In unrelated news, I'm committing an excellent book to memory, 'The Arts of Antioch: Art Historical and Scientific Approaches to Roman Mosaics and a Catalogue of the Worcester Art Museum Antioch Collection'. This book delves deeply into the chemical makeup of the ancient pieces of the mosaics found in Antioch, or modern Antakya, Turkey.
I might just get a friend with a kiln to cook up some of the recipies that this book has (especially after spending about 800 euro on art glass last month). More importantly though, being able to control every aspect of the glass creation is what I find as the most appealing. Here is the furnace at the Orsoni factory in Venice which I saw in October.
Finding this place in Canneregio was particularly difficult for me because 1) my GPS had the wrong address to begin with, 2) I had to go under the Sottopassageo Vedai, which was basically like a literal hole in the wall down an alleyway, 3) I didn't see any kind of sign other than the little bronze plaque by the doorbell (I blame this problem on US advertising where the signs are all at least human sized for every place of business), 4) I had had a half liter of red wine prior to starting out.
Most people don't know that many ancient Roman mosaics contain quite a bit of opaque colored glass. Usually wind dirt and erosion makes it look kind of like stone. Also, they put so much calcium and lime in some of the colors, it really does look more like a stone-based glass paste than the highly reflective mirrored glass of the Hubble telescope.
As a quick refresher, glass is made by heating up silica (sand), soda as a 'flux' which lowers the required temperature to melt the sand (sodium based, not soda like a coca cola), and lime. Sometimes other elements like calcium, copper sulfates, lead oxide, and stibnite were added to make the glass more opaque or to get certain colors.
The other variable in obtaining the colors is the controlled time that it takes for the glass to cool, or 'annealing'. For reds and oranges, the internal crystals have to grow just right. Several hundred years ago, only certain specialty shops had the knowledge to make red and orange glass. Lawrence Becker who is a co-author on the book above, conjectures that some of the pale blue and green glasses were actually failed attempts at producing finer and more expensive red glasses.
One of these glasses used by the Romans was the 'Natron' based glass, so named because of the place where the soda stone was found in Egypt (Wadi Natron). Did you realize that on the periodic table of elements, sodium is 'Na' because of this? I thought so.
You also have the low magnesium / high potassium glass, or LMHK, which they've traced the source of the soda in this one back to certain plant ash.
For your amusement here is a video of someone pouring a small amount of glass.
Now if you'll excuse me, I'll be pouring a wine glass for tonight.
