces of glass, usually about one inch thick and often chipped or faceted on the surface, which are set into concrete or epoxy resin.
DIVIDER BAR
A mullion (vertical) or muntin horizontal) composed of wood, metal or stone dividing glass or protective glazing panels.
FACETED GLASS
see Dalle de verre
FLASHED GLASS
Glass made up of a thick base color and a micro-thin "flashed" layer of contrasting color. Red flashed on white (clear glass) is well known, but many other combinations are found, including blue on yellow. When the flashed layer is removed by etching or wheel-cutting, designs of contrasting colors are created.
FLOTE GLASS (1/4)
Regular clear glass 1/4 inch thick. Glass has a clear, crisp look and is easily washed. Not for high vandalism areas.
FOIL
Small arc opening in Gothic tracery; the number of foils is indicated by a prefix-- trefoil (three), quatrefoil (four), cinquefoil (five).
FRAME PAINTING PROCEDURES
Window frames and sashes are prepared and painted according to the following specifications:

  • Prepare the exterior window frame and sash surface by standard scraping to remove loose paint.
  • Re-caulk the prepared frame and sash
  • Repaint the prepared surface with one coat of primer and one coat of premium quality paint (or two coats as required, to be determined by authorized project supervisor) in the church's choice of color.
FRAME DOUBLE-GLAZED
A frame designed to secure two glazing surfaces to wall structure (may contain stained glass and protective glazing).
FRAME SINGLE-GLAZED
A frame designed to secure one glazing surface to wali structure (may contain stained glass or protective glazing).
FRAME THERMO-BARRIER
A frame that is designed such that the interior metal channel (containing the stained glass) is separated from the exterior metal channel (containing insulated thermopane glass) by a layer of thermal insulation, reducing heat transfer and correspondingly increasing R-value.
FUSED GLASS
Pieces of colored glass bonded to a sheet of glass by heat.
GEORGIAN ARCHITECTURE
Buildings constructed between the reign of George I (1713) and George III (1830). The dominant theme was Neo-Classicism, with an emphasis on Palladian interpretations.
GLUE-CHIP GLASS
Clear or colored glass that has a frost-like surface. Produced by coating glass with animal-hide glue that is heated and then shrinks, taking off slivers of glass.
GOTHIC
Style of architecture, dating from the mid-twelfth century, generally associated with the pointed arch, the flying buttress and the rib vault.
GROZING
Biting away the edge of a piece of glass with pliers.
HEADER
A metal cap spanning the air space between the sill of the ventilator frame (usually the top sill) and the horizontal divider bar that separates the protective glazing panels (commonly used in conjunction with outset method of protective glazing framing).
INDUSTREX (3/16)
3/16 inch thick glass with an obstruct finish or diffusing texture.
JEWEL
Smooth, faceted, pressed, or chipped pieces of glass usually made to imitate precious stones. Prolific use of these decorative inserts is a hallmark of American windows of the 1880's and 1890's. The jewels were made in all shapes and sizes, were frequently set in clusters or strung out as festoons, and were occasionally cast in figural forms.
LEAD CAME
The grooved metal that surrounds each piece of glass in the window to hold the glass in place and to complement the design of the window.
LEADED GLASS
Specifically, pieces of glass held together in a web of lead cames. Generally refers to very simple mosaic patterns glazed only with clear glass.
LEXAN XL- 1
Polycarbonate sheet which is virtually unbreakable. This product has been specially coated to avoid yellowing. Good for high vandalism areas.
MATTE
Muted, uniform finish.
MATTE-LITE (LEXAN SL-2230)
Same properties as regular XL Lexan, but has non-glare finish. (Only available in 3/16 inches thickness.)
MEDALLION WINDOW
A decorative window, usually of leaded glass, in the center of which is a circular panel on which a figure, scene, or significant symbol has been painted.
MOSAIC CONSTRUCTION
Decorative windows comprising many pieces of glass, each cut separately, and usually held together within a network of metal came. Can refer to leaded glass, beveled glass, mercury mosaics, and complex designs set in wooden mullions.
MULLION
Specifically, the heavy, vertical supporting member that separates the openings of a multi-light window. Often made of masonry and well defined in traceried lights. Generally, however, "mullion" has come to mean the thin wood molding (both horizontal and vertical) that separate the glass in a multi-paned sash.
MUNTIN
A vertical member that separates the panels in a door. Also, the vertical molding that separates the glass in a multi-paned light.
NARTHEX
Western arcaded porch, or vestibule, of Early Christian and some later Basilican churches.
NAVE
Main part or central aisle of a church, extending from the entrance to the transepts of the choir.
OPALESCENT GLASS
Glass with opaque, variegated colors, in which light is held and refracted internally. Also referred to as "art glass" and "American glass." Considered the antithesis of antique glass (pot metal), it was denounced by traditional religious window artists. Produced and used primarily in America, it is found in both secular and ecclesiastical buildings.
PAINTED GLASS
Painted glass is either colored stained glass with painted highlights or shading using a black tracing paint which is basically ground glass that is intermixed with water or venetian turpentine to a poster color consistency. The other type of painted glass is basically clear glass painted with special ceramic enamels using the desired colors. Once this glass is painted, it must be fired in a kiln to a temperature of 1200 degrees so the paint, which is actually ground glass, can fuse itself to the glass and become a part of the glass itself. Any piece of glass with a design or figure on it is considered painted glass. Each color requires a separate firing.
