What is Glass COE?
So what is glass COE? You see it listed in auctions and Etsy, you hear references to COE, but what does it mean? Let's talk about it, and why it's important.
What is Glass COE?
COE, when talking about glass, stands for coefficient of thermal expansion. In other words, how much and how fast glass expands and contracts, based on its makup. Since different kinds of glasses do use different ingredients, each rod of glass has its own rate.
In general, you'll most often see the following COE numbers:
- 104 -- soft glasses like Effetre, Vetrofond, Lauscha, Double Helix, CIM, Precision...I could go on and on. It's by far the most popular type of glass for lampwork beadmaking.
- 96 -- Uboros, System 96 and CIM are three names you'll see most often, but there are others. And while some people include the Zimmerman and Richenbach glasses here, they really do have a COE closer to 94.
- 90 -- Bullseye is the glass of note here.
- 33-34 -- Borosilicate. Also known as pyrex and boro. Northstar, Glass Alchemy, Momka's are three of the top names in colored boro, while Simax and Pyrex are two of the clears.
- Other -- This category includes the real softies like Satake and Kinara, plus Czech (Ornela) glass. They have COEs anywhere from 106 though 120.
Glass Rods, Mostly COE 104
The most important rule if you don't want broken beads: do not mix glasses of two different COEs in the same bead. Although shortly you'll see some exceptions to this rule.
COE Versus Viscosity
Now if COE was all you had to worry about, life would be grand in the bead-making world. But sometimes you'll find that two glasses with the same COE don't play nice together. And the culprit is usually viscosity.
I have a hard time explaining viscosity with how it relates to glass, so I'll use an example with foods. Take a tablespoon of milk and a tablespoon of honey and pour them into a bowl. The milk pours out quickly, while the honey takes its time oozing out of the spoon. The honey is more viscous than the milk.
(Okay, it's not a perfect example, but now you can get a mental image of viscosity.)
A good glass example of viscosity is comparing Effetre pastel white against Lauscha clear. Effetre pastel white melts fast and can get drippy very easily. Lauscha clear is much stiffer and is more like honey when it melts.
While I don't know for certain, I suspect that viscosity effects COE; in other words, a more viscous glass has a lower COE. And within a glass type (example, glass with a COE of 104), the tolerance is generally 2 points. So what that means is that a glass can be labeled 104, but actually have a range of between 102 and 106.
So, if you combine a 104 glass that's actually 102 and a 104 glass that's actually 106...you get incompatibility and a cracked bead.
Is it Ever Safe to Mix COEs?
I want to say first off is that there is a lot of controversy over this. Some say that you never, ever want to mix glasses of two different COEs, even in minute amounts.
Others say that it's acceptable to mix a tiny bit of a leaded glass (usually a frit made from a 94-96 COE glass) with, say, a base bead of 104 glass. The emphasis on the word tiny.
The only thing I can say about this is from my own experience as a bead-buyer and a bead-seller. I have beads from around 2002 that have some frit on them that appears to be the 94-96 glass that are unbroken. I have made beads that include a tiny bit of 94-96 COE glass that for 5 years haven't cracked or split.
Does that mean they won't crack or split 20 years from now? Don't know, but you can check back for a report then!
In my case, I work mostly with COE 104. Therefore, I label each and every rod that is not COE 104 with its color and COE. Glass can all look the same after awhile; best to play safe.
Well that's it for today with the topic of "what is glass COE". Here are some examples of lampworking glasses in various COEs and colors.
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 Glass Rod Flint 5mm od x 295L 5 lb approx65 pcs  US $25.00
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 Glass Blowing Boro rod Tubing Beginners Bundle Lampworking US $23.25
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 Northstar glass glasstique off color rod glassblowing US $29.95
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 13mm glass rod US $30.00
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 104COE Moretti Randomly Selected Glass Rod Assortment 15 Pounds 65 SALE US $183.25
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 Glass Lampwork Bead Making Design Kit Tool Glass Rod DVD Torch DIY Fireworks Lot US $189.99
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 Mercadante Cobalt Blue Borosilicate Glass Rod 1lb 25mm US $.99
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 Bullseye Glass Transparent Rod 1 4lb COE 90 Lampworking US $6.63
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 Bullseye Glass Opalescent Rod 1 4lb COE 90 Lampworking US $6.63
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Chinese Lampwork Beads
Chinese lampwork beads seem like a real bargain at first. You can get so many for such a small price. But are Chinese lampwork beads really a bargain? Let's talk about it.
