Acid-Etching: A simplified process for the making of cameo glass. A vessel of two or more layers of cased glass has a design drawn on it, then part covered with a protective varnish. It is then immersed in hydrofluoric acid, which attacks the exposed parts and forms the pattern. Prolonged immersion deepens the design, while different parts of the vessel may be worked on by changing the position of the protective varnish. This technique creates the cameo design and may be finished by simply polishing or supplemented with wheel-carved details before the final polish. It is also used to block out the basic design for a more elaborate technique.
Annealing: The process of making a vessel involves a variety of procedures executed outside the kiln. The vessel at this stage risks cracking from internal stress caused by the uneven cooling of its various parts. Annealing involves heating the finished vessel, thus allowing it to cool slowly uniformly and safely. This process takes place in a lehr.
Appliqué: External relief glass decoration applied to the body of a vessel, such as trailed glass threads, blobs, pastilles, handles, etc.
Aventurine: Glass in which oxidized metallic particles are suspended, simulating aventurine quartz. The most common are gold aventurine, which has a brilliant brown color, and is flecked with copper particles; and green aventurine, where the color is produced with particles of chromium.
Batch: The mixture of silica, potash and metallic oxides ready to be put in the melting pot in the kiln, which when fused with the cullet, will eventually vitrify and become glass. Also known as Frit.
Berluze: A freely blown vase, the baggy body smooth a' soaped, leading to a tall, slender neck at least twice the height of the body. The surface was either smooth or granulated with acid, and was of a solid color or varied with abstract splashes of color. They were made by Daum Freres, and also by Muller Frères and other firms. Although some are quite small, many are impressively tall. Groups of these are particularly decorative.
Blank: A glass vessel completed, but not yet decorated.
Blow-Molded (or Mold-Blown): A vessel made by blowing the parson into a mold. Thus the outer surface acquired a three-dimensional decor, further enhanced by the judicious use of color in the parison. The vase could then be finished with some carving, or acid-etching, then polishing.
Bombé: A French word meaning convex or bulging.
Borax: A crystalline salt used in making certain types of glass. A certain amount is often added to the Batch to strengthen the glass. Pyrex, the heat-resistant oven-glass developed by the Corning Glass Works, and manufactured under its license worldwide, is made with borax.
Cabochon: A convex blob of glass applied to the side of the vessel for decoration. Sometimes made of colored glass cabochons are frequently found in clear glass carefully sited over a piece of metallic foil which appears to give it color. The term was originally used for unfacetted gemstones of such a shape.
Cameo Glass: Vessels of two or more cased layers of glass in which the outer layer (or layers) are carved or etched so as to leave a design in shallow relief in which various parts of differing thickness appear in the colors of the various layers.
Cased Glass: Vessels made of two or more layers of glass of different color.
Cathedral: GlassGlass sheets for manufacturing leaded glass windows and mosaics. Louis Comfort Tiffany maintained at least one cathedral glass shop in his glass-works, in which a dazzling variety of colors, textures and degrees of translucency was developed. In 1897 Cecilia Waern reported in The Studio that Tiffany maintained an available stock of 200 to 300 tons of cathedral glass.
Chine: Variegated, speckled or figured glass.
Cire Perdue: The French for 'Lost Wax'. This is a process in which a model is carved in wax then has a mold built up around it. When this is heated, the wax melts and runs out through small holes in the base of the mold, which is thus left with the exact contours of the original wax model. The mold can then be filled with molten glass or bronze which, on cooling, appears as an exact replica of its original model. Some molds are re-usable, others are destroyed when opened. René Lalique used this technique for his early glass. and Frederick Carder used it from 1933.
Cloisonné: An enameling process in which 'cloisons', thin metal partitions are shaped to the required pattern and enclose the enamel.
Cobalt Oxide: A metallic oxide used to color glass, producing a very wide range of blues, from pale shades to rich, dark ones.
Combed Decoration: A surface pattern produced by applying colored glass threads to the parison, then rolling it on the marver until the threads are on the same level as the surface of the Parison. Using steel claws, the colored glass threads are then dragged upwards and downwards to produce a variety of decorative effects, including festoons and feathers.
Crown Glass: Glass panes made by blowing a glass bubble, attaching it to a rod which is rotated after the bubble is cut so that it spreads and flattens into a disc. After annealing, it looks like a wide disc with a central raised boss from which the rod has been detached. The disc is then cut to the required shapes, the glass itself having a slightly wavy appearance.
