Murano Glass

The Venetian art of glass comes directly from the Roman one of the Upper Adriatic and, in any case, the real development took place in the Middle Ages, where art and craftsmanship were further enhanced. The Venetian glassmakers began to practice this art by inheriting the use of sodium glass from the Orientals. This composition is suitable for hot processing and in this they skillfully distinguished themselves for their aesthetic taste and the use of multiple colors. The aesthetic ability for Venetians is based on the intuition that glass is an extremely malleable material and therefore suitable for being blown and modeled in an incandescent state, but capable of maintaining the same chromatic characteristics even in the finished product. This differs from the Nordic tradition, which holds that glass is the equivalent of hard stone and therefore that the skill lies in enhancing objects through cutting. The first documents that reach us on the Venetian glass art date back to the year 982 AD, the year in which the name of a glass craftsman appears in Venice, so we can assume that this art, still active, is more than millennial all over the world . After 982 there was confirmation of the existence of other Venetian glassmakers, but in the thirteenth century the predominance was clearly of the Murano artisans. This was due to the fact that the glassworks naturally concentrated on the island of Murano, so much so that in 1291 the State established the destruction of glassworks built in Venice, assigning their historical origin to Murano, so much so that today some dynasties glassmakers have produced their business continuously.

It is believed that the glassworks originated in Murano in the 8th century, with significant Asian and Arab influences, since Venice was an important trading port. The fame of Murano as a glass processing center was born when the Republic of Venice, to prevent the fire of the buildings of the city (at the time mostly built of wood), ordered the glassmakers to move their foundries to Murano in 1291 and the first arose in the well-known rio dei Vetrai. Contrary to other countries where glassworks were located in the production sites of raw materials or fuel, Venice and Murano have always imported all materials such as vitrifying silicon, melting soda and more, from distant places, including wood, fuel up to to the last century, which came from the Istrian and Dalmatian coasts. The true quality of the island of Murano, however, was the man with his experience, who over time has perfected the styles, the quality and the ability to shape the incandescent glass. These glass artists have always been contacted since the Renaissance to bring their skills to the courts and workshops, so much so that they became masters. In fact, for this reason, a glass school was activated in Murano that initiated young people to this profession even if the experience in the glass factory remained unique. In the Middle Ages and the Renaissance, Murano glass was required by the highest social classes in Europe starting with the invention of crystal in about 1450; in fact the crystal is a quality of glass that differs and that gives the glass itself some peculiar characteristics due to the same silicon base but to a higher percentage of lead oxide (24%), so the products created were particularly refined to satisfy the demand for extremely wealthy clients. In the Baroque period the research was transformed through the execution of effect objects such as lattimi, that is compositions based on silicates, tin and lead with a milky white appearance, hence the etymology, which perfectly matched the furniture of the Venetian eighteenth century also in the decadent era of the Republic of Venice. After the end of the Republic of San Marco in 1797, the rebirth of glass craftsmanship took place in the second half of the nineteenth century and the glassworks that were born developed techniques still in use today and which gave rise to contemporary and design glassware.

The category of Murano glassmakers soon became the most prominent on the island: in fact, from the fourteenth century glassmakers were allowed to carry swords, they enjoyed immunity from legal proceedings by the Venetian state and their daughters were allowed to marry with the wealthiest families of Venice. However, the glassmakers were never allowed to leave the Republic. Many artisans took the risk of setting up processing ovens in surrounding towns or in distant countries such as England and the Netherlands. At the end of the 16th century, three thousand of the seven thousand inhabitants of the island of Murano were involved in some way in the glass sector. For several centuries, the glassmakers of Murano maintained a monopoly on the quality of glass, on the development or improvement of techniques, including those of crystalline glass, enameled glass, glass with gold threads (avventurina), multicolored glass (millefiori ), glass-milk (lattimo) and precious stones imitated in glass. Today, Murano artisans are still using these centuries-old techniques in every process: from contemporary glass art to Murano glass figurines, to chandeliers and wine corks. Today, Murano is home to a large number of factories and studios-workshops of individual artists who create all sorts of glass objects for both mass marketing and original sculptures.

