Museo del Vetro

Glass Museum



AVOLIO A spool-shaped element, usually in clear cristallo glass, used in a goblet or vase to join the bowl to the stem, or the stem to the foot.

BALLOTON Technique used to obtain a particular optical effect. It is based on the use of a metal die, with the inner walls containing small square based pyramidal “spikes” which, when the glass is blown, result in a cross-relief pattern. By casing a gather (péa) stamped in this way in a layer (coperta) of glass, an effect is obtained whereby hundreds of minute air bubbles are trapped between two layers of glass. When gold leaf is added to the péa after it has been blown into the ballotton mould and is then removed with a brush from the areas covering the indentations, another interesting effect of gold lattice or honeycomb pattern is obtained.

BIANCO LATTE Opaque fluoride glass used mainly in jacketed glass for lighting fixtures.

BOCCA Mouth of the furnace or also glory-hole, the hole in the side of a glass furnace from which the molten glass is gathered or heated during the successive working stages. Also bocca del paelato, bocca della fornasa. During melting, the mouth of the furnace is closed with a lid, or cover.

BOLO Gather. A Murano word referring to the molten glass gob collected from the crucible on the end of the blowpipe or gathering iron.

BORSELLA Pucellas, crimps, or jacks. Flexible iron tongs used to shape the molten glass. It can have different forms and uses: da siegar. to squeeze or open the pèa; da pissegar; rigadin, crimps which give an embossing effect like the ribbing on leaves, the shape of flower petals etc. Together with the blowpipe, borselle are the glass master’s main and most versatile tool.

CALCHERA Lime kiln. Reverberatory furnace constructed so that the vault reflects the heat of the flames onto the floor; used for making frit by calcinating the batch at 700-800° C.

CANNA DA LEVAR Blowpipe, the basic tool in glassmaking. Probably invented by Syrian glassmakers in the second half of the 1st century BC. It is a hollow metal tube, usually 1.4m long, onto which the molten glass is gathered from the melting pot; the end opposite the mouthpiece is thicker and is preheated to help retain the gather. This end of the blowpipe is plunged into the melt and repeatedly rotated. With this manipulation, the molten glass, which is sufficiently viscous, collects around the end in a gob, usually called a gather; the gather is first marvered. i.e., rolled on the marver, a flat plate either in marble or bronze, today in cast iron, and is then slowly blown into a hollow sphere. This is the first in a number of operations that will result in the finished glass object. In Murano parlance, the word canna appeared only in the 19th century, while from the 14th century onward the blowpipe had been called ferro o ferro sbuso (iron or hollow iron).

CANNA DA PERLERI Bead-makers’cane. Clear or opaque glass rod, obtained by manually drawing a large gather; drawing is done in a long corridor next to the furnace room, after attaching a pontil to the other end of the gather, by pulling the soft glass from both ends until the cane has reached the desired length and thickness.

CANNA DA SPEO Literally, spit or skewer cane. Hollow cane with a fairly large bore cut in segments that are then skewered on thin metal rods to be fire-rounded. These larger beads were used to make paternosters (prayer beads similar to rosaries) or necklaces.

CANNA MASSICCIA Solid cane, rod.

CANNA ROSETTA Rosetta canes are solid or hollow canes made of several layers of glass in different colours. Once each layer is gathered, the cane is moulded in an open die with a star cross-section. After layering, the cane is cut into small cylinders whose cross-section shows the characteristic pattern of concentric stars. The sections are used to make beads, necklaces, blown objects and solid glassware. By incorporating slices of solid rosetta canes to a gather and reheating, the small discs become embedded in the glass and can be blown to obtain the millefiori effect. In Murano, the production of rosetta canes dates back to the 15th century.

CANNA SBUSA Hollow rod with thicker or thinner walls, tube, pipe.

CANNA STAMPADA Rod or cane with a polygonal outer section instead of the more usual round cross-section.

CAVADA O CAVADA DE FOGO Summer period of inactivity of the furnaces during which the fires were put out, the kilns were idle and the whole production was stopped.

COLATURA A technique used in the manufacture of plate glass for windows and mirrors. Invented in France in the late 17th century to replace earlier methods of producing broad sheet glass, this process involves pouring the molten glass into shallow rectangular moulds.

COLLETTO The small band of glass which remains attached to the tip of the blowpipe or punty after the object fashioned has been cut off; the term first appeared in Murano documents in 1496. The English cullet is a derivative, and is synonymous with scrap glass suitable for re-melting.

