We hope you enjoy these articles on Glass Art. There is so much more to know, of course, and we will recommend books and web sites to you so you can grow into your knowledge. We want to give you some basics so you can get started, have some success and be encouraged to go on to more difficult techniques and processes should you choose to do so. You may feel, at this moment, that glass art is mysterious and scary, but once you learn a few basics, you too, can find yourself making jewelry, plates, bowls and many other items. And then one day, you will realize, just like we did...’I’m addicted to glass!’ And if you really want the Short Cut Version - click here - but do come back and read all of our articles. The more you know, the better your chances for success with your projects.
Simply put, Glass Fusing is the joining together of 2 pieces of glass by melting them in a kiln. This process can be a TACK Fuse, where the two pieces of glass do not completely melt into one solid piece, but instead the glass on top of the bottom one comes out of the kiln with a 3D effect. In a FULL Fuse process, the two pieces of glass melt completely together to form one solid piece. The firing temperature for the tack fuse is between 1350 and 1425 degrees or full fuse occurs approximately between 1465 -1550 degrees F.
SLUMPING, SAGGING and DRAPING your glass art AFTER the fusing firing occurs at even lower temperatures, between 1300 and 1450, depending on how much you want the piece to melt for the effect you desire. Many techniques go up to around 1250 degrees and involves a hold time of anywhere from 10 minutes and up to 2 hours depending on the mold and the desired effect.
Other kinds of glass art firing are often at higher temperatures between 1480 and all the way up to as hot as 1800 degrees, but let’s focus on the techniques and processes for Fusing, Slumping and Sagging. Once you begin to understand these and have success with them, the more complicated techniques will still be there for you beckoning you to come and play.
If you have been doing ceramics and pottery, you are going to learn that glass fusing firings take place at cooler temperatures than you are used to and in a much shorter firing time. Now, that’s a bonus! Potters who are working with stoneware or other high-fire clay bodies are usually firing at Cones 5, 6, 8 or 10 - temperatures over 2100 degrees. Low Fire Pottery, such as most Paint Your Own Pottery Studios and home based Hobbyists use, are firing their kilns at Cone 04, if turning their green ware into bisque, or most of the time firing to Cone 06, about 1830 - 1835 degrees for their low-fire glazes. So you see, glass firing is done at cooler temperatures, for the most part.
We can say that glass firing and temperatures have 3 stages to go through:
1) From room temperature up to about 1000 degrees. Glass is still solid. It will start the melting process that will cause it to expand as it gets closer to the 1000 degree temp. It must move through this stage at an even rate to keep it from suffering thermal shock that can cause it to crack or break.
2) Once the temperature inside the kiln gets above 1000 degrees F., glass begins to soften and melt, and the look will start to change. The glass becomes more stable and around 1200 degrees, you can start doing different kinds of glass artwork.
3) From 1200 degrees and up, Draping, Slumping, Tack Fusing, Full Fusing, Frit Casting can all take place. And at temperatures over 1500 degrees, as the glass becomes more and more molten, even more advanced techniques such as Pate de Verre, Combing and Glass Casting can occur.
There are many different kinds of glass. And you need to know that they don’t all work together in glass artwork. There are so many different manufacturers of so many different kinds of glass. There is thick glass, standard glass, thin glass, transparent and opaque glass, glass that has coatings such as dichroic or iridized. All of these glasses have different compatibilities and understanding those compatibilities and which ones can work together will aid you in your success. Many glass students run out after their first glass class and buy window glass or stained glass and think, ‘boy, oh boy, I just saved a boatload of money on my glass’ and then they wonder why they are disappointed with the results. Window glass, sometimes called Float Glass and Stained Glass, sometimes called Art Glass, is very different from the glass used in most fused glass art. They can be used to make glass art with great results, but not necessarily in the processes we will be using for fusing, slumping, sagging and frit casting.
Let’s discuss for a moment what happens when glass melts. It expands as it gets hot and it contracts when it cools and the rate at which is expands can be measured. We’re not chemists or physic majors, (well, maybe some of you are!), but just understand that different glass expands and contracts at different rates. Although minute, these rates can have an effect on your art if you are using two different kinds of glass, one melting at one temperature and one melting at another and then contracting at different rates, as well.
So we measure the rate of expansion and the glass world calls this the Coefficient of Expansion which you will hear referred to as the COE. Bullseye glass, one of the glass manufacturers, makes glass that has a COE of 90 and that is COE 90 glass. Most of the glass art world seems to use COE 90. In galleries, museums, glass jewelry stores, you are most likely viewing COE 90 glass. Spectrum, another glass manufacturer and the glass we carry, makes glass that has a COE of 96. Perhaps you’ve heard of System 96? This is becoming extremely popular even with the die-hard COE 90 glass artists as more and more people realize how easy it is to work with when doing glass. You know those Pyrex cooking glass you have in your kitchen cabinets? Their COE is only 32. Window glass, sometimes called Float Glass, has a COE of about 84, as does Stained Glass. Effetre or Moretti manufactured glass, which is used for bead making, is COE 104.
You probably are never going to measure the COE, not in your home or studio. Just know and realize you want to be sure the glass you are trying to ‘put together’ into a beautiful piece of glass art must be the same Coefficient or COE. And you can simply buy our pre-packed kits and assortments. All of our glass is COE 96 except the cat whiskers or enamel threads. But we’ve done enough testing to know they work great with jewelry, tiles, plates, bowls and all our other packages and kits.