What is the Glass

Glass is made up of silica, which becomes liquid at high temperatures. Before the glass goes from a liquid to a solid state, there is an interval where the glass becomes soft and malleable before it hardens completely, allowing the craftsman to shape the material. In addition to silica, other raw materials, called flux or fluxes, soften at lower temperatures. The more sodium oxide in the glass, the slower it solidifies. This is an important factor for manual glass processing, as it allows the glazier more time to shape the material. The various raw materials that a craftsman can add to a glass mixture are sodium, to make the glass surface opaque, nitrate and arsenic, to eliminate bubbles, and dyes or opacifiers. Colors, techniques and materials vary depending on the result the glassmaker is trying to achieve. Murano glass processing can be divided into two categories: first processing and second processing. Those processes that use the raw material, that is sand, soda and other compounds, or the raw glass, called cotisso, fall into the first processing. These elements are melted in specialized ovens in order to obtain the vitreous mixture which is subsequently processed. On the other hand, the second process includes lampwork with the use of glass rods, glass fusing and "cold" processes such as decoration, engraving and grinding.

"Hot" processing

In "Hot" processing, all glass processing methods that require the melting of the raw material or waste from previous processing are included:

Aventurine

The term "aventurine" describes a glass invented in Murano around 1620 which, at first glance, has innumerable golden specks wrapped in the mass, in reality they are very minute copper crystals. The secret of the composition of aventurine, held over the centuries by a few glass masters, lies in adding, once the fusion is complete, appropriate quantities of raw materials such as beating iron, metallic silicon, coal, until the metallic copper begins to precipitate. A slow cooling cycle of the molten glass causes the metallic copper to separate from the base glass. The homogeneity of the distribution of copper crystals characterizes the quality of aventurine. The origin of the term aventurina takes its name from the definition given by the seventeenth-century glassmaker Giovanni Darduin: "venturina is asked, and with reason, because it came out more by chance than by scientia".

Crystal

"Crystal" is defined as colorless and transparent glass, decoloured with manganese dioxide, obtained with purified raw materials. Since the times of the Middle Ages, crystal has been considered the most valuable Murano glass. The secret of its quality lies in the purity of the raw materials used, in the use of bleaches, in the preparation of the vitrifiable mixture and in the conduct of the melting. In the mid-fifteenth century the Murano people proposed a pure and colorless glass, which for the first time in history was called crystal and was subsequently reproduced in other European countries. Unlike the Nordic crystal, which has a high concentration of lead oxide and which today must undergo strict controls relating to the fumes deriving from the fusion, the Murano crystal is a sodium-calcium glass whose main components, in addition to silica, are the sodium oxide and calcium oxide. Sodium crystal is very suitable for the production of particularly light blown objects that require long processing times.

Watermark

It is a glass obtained with a hot decorative technique, invented in Murano in the first half of the 16th century. It involves the use of rods containing smooth threads in "lattimo" or colored glass. If the threads in the rods are twisted, or spiral, the watermark is called "retortoli" while if the rods are crossed the watermark is defined "reticello" or "double".

Lattimo

Lattimo is an opaque white glass like milk (hence the name), the invention is dated around 1450 in Murano with the aim of imitating the Chinese porcelain that arrived in Venice, using lead and tin mortar as opacifying agents. In the Renaissance and in the eighteenth century, lattimo was used above all for the production of refined blown objects, decorated with polychrome enamels. In today's processing, the opacifying agents used are characterized by minute crystals of calcium and sodium fluoride which separate from the molten glass during cooling. These crystals are all the more homogeneous the higher the concentration of zinc oxide in the mixture. Similar to lattimo, from an aesthetic point of view, is lead arsenate-based enamel glass, used above all in the processing of pearls and filigree.

Blowing

The blowing around the middle of the 1st century BC it was a technique that revolutionized glass production, making the production of glass containers quick and accessible, favoring their diffusion even among the most modest classes. The origin of the blowing occurred in the Syrian-Palestinian area, initially there was no real blow pipe but a hollow glass cane that was closed at one end allowing modeling in that area in the form of a bottle, while at the other end the blowing generated by the master glassmaker took place. Later the modeled object was detached from the rest of the glass barrel. The introduction of a metal barrel made the work of the glassmaker easier and expanded the production range.

Submerged

The "submerged" is a form of art of Murano glass that has layers of contrasting colors (usually two), the technique involves the immersion of a thick blown in the crucible containing transparent glass of another color and equally large thickness. The superposition of thick transparent glass allows to obtain particular chromatic effects. The submerged was developed in Murano during the late thirties and was popularized in the fifties by Seguso Vetri d'Arte, directed by Flavio Poli. This process is a popular technique for vases, and is sometimes used for sculptures.