CONCA Large shallow cast iron vessel with a concave base containing molten glass that has been removed from the melting pot and that can be later reused as scrap glass in another batch.

CONTERIE This term indicated the glass beads made by cutting a hollow cane and giving a round shape to the cylinders thus obtained. Larger and thicker beads were fired on metal spei (skewers); this work was done by the paternostreri (rosary bead makers). The same term also indicated the thinner seed beads or bugles made by the suppialume who fashioned the beads by lampworking a solid glass rod. Starting from the nineteenth century the term defines the very small monochrome seed beads that were once called margarite, in which case the rounding of the cylinders was done by heating the beads in special copper trays called ferrazze and subsequently finished by hot-tumbling them in a rotating drum.

CONZAOR Glass worker who prepared the mixture for the melting of the batch. The “conzator vitreorum” appears in a document dated 1444. The conzaori directly supervised the Friulian workers who helped them in these tasks.

CORROSO Literally, “corroded”. A rough, stone-like finish achieved by exposing the glass to fluoridic acid. The surface of the glass object is covered with an irregular layer of melted wax applied with a sponge; the object is then immersed in a vat containing sawdust and hydrofluoric acid to obtain the corrosion of the areas unprotected by the wax. The result is similar to a frosted surface. The method has now been abandoned due to the health risk related to the use of hydrofluoric acid or its salts.

COTISSO Literally, half cooked. Glass that was not cooked or fined thoroughly. In the past the term indicated first-melt glass that was taken from the melting pot and dunked in water to break it up into pieces and was then re-utilized in another batch as a catalyst. Today, cotizzo is synonymous with scrap glass, the shapeless glass mass left in the melting pot at the end of the working process, which is transferred to the conche to be used as scrap glass in the next batch.

COVERCIO The cover over the mouth of the furnace while in operation; it has a small hole in the middle where to insert the tip of a metal tool used as a handle used to shift or remove it. The smaller doors are called portine.

CROGIOLO Crucible. Container or melting pot in which formerly the frit, now the mixture of the various raw materials, mixed with cullet, is melted to form glass. Melting pots were usually made from a mixture of silica and refractory clay, and their manufacturing process required many months of slow drying after forming. Melting pots come in various shapes and sizes, and in the past could contain only several tens of kilograms of molten glass. Today, modern crucibles can hold up to a ton of melt. Shapes were generally cylindrical, with a round or oval cross-section. For some types of glass, leaded glass, for example, the so-called covered melting pots may be used; this solution reduces loss due to lead volatilization.

DIATRETA Cage cup or reticulated cup. Winckelmann gave this name to particular 1st-4th century BC glass cups or beakers showing intricate openwork. This technique consisted in blowing a vessel of notable thickness, followed by the careful cutting of the exterior to remove the superfluous parts, so that the vessel appears to be enclosed in an openwork cage attached to the body only by thin stems or shanks. Classical examples of this process are the Trivulzio Cup and the Constable Maxwell Cup.

FAçON de venise “In the Venetian style”. Finely-blown soda glassware, often with produced in the 16th and 17th centuries by Murano glassmakers emigrated to the Netherlands and Spain.

FANGO DI BARENA Saltmarsh mud, clay from the bottom of the lagoon marshes used as a non-stick material for hot glass.

FARASSA Square metal tray on which the glassware is placed in the annealing furnace.

FLINT GLASS Term used to indicate English lead glass obtained after long experimentation, by adding lead oxide to the batch. The formula was patented by George Ravenscroft in 1674.

FOGLIA D’ORO E D’ARGENTO Leaves, or thin sheets of gold or silver, used for the production of gold or silver mosaic glass. Leaves are generally 8x8cm in size and so thin that 20 grams of gold will yield 6 cubic meters of foil. In glass blowing, the parison may be rolled in leaf, picking it up and then casing it by dipping it again into the melt. Further blowing tears the leaf apart into small fragments or gold or silver dust in an organized way, giving a decorative effect. The earliest recorded examples Venetian gold leaf glass date back to the second half of the fifteenth century.

