Your Glass is Crass

Seasonal activities have kept me busy as a one fingered feather plucker before Thanksgiving, so I've been a bit lax in recanting the rest of the Italy trip. I'm about to start a few art projects now though and am faced with a dilemna. Maybe some of you can help me out with it.

The subject which I'm doing a mosaic of has very intense purples (violet cobalt manganese oxide pigments), but the only commercially available glass I can find with the color intensity of the object I'm trying to represent would be cobalt blue. So I've been hitting the color theory books and websites, trying to figure out placement or backgrounds that would make intense cobalt blue seem more like a shade of rich purple in context.

Here is an example Roman model boat of a cobalt blue glass in the British Museum from the first century. It's blue, but kind of purple as that glass often is. I like to think that 1900 years ago, someone served gravy from this.

While wading through all of the color theory information, I've come across some examples of how the human mind processes color and shape. Some of these examples involve motion, but many are just how the colors and shapes are processed.

For example, check out lilac chaser on Michael Bach's site.
This guy has collected several other visual phenomenon examples that are fascinating to me.

I'm leaning towards giving the cobalt blue a background of its inverse color in green. Given an unsaturated background of green, because of the way eyes process color with their red and green cones and rods, it should trick the mind into attributing more saturated red in the object done in cobalt blue (which is what I want, to play up the violet elements of the cobalt blue).

What do you guys think?

Another thing that I discovered while pouring over glass chemistry was a complete surprise. Back in the 20th century, they used to make glass with uranium dioxide in it (completely radioactive). This sounds like a horrible cancer causing express train to legal liability, right? Well it turns out that glass is a great radiation shield, so this radioactive glass is not the deadly killer I first suspected it might be.

Shining an ultraviolet light (as above) on glass made like this causes it to flouresce in a manner that even Monty Burns would be proud of. I've now taken to carrying an ultraviolet light with me everywhere to check for *ahem* flourescence.

Hot Piece of Glass

Not much new going on around here except work and being nominated for the highly distinguished Drysdale Award for the dullest blog over at Grant Miller Media so vote for me if you aren't too excited and drawn to my blog.

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.

Sirmione - Ancient Lake Fun, Part II

While driving from Venice to Lake Como, I had to make a long lunchtime stop at a unique spot in all the world. Sirmione is a geological oddity, a very narrow strip of land jutting about two miles out into the ancient Lake Garda.


It's kind of strange to walk for so far in one direction and see water on both sides. Last time that happened, I was on a cruise ship treadmill.


It was rumored to be the location of a villa of Catullus, a close friend of the family of Gaius Julius Caesar, but it was probably a different Roman dignitary who lived here in those days.

It makes military sense that the original villa builders would pick this spot because it is supremely defensible. Well, except from attacks of a flying or swimming enemy. The ancient Romans wouldn't have stood a chance against a nuclear submarine, right?

Here I am standing in the main 'foyer' of the villa. Behind me, as you might guess, is the lake. Apologies for my shoddy state in the photo, but I'd just been driving in Italian traffic half the day when this was taken.



















Below, you can see the 'marble beach' view out the 'front door' of 'the' villa... I'll bet they had some great parties out there, even though it would be tough to use a jet ski loaded down with a case of beer because it's so shallow.















The size and scale of the Roman villas makes my house seem so small...































They also had a neat little museum with a diverse collection of implements, mosaics, frescos and such.

















I promised some glass and smalti images a few posts back. Here is some off my 'stash' of mixed colors and an Orsoni sample board showing the standard pallette with a pretty large range of value and hue.















And here is the actual result (from my class) of that mosaic from the 6th century. I accidently put up a photo last time of just my empty easel with just the image I was copying in mosaic. Strangely, no one called me on it.

Glass (Vetro)

In deciding on a Venice itinerary for this fall, I made plans to stop by the famous Domus Orsoni in sestiere Cannaregio. This place makes the best glass pieces for mosaics, and is also famous for their gold leaf crystal. They have nice rooms to stay in, but there are more luxurious places with balconies and terraces on the Grand Canal.















But check out the great golden shower you can get in guest room four at Domus Orsoni...




















I used some of this same 24k Orsoni gold leaf glass in some 3" mosaics I'm making for the new pool to be constructed. The contractor asked if I wanted 'step spotting' tiles so drunk uncoordinated visitors wouldn't fall whilst getting into or out of the pool. Being the hands-on type of guy I am, I decided to make several small mosaics as 'step spotting' tiles and just have those set in instead of boring one color tiles. I'd cover the whole bottom of the pool myself if I had the time, but I want to do the decking and probably carve some statues in carrara marble. So, maybe I'll just let that 'ultimate mosaic' pool part of the dream go for now.

Here is one of the mini-mosaics using gold Orsoni glass, marble and a bit of porpyry in a picture taken from atop a ten story parking garage downtown to make it more dramatic. *dramatic music plays*

















Glass making in the Venice area has a long and profitable history. It has been made there for around 1000 years. From master craftsman to apprentice, the secret recipes of silica, lime, sodium oxide, arsenic, nitrate and coloring agents (or manganese oxide in the case of clear glass) in just the right proportions and in the correct order of processing have been handed down.

One of the Venice glass companies, Barovier & Toso, was formed in 1295 AD. They probably have one of the oldest corporate websites in the world too.

Hopefully, after Luciana's class in Ravenna this Fall, mosaic making with glass and smalti won't be so foreign to me compared with stone and marble. I tried using Leponitt cutters for the first time on the gold glass pieces on Sunday, and it was difficult. Leponitts are spring loaded pliers with two glass cutting wheels that come together to score the glass. Of course, I was using them more like tile nippers, handily crushing the glass underneath.





















If you want to check out a modern glass artisan, go to Valerie's blog because she knows more about it than I ever will. Maybe I can pay Valerie to kiln up some smalti so I don't have to lug back 100kg of glass on the plane?

Does anyone else like the iridescence that occurs on ancient Roman glass? After thousands of years, some of the elements such as copper based impurities float to the surface of the glass giving it the rainbow and shimmer effect. It always amazes me that there is so much Roman glass left, what with glass being breakable and the ancients living with stone floors. Maybe it's thicker?

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Ho fatto i mosaici per i scale della piscina. Usato lo smalti oro di Orsoni, lo spero non rende ciechi a causa del sole.