This is a coloured opaque glass whose preparation is based on the same principle as the lattimo glass. In this case, however, white microcrystals are dispersed in a colored vitreous phase. Others, differently, are obtained with coloured micro-crystals dispersed in either a colorless or a colored vitreous phase. In the first case lattimo is used (microcrystals of calcium and sodium fluoride) or white enamel (amore intense white completely opaque even in a thin layer, generally obtained with micro-crystals of arsenic and lead) dispersed in a transparent coloured glass. The white microcrystals, in addition to making the glass opaque, soften the colour of the glass in which they are inserted, that must contain a high percentage of colouring agents. In the second case “cores” are used: these are semi-finished crystalline structures based on lead antimonate or stannate that are yellow or red. These are added to the molten mass just before processing because they are compounds that dissolve easily.
Pezzato (lavorazione a tessere)
This glass is like a patchwork with elements of different colours and is obtained as follows: on a metal plate a series of segments of flat rods, according to a given design are arranged. The plate is heated to take the segments back up to the melting point: at this stage the set of molten fragments is made adhere by rotation to the outer surface of the vase still on the tip of the blower’s pipe. After the pieces have been joined together, they are finished by appropriate smoothing over and modelling.
Glass with a spongy appearance, with a great many air bubbles, to the point that it is almost opaque. The homogeneous and refined molten mass (with no air bubbles or impurities) is vigorously mixed in with salts (generally sodium carbonate or bicarbonate) that decompose due to the heat and liberate gases (carbon dioxide) dispersed in the form of bubbles of varying diameters.
This is a variant of the “filigrana” already known in Murano in the XVI. It is obtained by joining two conical vases under heat, covered externally with thin coloured rods, one arranged clockwise and the other anticlockwise. A network is thus formed with a rhomboid-like mesh. The rods with different thickness, within each quadrangle, cause the characteristic air bubble.
This is a process to get the same results as the “acid” process without, however, the latter’s negative aspects, linked with the use of toxic substances. Sand or alumina powder is sprayed onto the glassware with a compressed air device. The impact of the granules on the surface causes microfractures that make it opaque. Sanding is marked to a greater or lesser extent by an appropriate adjustment of both air pressure and granule size. Used mostly on flat panes, this technique has also found application in the preparation of some drawings by masking some of its parts.
This is a glass that imitates the effect caused by long periods spent underground, typical of glass objects found during archaeological diggings. During manufacture, a mixture of several powders is dispersed on the surface of the object at a temperature of about 800 C. These adhere irreversibly and give the special effect of opaqueness and colouring. To improve adhesion the piece is heated again. The powder mixture contains melting components (carbonates or nitrates that decompose under heat and act as binders; inert opaqueness (talcum, silica, etc.) other colouring agents. This technique was introduced in the early 50s.
This is a glass invented in the early 50s. The procedure for its preparation was as follows: a large concentric-ring murrina was made with two alternating colours; it was then heated again and applied while hot to the item being processed. After a first finishing step, and after cooling, the item still with an irregular shape was modelled and polished at the grinding wheel with an extremely long and delicate operation. With this complex and laborious technique, a limited number of items was made, very rare and refined, that for their essential shape and decor represent the very best Muranese production, with a level of quality that compares well with that of northern Europe.
Enamels wide spread in Murano since ancient time. While up to the mid-nineteenth century every craftsman made his own on the basis of very particular and jealously kept recipes, it later became fashionable to adopt vitreous enamels produced on an industrial scale. They must have the following features: applied cold to the item during manufacture, they must fuse at a temperature lower than that of the glass, their colours should not fade at high temperatures and they should Ave a coefficient of expansion as close as possible to that of glass to prevent breakages during the cooling stage. Once the decoration is finished, the item is placed in a small “muffola” oven where it reaches a temperature of some 550/600 C to allow the enamel to fuse without deforming the item. In the Novecento this technique was used to make copies of ancient models, but a few exceptions.
This is a glass coated with a thick layer of colourless transparent glass, or with a glass which has a colour different from the one of the backing. It consists of a layer of coloured glass with the inclusion of air bubbles and gold leaf, more rarely with the subsequent application of rods in pulegoso glass, coated with a colourless transparent layer about one inch thick. Many Muranese glass factories extensively took up this technique with very considerable results.
A glass invented during the late 30s it is based on the traditional filigrana, technique with particularly thin rods used in this case, joined one to the other with especially refined alternating colours. On occasion to enhance the surface even further, it was lightly “battuto” at the grinding wheel.
This is a glass rod executed with the same procedure as the “murrine”. A sheaf of rods of different colours is prepared with a given design, it is heated to the melting point; two metal rods are then attached at the ends of the molten mass while two maestros draw it out and impart a movement of rotation. The fluidity of the material is such that it can be twisted at will to assume its characteristic spiral-like shape inside. This type of object was already known in Murano in the XVI century with the name of “a retortoli ” glass. The current name of “zanfirico” is taken from the Venetian nineteenth century dealer Antonio Sanquirico who proposed this process anew.