Murano Glass Dictionary
The term “ avventurina” describes a glass invented in Murano around 1620 which is formed from tiny crystal of copper wrapped in a glass mass. The secret of “ avventurina” working, held in the centuries by a few glassmakers, is to add a completed fusion specific quantity of raw material such as iron typing, silicon metal and coal, up to the precipitation of copper. The homogeneity of distribution of crystal’s copper characterize “avventurina”’s quality.
The origin of the term “avventurina” takes its name from a definition given, in the seventeenth century, by glassmaker John Darduin: "la si dimanda venturina, et con ragione, perché sortisse più per ventura che per scientia".
It is called crystal the colourless and transparent glass, decolourized with manganese dioxide, obtained with purified raw materials. Since the Middle Ages the crystal is considered the finest Murano glass. The secret of its quality lies in the purify of raw materials used, use of bleaching, preparation of mixture and conduct of fusion. In the mid-fifteenth century, Murano proposed a pure and colourless glass, that for the fist time in history it was called “crystal” and was subsequently reproduced in other european countries. The sodium crystal is very suitable for the production of very light blown-glass objects that require long working times.
It is a glass obtained with a hot decorative technique, which involves use of chopsticks containing smooth wires in “ lattimo” or coloured glass.
“Lattimo” is a matt white glass such as milk, the invention is dated in 1450 in Murano in order to imitate chinese porcelain arrived in Venice. Higher is the concentration of zinc oxide in the mixture, higher will result homogeneity of crystals.
Similar to “ lattimo”, from an aesthetic point of view, is “ vetro smaltato” with lead arsenate especially used in the working of pearls and “ filigree”.
In the middle of fist century b.c. was a technique that revolutionized glass production, making rapid and accessible the production of glass bowl helping the spread even at most modest classes. The origin of “ soffiatura” occurred in syrian-palestinian area. At the beginning there was not a real blowpipe but a hollow pipe that it was closed at one end allowing the modelling in that zone in the form of small bottle, while in the other end was done the blowing generated by master glassmaker.
In a second time the modelled object was removed from the rest of glass pipe.
The introduction of a metal pipe made easier the work of glassmaker and increased the range of procuts.
The “ sommerso” is a type of glass art of Murano which presents layers with contrasting colours. The technique consists in immersion of “ soffiato” with a large thickness into melting pot containing transparent glass or other colours with the same thickness. The overlap of thick layers of transparent glass allows to obtain special chromatic effects. This process is a popular technique for vases and it is sometimes used for the sculptures.
The “ conterie” are glass beads rounded off or sharp edge obtained with “lume” processing, cutting perforated tubes placed in the furnace for about ten meters. The glass pipe undrilled is softened by the heat of fire (from a torch), subsequently wrapped around a metallic tube which gives the pearl the wanted shape and finally decorated using of polychromatic glass.
Decorato a smalto
The technique of glass decorated with enamel involves the use of coloured compounds obtained with dust of low-melting opaque and transparent glass finely mixed applied by a brush on the surface of the glass to realized a decoration which can takes abstract shapes, vegetable or figurative. The decorated object is subsequently subjected to a thermal cycle that does not exceed 500 °C, in this way glass applied with a brush adheres permanently to the glass surface used as support.
With “ Millefiori” is called a perforated or undrilled pipe that has within it several concentric glass layers of different colours and shapes (usually flowers or stars). The processing involves the use of open molds that impress step by step different shapes depending of different colour layer and subsequently the position of the pipe for ten metres. A special type of “ Millefiori” pipe is “rosetta” which is dated in the fifteenth century characterized by star pattern in white, red and blue glass ( with alternative layers). The “ Millefiori” pipe is usually cut into sections called “ murrine”.
The parts obtained from a perforated pipe ( after being grinded) can became pearls.
While non-perforated sections may be side by side and fused by heat of the oven so can be packed plates and bowls and if fused to the bottom of a small hemispherical mass of crystal, pressa carte or presse-papier.