How the Beads are the Same
In some ways, these Asian glass beads are made just the same as the handmade lampwork beads here are in the States, Canada, Australia, etc. Hot glass is wound on a mandrel, forming a glass bead. The beads are cooled, then removed from the mandrel. Ta-da! A glass bead. So far, so good, right?
How Chinese Lampwork Beads are Different
Not so fast. There are several differences between the Chinese lampwork beads and the handmade lampwork beads made by artisan lampworkers. A quick rundown includes:
- Chinese lampwork beads are mostly made by women and children at low wages. Because it's their livelyhood, the emphasis is on quantity, not quality. (While there are probably exceptions to this rule, I haven't heard of them yet.)
- They are not made as carefully (quantity thing) and very often have rough holes that can cut beading wire.
- The beads are not annealed, which means they are subject to cracking and just plain falling apart. (Here's the post where I talk about why annealing is so important to lampwork beads.)
- The beads are generally not cleaned of the bead release left after removing the beads from the mandrel. This means that the bead release will eventually dust off onto you.
Now you are seeing the differences as to why the Chinese lampwork beads are much less expensive than the handmade lampwork beads made here.
Are Chinese Glass Beads Ever Appropriate?
There are times when these inexpensive glass beads may be appropriate, such as rainy day crafts projects for children. Or for teens who want a quick piece of jewelry then just as quickly discard it. The cracked beads can be made into mosaics.
But if you want jewelry that lasts, or you plan to sell your jewelry creations, you want the well-made artisan glass beads.
Locally, you'll most often find the Chinese lampwork beads at craft stores like Michael's, JoAn, Rag Shop, Hobby Lobby, etc.
The Artisan Beads
Below are some examples of some lovely, properly-made and annealed handmade glass beads. You can also find a .
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 ROA Lampwork 4 Opaque Lime Ruffle Disc Glass Beads SRA US $5.98
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 JMoore Handmade Glass Lampwork Beads MINI SET MS 395 US $3.55
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 ROA Lampwork 2 Dark Tsp Lime Ruffle Art Disc Beads SRA US $2.49
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 Lampwork Glass Beads Blue 3 Flower Heart Pendant 1pc US $2.99
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 Handmade Lampwork Glass Spacers Beads Ivory US $10.00
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 Lampwork Rectangular Beads Turquoise Round Beads US $9.99
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Bead Kiln
A bead kiln is another of the essentials of lampwork bead-making. It's a fairly big investment, but you don't want to sell your beads without one. Why is a kiln so important to creating handmade lampwork beads?
Purpose of the Kiln
Jen-Ken Bead Kiln (Click for larger image)
The purpose of the kiln is two-fold. First, it keeps your beads warm as you are working; without proper warmth, the beads with suffer thermal cracking.
Second, the bead kiln de-stresses the glass bead. You see, when a bead is made, the glass is stressed -- from winding it around a mandrel, from uneven heating, etc. The kiln evens all that out and allows the glass to strengthen into its new shape.
Beads made without the benefit of the kiln are far more likely to suffer cracking and fall apart.
Garaging Versus Batch Annealing
Annealing is a term that refers to using a kiln to de-stress it. Sometimes kilns are referred to as annealers, especially kilns built for the sole purpose of bead-making.
Garaging means that the kiln (annealer) is on while you are making the beads. After you make each bead, you pop it in the heated kiln to keep warm. Of course warm is a relative term -- at 900+ degrees, I'd call that hot! 
Once the bead-making session is over, the kiln keeps the beads hot for a per-determined length of time, then slowly decreases the heat over several hours. This is done slowly so the bead isn't stressed again.
Batch annealing means that you don't use a kiln while you are making the beads. The beads are kept warm using a fiber blanket or a crock-pot filled with vermiculite. Once the beads are cool, they are gathered together and placed into a cold kiln. The kiln's temperature is raised slowly (so the beads don't shatter from the sudden heat). After the beads have reached the annealing temperature, it's the same process as if they had been garaged.
