I thought I would talk about how glass rods are made in Italy. I think I should mention that information about glass making in Italy and anywhere else for that matter is intensely guarded by those who make their living from it. Back in the 15th and 16th century they use to kill anyone who tried to take this kind of information away from Venice and Murano.
The beautiful colored glass rods we are use to, start out as fine toxic silica dust with a few other mineral elements add and only becomes what we are familiar with after much processing.
One of the things that blow’s my mind is the fact that companies like Effetre / Moretti have to have all the supplies that they use to make glass brought in by small cargo boats. They store all these components in a portion of their huge warehouse complex. The components mostly arrive in paper bags and get moved to big labeled bins in the mixing room. From the bins the components get shoveled into mixers and blended. The minerals that end up in the glass formulas are weighed on counter-balanced scales and the weight of these elements is subject to the influences of the ever present humidity of the Venetian Lagoon where Murano is located. It is so humid on Murano and Venice that the stucco that covers so many walls in the area seems to peel almost as soon as it has been repaired.
After the glass formula is mixed, it is transferred to big bins that can be lifted by forklifts and these bins have lids to keep contaminates out of the bin. The powder mix is loaded into a crucible in a specific kind of glass furnace designed for glass melts. A crucible is a heat resistant container that is made out of a very dense ceramic material that is very expensive and they have a limited life expectancy due to the prolonged heat exposure.
Every time I went to Effetre to interact with the factory, I was always struck by the beauty of all the piles of different color glass cullet (big chunks of glass). I would pester them to sell me these glass chunks and I could not figure out why they were so reluctant to do so. Later I found out that it is customary to throw same color glass cullet into a new batch of glass in the furnace because the cullet absorbs the heat and causes the powder components to melt faster.
The factory gets their cullet by pulling out the last few kilos of molten glass out of a finished crucible and put it into a big three legged steel bowl like container to cool in the open air. As the glass cools, it fractures into chunks and when it is completely cool they dump the cullet out on a concrete patio between the warehouses. The cullet sits in this patio until it is needed for the next appropriate glass melt.
When the glass in a melt furnace is ready to be made into rods, the factory lays out dozens and dozens of small wooden slates down the long walk ways between groups of furnaces to provide a place where the long cane pulls can be laid so that it doesn’t touch the cold concrete floors and get thermal shocked. Until I saw this being done, I couldn’t understand why there were these black burn marks on some of the hand pulled glass rods, but when you know that the black marks are caused by the hot glass touching the wood slates it all makes perfect sense.