FONDITA Fusion, melting. The process of transforming the batch (the raw materials) from its solid crystalline state into a fluid, amorphous, vitreous melt. The operation includes the initial phase of placing the batch (in the past, the frit) into the furnace, the actual melting, and the fining to obtain a homogeneous melt free of air bubbles. In the past, the furnace could reach a temperature ranging from 1000° to 1200° C, so that melting might take 4 to 5 days before workable (i.e.homogeneous, fined) glass was obtained. The melt was obtained in a two-stage process: first the vitrifying agent and the flux were mixed at a low temperature in order to start chemical reactions, and then the frit was fused in the melting pot. Lead crystal involved a third phase: after the first fusion, the melt was poured into water to homogenize it and dissolve the unwanted insoluble salts, and then it was finally melted one more time.

FORCELLA Fork, a long metal rod with a forked end, used by the forcellante to load, move, or remove glassware into/from the annealing furnace.

FORFE Scissors used by the impiraressa (bead stringer), but also, when in a particular shape, tagiante or glass cutting shears used by the glass master.

FRITTA Frits are intermediates in the production of raw glass, used in the past and until the beginning of the eighteenth century (with the introduction of potassium nitrate) to speed final fusion. The vitrifying agent and the flux were mixed together, sometimes with some water added to the mixture, and the batch was placed in the calchera (the lime kiln), a low-temperature (700-750 ° C), reverberatory furnace for several hours. The first chemical reactions begin in this kiln, not always resulting in a melt, but with the formation of alkaline silicates, which melt more readily, and the elimination of the carbon dioxide formed by the decomposition of carbonates, and any carbonic residue in the plant ash used, which, in turn, makes fining the subsequent melt much easier. After these operations, even if not immediately, the frit, with the possible addition of colouring agents, opacifiers and cullet, was melted in the melting pots; fusion occurred in two stages, frit formation and the actual fusion. This process accelerated melting time, which, given the low temperatures of the furnaces – around 1000-1200 ° – were however significantly long, even 4-5 days in the sixteenth century. Today, the melting temperatures in crucible furnaces reach up to 1400 ° C and frit is no longer a necessary intermediate. The term frit appeared for the first time in a Murano document dated 1347, while an earlier name for this intermediate product was “maxi vitrei” as reported in the 1271 capitulary of the fioleri (glassmakers’) guild.

GASTALDO Between the 13th and 18th centuries, the leader of the glassmakers’ guild, who acted as representative of the glassworks’ owners, by whom he was elected each year.

GIOSSA, GOCCIA, BATAVICA Batavia’s tears, Dutch tears, or, more commonly, Prince Rupert’s Drops, are small objects with a characteristic tadpole shape that are obtained by dropping a small quantity of molten glass into very cold water. Their name derives from the old name of Holland, Batavia, from where these objects were first introduced into France in 1656 by a Swedish ambassador.

GIRASOLE Girasol glass, a type of opalescent glass opacified with lead arsenate, resembling the iridescent fire opal by the same name. This glass process was introduced into Murano technology in 1693, and was produced following a chemical composition formulated by G. Darduin.

INGHISTERA, INGHISTARA, ANGHISTERA Archaic name of a long-necked, handless jug. Like the moioli or muioli (the ordinary drinking glasses), it was a mass-produced object of little aesthetic value, manufactured in Murano by “second class” glassmakers called buffadori.

LATTIMO The name given in the past to the opaque, white “milk” glass, similar in appearance to porcelain, made in Murano. Also called laterolo or porcellano. The opacifying substance used is tin dioxide, which is added to the glass composition as tin lime and/or lead and tin lime.

MILLEFIORI As early as the second half of the fifteenth century, Murano glassworks developed the technique of decorating the wall of blown glassware with thin slices of complex rosetta canes characterized by concentric layers of different colours, sometimes forming the typical star or flower patterns. The name millefiori given to this decoration derives from the fact that the surface of the finished vessel is reminiscent of a field of flowers. This technique was never totally abandoned and enjoyed great popularity in the late nineteenth century and Art Nouveau period.

MOLADURA Wheel grinding, etching, engraving. Finishing phase of the production of a glass object, in which the piece is ground, sanded and then polished, using a series of finer and finer grinding wheels and disks of different abrasive capacity.

MUFFOLA Muffle furnace, a low-temperature box-type kiln for refiring glass, also called a fermo (stationary), to distinguish it from the tunnel kiln in which the glassware is placed in carts moving along a tunnel, while muffle furnaces only have shelves. Furthermore, while tunnel kilns are continuous furnaces, the muffle furnace is discontinuous in the sense that the annealing cycle begins only when the muffle chamber is filled with objects to be fired.