There's a great debate in the lampwork world as to if batch annealing makes beads as strong as garaging. I won't get into that arguement, other than to say that I think it doesn't matter so much for smaller spacer-type beads. Larger beads may be a different situation.
Buying a Bead Kiln
Bead Kilns are definitely a pricey part of lampworking, but they are essential. As I mentioned before, you do not want to sell a bead without it being annealed first.
There are several manufacturers of kilns -- Jen-Ken, Paragon, Skutt to name a few. They all make annealers in different sizes for different purposes. Two popular lampworking kilns are the Jen-Ken Chile Pepper and the Paragon Bluebird.
I personally have a Jen-Ken kiln with a bead door that I bought on ebay and I love it (see the photo above). Others have their favorites, based on the type of glass work they do. There are even kilns built specifically for lampworking that many swear by.
As to price, a good bead kiln with a digital controller will run anywhere from $500 to around $1,000. I do not recommend a kiln with an infinite switch; they are not nearly as accurate as a digital controller, and you have to "babysit" an infinte-switch annealer.
Below are some kilns from the ebay seller I bought my kiln from, so you can take a look at the specifications and get an idea of what you might need.
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 Wash Away Stubborn Kiln Primer Residue No Scrubbing US $17.99
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 Take A Part Glass Fusing Bead Kiln w Collar Flip Door US $675.00
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 Take A Part Glass Fusing Bead Kiln SQUARE w Flip Door US $640.00
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Lampwork Supplies – The Torch
Among the lampwork supplies, the torch is probably the most important piece of equipment. No torch - no melting glass. No glass -- no lampwork. Here's a little information about the lampworking torch.
I'm writing this for anyone who either has no or little knowledge of lampworking.
The Torch Explained
Bobcat Lampworking Torch (Click for larger image)
There are several kinds of lampworking torches, ranging from fuel-only to propane-oxygen. Different torches give off different levels of heat, and so are suited for a variety of glass projects.
The torch you see here is called a Bobcat. It's a propane-oxygen torch that's well-suited to some of the higher COE (90 and above) glasses. (While I have done boro on this torch, it's a much slower process.) The red and the green knobs you see determine the oxygen and propane flows.
An oxygen-propane torch uses propane (or natural gas) as a fuel, and oxygen as an accelerant -- makes it burn hotter. Oxygen can come from oxygen concentrators, oxygen generators or oxygen tanks. My setup uses 2 oxygen concentrators.
While a generator or tanked oxygen would provide a hotter flame, the cost and ready supply of oxygen made me choose concentrators.
Single Fuel Torch
When I first started lampworking, I used a single-fuel torch called a HotHead. It's called a single-fuel because it uses propane only - no oxygen. The torch is quite inexpensive and a good choice for someone who wants to try lampworking, but doesn't know if he or she will like it. That way you don't lay out a big expense right away.
A HotHead works produces much less heat than an oxygen-propane torch, so it's slower to melt the glass rods. This can be an advantage for a beginner, as it gives a bit more control over the way the glass moves.
Most lampworkers eventually move up to an oxygen-propane torch, but there are some experienced lampworkers out there who prefer it and produce gorgeous work on the HotHead.
Torch Price Ranges
Keep in mind these prices are estimates at the time of this writing.
- The HotHead is around $40.
- Two popular beginner oxygen-propane torches are the Cricket, Minnow and the Minor. They are in the $170-$200 range.
- A little further up are the Bobcat, Betta and Mega Minor. They are in the $200-$250 range.
- By the time you get to the Lynx, Mid-range and such, you're talking anywhere from $350 to $500.
And from there on up -- well, you can spend $600 up to a few thousand for a torch.
Lampworking Supplies - The Torch Final Notes
These torches are h-o-t! You need to be very careful because you can get a serious burn from even a HotHead. And because you are "playing with fire", you need to observe common sense rules, like tying back loose hair and removing all flammable items from around where you work.
There are other lampworking supplies that I'll talk about in other posts (glasses, mandrels, types of glass, etc.). But of all the lampworking supplies, the torch is the most essential.
I hope you've enjoyed this introduction to lampworking torches.