Soda/lime vs Borosilicate

Back when I first started lampworking, I had no idea there were different types of glass. In fact, I didn't even know there were different glass manufacturers. All I knew was that I needed something called "Effetre." No one ever told me about COE.

Now I own glass from many different manufacturers - Effetre, Vetrofond, Creation is Messy, Lauscha, Reichenbach, Devardi, Gaffer, and Double Helix (I may be forgetting some!). This doesn't even include all the frit, shards, or murrini makers I've purchased from. It is amazing how far I've come!

Soon after the start of my lampworking career I learned about COE. COE is the coefficient of expansion; glasses have to be the same COE to be compatible. All the glass I was using was COE 104, and it was called soda/lime glass. There are exceptions; for instance, glass with a COE of 96 (such as Reichenbach and Gaffer) can be used sparingly in 104. However, there was another type of glass I learned about, too. It had a COE of 33! It needed a lot of heat, and the pieces were generally bigger; most of what I saw were detailed, complex sculptures, and pendants where the design moved up and into the glass....how did they do that?? This glass was called borosilicate. I was in awe and I looked up to boro workers with revere. I knew that was something I would never do. I couldn't get a torch that big, or have enough heat. I couldn't create things that incredible, or that difficult. After all, I was making tiny 1/2" beads on my starter torch - a hot head.

Things change. I upgraded my torch to a bobcat and learned that on my 5lmp oxycon I could do small boro. That was kind of cool to know...you know, just in case. But it wasn't like I would really do boro. Then, some boro shorts were put up for sale.; I thought I would just get them to try later. Finally I succumbed to my curiosity and sprung for the eyewear - shade 5 Boroscope fit-overs - and dove head-in.

The difference is amazing! The glass takes much more heat, for one thing. I knew this but nonetheless I was very surprised. The glass gets so hot that I can feel the heat on my face; something that never happens with 104. Also, the glass is very stiff. It is harder to get the fluid, liquid-like shape that is so easy (sometimes frustatingly easy!) with 104. There is an advantage, though - that stiffness makes it easier to heat and shape tiny parts without melting down your entire piece. The stiffness also makes implosions a piece of cake.

Borosilicate doesn't shock nearly as easily, making large sculptures possible. Even with my limited oxygen supply I was able to create a 68mm seahorse sculpture with ease. You can put the rods right in the flame with no shattering, and you can make components of your piece then set them aside to use later without the risk of them cracking into bits. The first few times I heated a boro rod, I held my breath, leaned back and turned my face a bit, shoved the tip in the flame and flinched. If I did that with soda/lime, I would have frit all over the floor. It took some getting used to!

So with all these benifits to boro, why use soft glass? There are several reasons. First, the borosolicate pallete is seriously limited. There are a few manufacturers, but none of them have the extensive color lines that the soda/lime manufacturers do. Along those same lines, the soda/lime glasses are, generally, much brighter colors.

Second, soda/lime glass is much cheaper. Sales aside, you can get a pound of standard soda/lime color for $13-15 per pound. Silver glass is expensive (up to $100/lb), but it is not, by any means, a necessity when working 104. Add sales into the mix, and you can buy 104 glass for as little as $2/lb. Borosilicate, on the other hand, is quite expensive. Generally you can expect to pay $10 or so for a quarter pound of glass; a large percentage of boro colors are $50 or more per pound.

The third advantage is the cheaper start-up. If you want to start with 104, you just need a hot head torch ($40). To do boro, though, you'll have to have a surface mix torch (starting at about $200), and an oxycon (starting at about $250).

Finally, another 104 advantage is the fluid motion of the glass. It makes it easier to shape small pieces, wind onto a mandrel, and make smaller details on your work.

I love 104. I've been working it for 3 years and have a very nice collection of glass and "fun stuff" to use. I love having that extensive color pallette and putting details on my beads. There is so much I can do with soda/lime glass! However, I now love borosilicate as well. It fills a gap for me; I can do implosions and sculptures, which are things I tried repeatedly to do with soda/lime and failed. I now feel like I have the best of both worlds, and I have an array of possibilities ahead of me.

Boro Seahorse Sculpture