PERIMETER BAR
An F-shaped metal bar, usually composed of aluminum, that serves as the perimeter frame for protective glazing.
PLATE GLASS
Machine-made glass that has been ground and polished so that it is free from flaws and distortions. It is usually at least 1/4 inch thick and is used primarily for bevels, mirrors, and large store windows. Until the early twentieth century, polished plate was optically much clearer than standard window glass.
PLEXIGLAS (1/4)
1/4 inch thick polyacrylic glazing sheet. Plexiglas is sixty times more break resistant than glass and non-yellowing.
RECEMENTING
Recementing consists of brushing a special glass cement into every lead came between the lead and the glass in the entire window. This will hold the glass firmly in the lead, seal the minor cracked glass and small holes between the glass and the lead where the light shows through, strengthen the window throughout and help to waterproof it.
RELEADING (TOTAL)
Releading consists of removing the window from its frame, taking the window apart piece by piece, completely rebuilding the window with new lead, recementing the window on both sides, installing new steel reinforcing braces and installing the window back into the frame.
ROSETTE
A small ornament cast in lead and used to cover the solder joint where several cames converge. Used often in the Georgian and Federal periods, and later, in the nineteenth-century Neo-Classical buildings.
ROUND- HEADED
A window or door that forms an arched opening, Traditionally used for the center light of a Palladian window.
SASH
Wood or metal framing that holds the window glass. Double-hung sash slides up and down. Casement sash is framed in permanently or hinged to swing open.
SEALANT, SILPRUF
A deluxe, versatile sealant, manufactured by General Electric, that adheres to stone, masonry, metal, plastics, wood, steel, glass and other materials. Silpruf sealant is the ultimate in sealant that is used in place of caulking or putty. While caulking or putty will harden and chip away, allowing water to leak through, G. E. sealant will remain elastic and will not crack or peel due to heat, cold, expansion, contraction, vibration or any form of moisture. This sealant is used primarily for protective glazing installations.
SHATTERED GLASS
A piece of glass that has multiple cracks that cross or meet and is in danger of falling out.
SILVER STAIN
The clear solution of silver nitrate that is applied to glass on the opposite side from any painted detail. It is usually fired separately and turns various shades of yellow. This phenomenon is the basis for the term "stained glass."
SLAB GLASS
see DaIle de verre
SOLDER
A mixture of tin and lead, which for glass workers is manufactured to melt around 400 degrees Fahrenheight. After leading up, all the cames of a mosaic window are joined with a thin layer of solder.
SQUARE- HEADED
A door or window opening that is rectangular.
STAINED GLASS
Traditionally, leaded mosaic windows of colored glass that have also been painted and fired, with or without the additional application of silver stain. The term has come to represent any mosaic window, with or without paint or stain, composed of glass that is colored or clear.
STEEL REINFORCING BRACE
It is a galvanized or cold rolled flat steel bar that is set edgewise against the window and runs horizontally across it. It is embedded into the frame at both ends and soldered to the window at every lead joint to securely anchor the window in place and to reinforce the window where it has been weakened by bulging or in need of additional bracing to strengthen the window.
STREAKY GLASS
Glass in which the color appears as streaks, rather than being uniformly dispersed.
SUPPORT BARS
Iron bars that are fastened to the inside of mosaic window and door panels to help support the weight of the glass and the metal cames.
T-BAR
A T-shaped steel or aluminum bar that divides the stained glass or exterior glazing panels, which transfers the weight of the panels to the jambs.
TEMPLATE
Full-size paper or card pattern of a window; also piece of tracing paper or card used, particularly in France and Germany, as a pattern around which glass is cut out.
TERRA-COTTA
Unglazed, fired clay used extensively in late nineteenth-century American building. It is found in reds and yellows and was often sculpted into ornate figures and patterns.
TRACERY
Ornamental stonework in the upper part of a Gothic window. PLATE tracery: the earliest, most elementary form, in which simple shapes are cut out of the stonework; BAR tracery: thirteenth-century development in which patterns are formed by thin stone ribs; GEOMETRIC tracery: earliest form of bar tracery distinguished by symmetrical shapes; FLOWING tracing: more curvaceous, fourteenth-century style of bar tracery; FLAMBOYANT tracery: fifteenth-century French form characterized by flame-like curves; PERPENDICULAR tracery: comparatively sober style characterized by vertical lines which succeeded flowing in late fourteenth-century England. RECTILINEAR tracery: fifteenth-century development of Perpendicular characterized by a system of rectangular panels.
TRANSEPTS
Two projecting arms, usually between the nave and chancel, of a cruciform church.
TRANSITIONAL WINDOW
A decorative window in which the design incorporates motifs from a currently popular style and also elements from an incoming fashion. Often seen when flamboyant Renaissance window designs began to moderate into the more conservative Neo-Classical mode.
TRANSOM
The horizontal cross-member above a door or window opening. Also refers to the actual window that is placed in the transom area.
TREFOIL
see Foil
VENT OR VENTILATOR
A ventilator is the section of window that opens to allow ventilation in the building. There are two types of ventilators, single-glazed and double-glazed. A single-glazed ventilator positions the protective covering on the exterior side of the stained glass.
VENTILATOR DOME-GLAZED
A ventilator window with two glazing surfaces (stained glass with protective glazing, for example ).
VENTILATOR, SINGLE-GLAZED
A ventilator window with one glazing surface (may contain faceted glass, stained glass or plate glass).
WHEEL WINDOW
Round window in which the stone tracery radiates from the center like the spokes of a wheel.
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