Cullet: The starting point of the Batch. It consists of smashed glass and includes vessels which have gone wrong in the making, accidentally damaged glass, otherwise unwanted glass, and remnants discarded in the course of making a vessel. These are all smashed together, the ingredients required for the new glass are added, and the whole lot is melted together.
Diamond Point: An engraving technique in which the surface of the glass vessel is scratched with a diamond point, the diamond being an extremely hard substance capable of being faceted to sharp edges. This technique, requiring expert skill and patience, was largely superseded in the second half of the nineteenth century by the use of wheel-carving.
Diaphanous: A pellucid, limpid glass which allows light to penetrate, while not being actually transparent.
Diatreta: A vessel in which the main body is connected at rim and foot with an outer decorative layer, generally molded in openwork, it was originally cast by the Romans as a single entity. Tiffany and Frederick Carder at Steuben executed Diatreta vases in which the outer layer was fused to the body with glass struts.
Electrolier: A bracket or fitment, often elaborate, designed to support an electric lamp.
Emaux-Bijoux: Translucent enamels placed layer upon layer on a thin metallic base fused to the body of the vessel. These were developed by Emile Gallé to reproduce such things as a dragonfly’s bulbous eyes, or gemstones like opals.
Entrelacs: Interlaced ribbons derived from Celtic decoration as exemplified in The Book Of KeIls.
Etude: The term used by Gallé to describe vases which cracked, or were otherwise damaged during production, but which were of sufficient interest and importance to warrant their survival and sale. The word Etude’ is normally inscribed next to the Gallé signature, and in similar lettering. Damaged vessels not considered worth keeping as Etudes were smashed and added to the cullet.
Faience: A general term for earthenware.
Favrile: The Trade Mark registered by Louis Comfort Tiffany in 1894, it refers not only to the iridescent glass he manufactured, but also to his other creations, including ceramics, lamps and leaded glass windows. It is derived from ‘fabrile’, an Old English word indicating the product of a craftsman.
Feldspar: A variety of minerals found in igneous rocks. They consist mostly of silicates of aluminum combined with some other minerals, so they vary in their chemical composition, crystalline form and color.
Finial: The decorative terminal point of an object, particularly the lid, or cover and can be used as a handle.
Fire-Polishing: A technique for giving a vessel a smooth, highly polished surface. Once manufactured. the vessel might well have a rough surface on emerging from a mold, or a sharp outline as a result of acid-etching. Reheating the vessel at the glory hole softened all edges and gave it its characteristic shiny look, which was enhanced by further polishing on the wheel.
Flint Glass: An old term for glass containing lead, dating from a period when calcined or ground flint was used as the source for silica in glass manufacture, the modern term is lead crystal’.
Fluogravure: A technique devised by the Muller Family. This consists of enameling a single or two layered vessel with rich colors, partly in random patterns, then acid-etching the vitrified enameled surface into night scenes with owls and bats, bucolic scenes involving shepherdesses, flocks of sheep or packs of dogs, or various landscapes. The often iridescent effects of the opaque enameling contrast with transparent or translucently enameled portions of the vessel. Fluogravure vessels were designed in their own works at Lundville and a number were designed by Désiré and Henri Muller for Val Saint-Lambert.
Fluorspar: A common name for calcium fluoride, this is a transparent, brittle mineral which occurs in many different colors.
Foil: Very thin sheets of various metals, particularly silver and platinum. Small pieces trapped between two layers of glass form an opaque section when seen through either side, preventing light from going through it. Shredded foil suspended between the layers looks like an opaque bubble. Placed underneath a transparent glass cabochon, it lends it color. Silver foil may be tarnished before trapping between the layers to give it a different color.
Free-Formed Glass: Glass shaped entirely by the glass-blowers art and hand processes as opposed to glass blown into a mold or press-molded. Free-forming enabled the creator to produce unusual, curious, asymmetric shapes, particularly successful for Tiffany. Daum initiated the free-form Berluze shape.
Frit: The mixture of silica, potash and metallic oxides heated in a calcar or fritting furnace at a temperature low enough for the mixture to calcine but not fuse, which is then added to the cullet in a clay pot in the working furnace and which will eventually vitrify into glass. It is also called the patch.
