Muranology, the first on line glossary about Murano Glass from A to Z: Letter O
Welcome back to Muranology, the first on-line glossary-storytelling about Murano Glass. Today it is the turn of “O”, and after the “N”, just by chance, we are still in the topic of the natural elements taking part in the glass making process: last time we mentioned the importance of the natrium (NA in the periodic table), a mineral, and now we have the ORO (Gold, or “Au”), which is a metal.
Do the gold or other metals play the same role as the minerals in the glass making process?
No, the soda or the potash, for example, are incomparably more important than the metals, as it is a “fondente”, which makes possible to decrease drastically the melting temperature of the silica sand (SiO2) from 1700° to 800°, while the metals are not a condition sine qua non. A furnace cannot work without the soda or the potash, but could perfectly work without using the gold or other metallic components in its glass formulas, although it would be a great loss.
Why gold, despite being not a fundamental element to obtain the glass, is still so important?
The Murano factories purchase two different kinds of gold: colloidal gold (sol or colloidal suspension of nanoparticles of gold in a fluid) and golden leaf, 24 karate. The colloidal gold is used for producing the ruby red, the most expensive and precious color, previously mixed with all the other components inside the oven. The golden leaf is highly appreciated for its beauty as a decoration. It is quite frequent to see the master laying a golden leaf on the “bronzin” (a working table made of iron) and, then, rolling the incandescent mass of glass on the surface, thus the gold is merged into the glass, before being blown and/or sculpted. At the end of the cooling process, the glass-item (often a non-colored, crystal-glass), will be characterized by a magical shiny light, sometimes with very tiny spots, looking like “golden prey”. The golden leaf is tipically used also in the art of the glass-mosaics, as the famous ones inside the St. Mark’s Basilica or inside the amazing (and less known) church of San Donato, in Murano.
Is it possible to use the artificial golden leaf, as the ones used for the Carnival masks or the decorations on wood, or adding other chemical components instead of the gold?
Fortunately not! When you buy a golden Carnival masks, a professional artisan will always tell you whether it is real golden leaf, because the artificial gold, in this case, seems to be almost indistinguishable by naked eye, but the art of glass is completely different from the papier-mache or the decorations on wood. It is a matter of chemical reactions. Until now, it seems impossible to produce a typical Murano red ruby color without using the colloidal gold, while the artificial golden leaf would never work at such high melting temperatures.
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