Thursday, January 27, 2011

Glass Color

People often ask me how I get my glass to be the right color. Some people ask me if I paint the glass or if I add chemicals to the glass. So I'm going to explain here about recycled glass colors. Let me first off say that even though I can often be found with a variety of liquor bottles in my possession, I don't drink alcohol. However, alcohol bottles are the most abundant type of bottle out there and come in the biggest variety of colors. That’s right; I get my colors from the bottles themselves.

There are a few ways stained glass gets its color. First of all normal glass is clear which is very convenient because it would be weird to look out of colored glass windows all the time. To get different colors of glass manufacturers add metal oxides to a batch of molten glass. Different metal oxides in different ratios produce the myriad of colors that you see in stained glass. These colors can range between opaque to clear, dark and light and everything in between. There are several companies out there that specialize in producing consistent colors for use in art glass.

This is a good time to talk about compatibility. The companies that make art glass usually try and make their glass compatible. This means that two different pieces will fuse together when heated and when they cool they will maintain a congruent, cohesive bond. Basically glass expands as it is heated and as it cools it contracts. Depending on the chemical makeup of the glass, i.e. the different metal oxides mixed in, the glass may expand and contract at different rates. If you try and fuse two pieces of glass that are not compatible, they will expand and contract at different rates and a cohesive bond will not form resulting in cracking and in extreme cases explosions. The trick here is to produce glass that is not only compatible, but also in a range of colors. The swirly colors seen in a lot of stained glass is produced in this way.

Bottle and window manufacturers don’t care if their glass is compatible with others, they only care if their glass finishes out structurally and visually sound. This is why people usually don’t fuse recycled glass; it just isn’t compatible. Because some of the metal oxides required to get certain colors are expensive (silver and gold for example) there are several colors that you will rarely see in “throw away” liquor bottles. Reds, yellows, oranges, and purples are rare in bottles and are usually reserved for art glass or more expensive containers and vases.

Another way glass is colored is by painting it with fuseable glass. If you look at stained glass in churches and see faces that look like they are painted it is because they are. Don’t be fooled into thinking that this is a cheap trick because it usually isn’t. Specially trained glass painters practice for years to learn to paint with enamels on glass. Enamels are basically powered glass. The artist will paint on the glass and then fire the glass in a kiln to fuse the enamel onto the glass. The end product truly is “stained glass” that won’t scrape off and can’t be washed off.

The last way glass is colored is by painting it with regular paint. This is the cheapest and worst way to color glass. Basically the glass is painted with normal paint, and that’s all. This kind of paint will eventually come off because there is no chemical bond to adhere it to the glass. If you were to put painted glass in a kiln it would burn of the paint and you will get a dirty clear glass as a result.

As a result of all this, I have a limited pallet of colored glass to choose from. Most of my glass comes from bottles including the ones shown here. (No, I am not endorsing any of them.) Sometimes I use different colored (usually white) light sconces. To get the hard to find colors I search the thrift stores for vases, plates, cups, etc. Everything I use has to be cut with my saw and then fired flat in the kiln before I can use it in stained glass.


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