"Cold" processing

The "Cold" processes are all processes performed without proceeding with the complete melting of the glass.

Conterie

The "conterie" are rounded or sharp-edged glass beads, obtained by "lampwork" by cutting perforated tubes pulled in the furnace for about ten meters. The unperforated glass barrel is softened by the heat of the fire that comes out of a torch, then it is wrapped around a metal tube that gives the pearl the desired shape and finally decorated with the use of polychrome glass. The conterie differ from those worked in the past which were called margarites. Their processing was introduced in Murano in the thirteenth century by Cristoforo Briani and Domenico Miotti. From their numerous pupils a very flourishing industry was born that is still active today.

Enamel decorated

The enamel-decorated glass technique involves the use of colored compounds obtained with finely ground opaque and transparent low-melting glass powders, applied with a brush on the glass surface to create a decoration that can take on abstract, vegetable or figurative shapes. The decorated object is subsequently subjected to a thermal cycle that does not exceed 500 ° C, in this way the glass applied with a brush, softening, adheres permanently to the surface of the support glass. This type of technique has oriental origins and was introduced in Venice in the last decade of the thirteenth century with great success in the Renaissance.

Millefiori

The term "millefiori" defines a perforated or non-perforated barrel which has several concentric glass layers of various colors and shapes, usually flower or star-shaped. The first phase of the processing involves the use of open molds that imprint the different shapes each time according to each layer of different color and subsequently the pulling of the barrel along tens of meters. A particular type of millefiori cane is the rosette, which dates back to the 15th century characterized by star motifs in white, red and blue glass, in alternate layers. The millefiori cane is generally cut into sections called murrine. The segments obtained from a perforated barrel, after being ground, can become pearls. While the unperforated sections can be combined and melted in the heat of the oven so as to package plates or bowls and if melted at the bottom of a small hemispherical mass of crystal, paper presses or press-papier.

Grinding

Grinding is a technique, which has remained unchanged for many years, which allows the glass to be hollowed and is carried out in different phases. The first phase involves the use of a very rough wheel made of "80" grain silicon carbide, the second phase consists in adjusting the incision previously made with a wheel, also in silicon carbide, but with a finer grain "220", in the third phase we act with the extension and smoothing of the incision through the use of a natural sandstone wheel. In the fourth and last phase, the object is brushed with a cork wheel impregnated with a mixture of pumice stone and water in order to polish the engraving. When the work is done, the object is cleaned and made shiny with a cloth wheel wet with cerium oxide and water.

Mirror

The origins of the Venetian mirror date back to the Renaissance. The processing of the mirror is based on a glass plate, with a part coated with aluminum or silver, which produces an image by reflection of the figures that appear in front of it. Only between the end of the twelfth century and the beginning of the thirteenth did the diffusion of glass mirrors with a metallic coating and, with the Renaissance, Venice and Nuremberg became renowned centers for the production of such objects. In the 16th century, the most common way to make a glass surface mirrored was to apply a thin layer of reflective metal, often an alloy (amalgam) of mercury and tin. Later in 1835 Justus von Liebig discovered the chemical process of coating glass with silver which gave rise to today's mirror production techniques. The procedure consists in spraying, under vacuum, a thin layer of aluminum or silver on the lower part of the glass plate and waiting for the reaction by electrolysis. The metallic layer deposited on the side opposite to the reflective one is covered with a paint for protective purposes.

Melting glass

It is a very ancient technique, which also includes glass mosaic. Sections of glass of different colors are placed side by side on a ceramic fiber plate and melted in an electric oven in order to obtain a multicolored glass fabric called mosaic glass or murrina. On the plate are arranged fragments or glass granules of different colors that merge with the basic vitreous support. The operation can be repeated several times by superimposing the colors and creating a three-dimensional decoration.

Murrino glass

Murrino glass is one of the most ancient techniques, it is a second process that consists of a glass plate composed by heat welding glass tiles of different colors sectioned from polychrome rods, the plate is then modeled with the use of a refractory clay mold and can be further modified by taking the shape of a vase.

 

 

Taken from the website: muranovenezia.info    Murano L'isola del Vetro