MURRINA Term used to indicate glassware made with a method that dates back to ancient Roman and Alexandrian times. The technique was revived in Murano in the 1870’s, and involves arranging short lengths or slices of cold canes, sometimes even prefabricated elements, on a metal plate according to a predefined design, forming a polychrome mosaic which is then placed on refractory material. The composition is then gradually heated up at the mouth of the furnace to soften the mosaic elements; with the help of appropriate paddles and tools, the whole is compacted to join the various elements and form a single object. This flat disc, while still hot, is then slumped over a convex shape in refractory material and then picked up to embed it in the surface of an item having a cylindrical shape, still connected to the blower’s pipe. After annealing, this glassware must be rectified, ground and polished to remove thickness irregularities and make the surface smooth and glossy.

OPALA, OPALE, OPALIN, OPALINA Glass that resembles an opal, being translucent and white, with a grayish or bluish tinge so that it is also called acqua (aqua, water) or anice (anis). Opacified with lead arsenic, this type of glass first appeared in the seventeenth century and is also called girasol.

PEA, PELA from pera, pear; parison, the first stage in the making of any hollow glass object. In this stage of the glassmaking process, the parison is first marvered (marmorizzada), then reheated, more air is blown into the bubble, which is then rounded (magiossada), until it becomes a hollow glass piece ready to be handed over to the glass master for finishing.

PINSE Tweezers are used to pull, squeeze and shape hot glass.

PIRIA Funnel. In the manufacture of glass beads it indicates a funnel-shaped iron vessel, in which sea sand and mixture of lime and charcoal were added to fill the holes of beads before they were rounded in the furnace

PONTELLO Pontil or punty, a solid iron rod that is tipped with a small amount of hot glass onto which a blown article is transferred from the blowpipe for final shaping and finishing. Also, solid iron rods, approximately 10 cm. long and from 10 to 30 mm. in diameter, used by the glass master’s assistant to remove the glass from the furnace. The thinnest pontil is called speo (spit or skewer).

PULEGOSO Bubbled glass produced by adding to the melt a substance that will create gassy bubbles. Pulegoso was developed by Napoleone Martinuzzi, and was a very popular technique in the 1920s.

RIGADIN AND RIGADIN RITORTO Thin ribbing obtained by blowing a glass object inside an open die, generally in bronze, which has grooves with a triangular cross-section. The piece thus becomes ribbed and can also be twisted inside the mould to produce rigadin ritorto(swirl or twisted ribbing). After heating at the mouth of the furnace, the twisted piece can be placed in the mould one more time and twisted in the opposite direction to obtain criss-cross ribbing.

SATINATO Glass treated with hydrofluoric acid and ammonium fluoride, which gives the glass surface a silky, satin finish.

SCAGNO Stool or bench. Backless wooden bench which is the glass master’s workstation. It has a very wide seat with two extended armrests, called bardelle, on which the master rolls the blowpipe or pontil holding the glass that is being fashioned; it is wide because it must contain all the hand tools he uses.

SESSOLA Wooden vessel with a concave bottom, where the impiraresse, the bead stringers, kept the beads they were stringing onto the needles.

SOFFIATURA Glassblowing was invented in the second half of the first century BC probably in the Syro-Palestinian area and soon exploited by the flourishing Roman glassmaking industry. Glass blowing was the most revolutionary discovery in the evolution of glassmaking techniques; eventually, it led to the abandonment of most other traditional glass working methods, such as casting and core-forming, until then the only techniques in use, and soon glass became highly competitive in the production of many objects for everyday use previously manufactured in clay or pottery. Glassblowing can be further divided into free blowing or mould blowing.

TAGIANTE Shears used by the glassmaker during the shaping stage of the piece to cut away excess glass. They are divided into tagianti dritte (straight shears) and tagianti tonde (diamond shears). The former have straight-edge blades like regular scissors and are used for linear cuts, while diamond shears have angled blades with the sharp edge on the inside used to make round cuts.

TAGIOL Rectangular metal paddle with a wooden handle and sharp edges, used by the glass master to make small indentations or rows on the surface of the parison.

TAMISO Wooden sieve with a very fine wire or steel mesh used by the omo dele partie (the glassmaker who was in charge of the chemical composition of each batch) to sift the sand and remove larger grains or other impurities.

VESSIGA Literally, bladder. Muff, large cylinder-shaped glass blown into an elongated balloon in the initial stage of the production of plate glass for mirrors.