Hydrofluoric Acid: A very powerful and corrosive acid which attacks porcelain and glass. Designs may be etched on a glass vessel by drawing the patterns on the surface, marking those areas to remain intact, then immersing the vessel in a bath of hydrofluoric acid. This attacks the exposed surfaces to a depth depending on the time the vessel is immersed. Etched areas may then be protected and other parts of the vessel exposed to the acid to complete the design. If the vessel is of two or more layers, me etching produces a cameo design. Different surface effects may be achieved with the use of hydrofluoric acid in conjunction with other agents. Thus acid mixed with ammonia gives a frosted effect, mixed with sulfuric acid it polishes crystal, and pure acid polishes the surface to a high gloss.
Intaglio: Carving, etching or engraving into the surface of the glass. The hollowed out sections are sometimes contrasted with the polished outer surface of the vessel by treating them so they are mart. In a clear glass vessel an intaglio design, seen through the solid side, appears rounded and three dimensional, the shallowest section appearing to be the thickest.
Iridescent Glass: Glass whose surface reflects different colors according to the light playing on it. This phenomenon occurs naturally in glass which has been buried for a long time, such as Middle Eastern and Roman glass. In the nineteenth century attempts to reproduce these effects were first produced by J. & L. Lobmeyr, then by Thomas Webb & Sons, but it was not until L. C. Tiffany produced his Favrile glass and J. Loetz-Witwe produced its variations on me theme that iridescent glass became truly popular. Many American and Bohemian firms produced their own iridescent glass, as did firms in Germany and France. Some iridescent glass was produced by various techniques, generally involving covering the surface of the vessel with metallic oxides either as a solid wash or in patterned design, then reducing this by heating in conjunction with carbon monoxide fumes. Metallic oxides used included gold, which produced a ruby lustre; silver, which produced a yellow lustre; and platinum, which gave silvery reflections. Copper and bismuth were also used. In addition to Tiffany and Loetz. Steuben's Aurene, Fenton, Fostoria Iris glass, Lustre Art, Quezal, Union’s Kew BIas, and Vineland Flint glass designed by Victor Durand were all iridescent glass produced in the United States, while European lustre glass was produced by such firms and individuals as Caranza, Copillet, Maximilian Boudnik, Schneckendorf, Palline-Konig, WMF, Pantin and even Gallé produced glass with some iridescence.
Lampwork: The fashioning of glassware from glass rods and tubes heated, softened and shaped with hand tools, originally in the flame of an oil lamp, later using a Bunsen burner. The technique has been used extensively in Venetian glass, as well as in notable glass designed by Karl Koepping and Friedrich Zitzmann in the Art Nouveau style.
Latticino: Clear glass vessels in which white glass threads are embedded, normally in a spiral.
Lattimo: Opaque white glass, or clear glass in which bands of white glass are embedded.
Lead Crystal: Glass containing a percentage of lead oxide. The higher the lead oxide content, the purer the metal. When cut by faceting, it scatters light with a brilliance that has led to such vessels being called bowls of fire. The European Economic Community currently imposes a minimum content of 24% lead oxide, and full lead crystal must contain 30% lead oxide.
Lehr: The annealing kiln. Built as a long steel tunnel lined with bricks, finished glass vessels are gradually reheated, then allowed to cool slowly over a period of many hours and, in some cases, several days. One end of the tunnel was hot, the other cool, and the temperature went down along it, so the annealing vessels were pulled along the lengths of the lehr. Modern Lehrs have mechanical conveyer belts, and are automatically heated, cooled and controlled.
Lime Glass: A type of glass developed by William Leighton in 1864 at the Wheeling Glass Company of Wheeling, West Virginia. It was a cheaper substitute for lead glass.
Malfin Glass: The frit and cullet are mixed in a clay hot in the working furnace, and the viscous mass needs to be stirred until fully refined, at which point it may be gathered and worked on. If allowed to mix without stirring, it eventually vitrifies as a bubbled, rough looking glass called Malfin glass. Jean Sala and his father Bienvenu deliberately chose to work with malfin glass.
Marquetry: A technique devised by Emile Galle and patented by him in April 1898. It consists of inserting cut pieces of hot, colored glass into the parison, then ensuring they were embedded in the surface by rolling on the marver. Once annealed, the vessel could be further decorated by carving. Some marquetry insets are left uncarved, and form abstract, sometimes Symbolist images.
Marver: Derived from the French word for marble, ‘marbre’, this is a marble or iron flat surface on which a parison may be rolled to smooth it. Various additives may be laced on the marver, and these are picked up by the parison, and embedded in at.
Mary Gregory Glass: A Victorian ware, basically a cheap imitation of cameo glass, an which clear or colored vases are painted with a subject, generally a boy or girl in elaborate period clothes, in white or tinted enamel, Most of it was made in Bohemia for export to Britain and the United States.
Metal: Term used to describe glass.
Mica: A group of silicates which can be cleaved perfectly to produce thin, tough, shining plates which were used before glass became generally and cheaply available. Glass is sometimes treated to imitate the look of mica.
Millefiore: Colored glass canes are grouped together, then sliced thinly and embedded in the surface of a glass vessel. The result looks like a cross between a colorful flower and a mechanical gear. The word is Italian for ‘a thousand flowers’. Frequently used in Venetian glass and paper-weights, it has also been used by Tiffany and Steuben.
Opalescent Glass: A translucent glass in which a brownish core is surrounded by bluish glass opacified by bone ash and arsenic, after which it is usually molded into a plate, vase, bowl or figurine. As the light on the vessel changes in intensity and goes from reflected to transmitted light, the object changes constantly in color from browns to blues. The thick parts are darkest, the thinnest virtually colorless, It has been produced by René Lalique, Sabino, Etling, Jobling, Verlys, etc.
Opaline Glass: Originally translucent white glass, the term was applied by the Baccarat factory to its own production. By extension it has come to mean the whole range of colored, partly translucent glass made at Baccarat. St. Louis and Choasi-Le-Roi, and later at the Boston and Sandwich Glass Co.. in the United States.
Overlay Glass: The overlay is the outer layer of a cased glass vessel. The cased vessel may then be covered in cameo carving.
Padded Glass: The addition to the parison of some glass of a different color. When annealed, this can be cameo-carved or etched, and is as effective as a two-layered vase ‘without the problems inherent in blowing one vessel into another and without the need to remove vast areas of the outer layer to fit in with the required design.
Parison: The gather of molten glass taken from the kiln on a blow-pipe and blown into its initial globular shape.
Pate d’email: A form of pâte-de-verre, an which various borates and silicates are mixed and pulverized. The paste vitrifies at a low temperature, combining with various metallic oxides which provide color. The result looks somewhat like unglazed porcelain, and is very fragile. It was made by Albert Dainmouse and François Décorcnement.
Pâte-de-Cristal: A form of pâte-de-verre ‘which has a translucent, crystalline aspect.
Pâte-de-Verre: Finely crushed glass, mixed with a binding agent (sometimes water) to make a malleable paste, and metallic oxides for color, modeled like clay, then placed into a refractory mold and heated just enough to vitrify the paste without having its constituent colored sections run together. It normally needed a very long annealing time. Pãte-de-verre may be heavy or light, opaque or translucent, matte or crystalline, depending on its components and time in the furnace. Modern Pâte-de-verre was first made by Henri Cros. It was also made by Despret, Jean Cros, Dammouse, Brateau, Décorchennont, Alméric Walter, Daum, Argy-Rousseau, Rangel d'Illzach, Frederick Carder and the Société du Chryso-cérame.
Patination: A word from the language of bronzes adopted by some glassmakers. Gallé patented a technique he called patination an April 1898. It consisted of producing a textured mart surface through extreme heating until the vessel partly devitrified, or by the action of various organic or mineral impurities. René Lalique used the word ‘patination to describe the process of applying colored washes to the surface of certain of his vases.
Paysages de Verre: Literally, glass landscapes. The term refers to vessels decorated an cameo with landscapes, seascapes, townscapes, etc. They were so named by Emile Gallé, but other glasshouses, such as Delatte, d’Argental (St. Lou’s), Val Saant-Lambert etc. later also executed such vessels
Peking Cameo Glass: Glass ware made an Peking from the late nineteenth century including a number of vases and snuff bottles decorated with cameo-cut patterns.
Plique-à-Jour: A type of transparent enameling used extensively in Art Nouveau jewelry and some other objects. It is ornate, rather like cloisonné enameling, being enclosed in shaped metal partitions, but it differs in having the enamel powders placed on a disposable surface which disappears, or is removed once the powders have vitrified. Plique-a-jour enamel is at its best when light streams through it.
Pontil: An iron rod, also called a punty, to which is attached the partially shaped parison. A small blob of the gather is picked up by the tip of the pontil and the parison attached to this at the opposite end to that which is attached to the blow pipe which is then detached. Shaping continues by the use of various hand tools; handles, appliqués, etc. are put on, and the vessel readied for annealing. Removing of the pontil leaves a rough shear mark in the center of the base. Some firms, such as Tiffany, frequently leave the pontil mark in its rough state. Others, like Loetz, invariably polish them to a concave disc shape. The pontil mark was eliminated by some firms by either blowing the base into a mold, or by using a variation of the pontil such as a gadget which had pincers to grip the base rather than be attached to the center.
Potassium Carbonate: also known as potash, this is an alternative alkaline ingredient for making glass replacing soda.
Press-Molded Glass: This is glass made by pouring melted glass into a metal mold, then pressing it in by the use of a lid. The outer surface of the resultant glass object is the exact shape of the interior of the press-mold, and is generally solid throughout, unlike a mold-blown vessel, which is blown into a mold, and thus has a hollow interior. Press-molding is particularly suitable for figurines and DO~Vls, light fittings, etc. which have relief decoration on them. Blow-molding is particularly suitable for vases or other hollow items.
Prunt: A small blob of glass which sticks out of the main .body of the vessel. It may be applied to the surface, or shaped by pulling it from the surface while still malleable. Punts are often used for decorative purposes, and may be of various sizes and shapes, round or pointed and may be positioned randomly or in precise patterns. They are sometimes useful in affording a firm grip on a vessel without handles.
Punty: Another name for pontil.
Pyrogravure: Sometimes known as poker-work, this consists of making designs in wood, leather and other such materials by fire, which chars the pattern.
Refractory Mold: A mold made of a material that does not crack, break or change shape in the extremely high temperature of the kiln. These molds have been made of fireclay, carved stone, and metal for various purposes, and may be made in one part (which means they must be broken to extract the contents) or in, two hinged parts which makes them re-usable. More complex shapes may involve molds made an three, four, or more parts. Molten glass is poured into the molds, and the molds are then subjected to heat sufficient to vitrify the molten glass.
Reticulated Glass: Glass which has been blown into a metal armature which has apertures through which the glass may bulge out. Tiffany used the technique, while Daum executed a number of vases and bowls blown into wrought armatures by Majorelle, a design that was copied by several other firms, including dAvesn and Muller, with the metal part made by a variety of firms, including that of Edgar Brandt.
Sandblasting: A method of decorating glass by masking parts of the surface, then attacking the exposed parts with jets of grains of sand at high velocity. Special machines can vary the intensity, and different sizes of sand may be used. Sandblasting can produce shallow cutting as well as very deep cutting into the surface, and the hollowed out sections may be polished, or rendered matte with acid or acid fumes.
Satin Glass: Glass which has been given a frosted, satin finish by the use of hydrofluoric acid or acid fumes.
Silica: A hard, crystalline substance which is an essential ingredient in the manufacture of glass. It occurs in nature in such mineral forms as sand, flint, quartz, etc.
Soda Glass: Glass made with soda, rather than potash, as alkali. It is fairly light in weight and easy to handle. Much Venetian glass is made with soda.
Template: A pattern, made of wood or metal, which can be used to transfer serial designs onto glass blanks.
Tessera: (Plural Tesserae) A small segment of glass, ceramic, marble, earthenware, etc. which is joined by others to produce a mosaic.
Threading: The process of applying glass threads to the parison. When the glass threads are not embedded in the body of the vessel, they are said to be trailed over the surface.
Turtle Back: A type of glass tile manufactured by L.C. Tiffany in translucent iridescent glass. Made in various colors and sizes, these tiles were often used in decorative friezes in both shades and bases in some leaded-light lamps.
Uranium-Oxide: A metallic oxide used in the manufacture of glass to produce yellow and greenish colors.
Verre Double: (Triple etc.). The terms used by Gallé to indicate cased glass, that is glass having two (or more) layers which could then be carved or etched in cameo.
Verre Eglomise: The process by which a design in silver, gold or enameling was trapped between two layers of glass. The term has been used loosely and inaccurately to describe certain types of pâte-de-verre.
Vetro di Trina: A term loosely used to refer to glass with filigree decoration.
Vitrification: The process by which certain substances, basically silica and an alkali, fuse together at the appropriate temperature to become glass.
Wheel-Carving: The process of decorating the surface of the glass vessel by grinding on a lathe, or wheel, with a variety of metal discs of various sizes. The vessel is held up to the underside of the rotating wheel in conjunction with an abrasive. Great skill is needed. Wheels of cork, wood and leather are substituted to polish the vessel.
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