The most frequent question that I get is “Can I fuse different kinds of bottles together? I saw someone else doing it and it seems to work.” followed by “My fused bottle projects are breaking in the kiln or later, how do I fix that?” See the pattern? So, I thought I’d show you what is happening IN the glass when you fuse different bottles together.
I started with clear bottle glass, I fused the glass from one bottle with itself as a control. (I also did a kiln carving pattern with it because I like to multitask.)
Then I assemble two mixed bottle glass fusing projects. Each one uses clear glass, two pieces from the same bottle, and different colors of bottle glass. The first one has a ring from a brown bottle around the bottom of a green bottle and I sandwiched it between two sheets of clear (the top isn’t on yet in this photo).
The second has a clear base, a lime green ring with a cobalt ring inside of that, and a lime bottle bottom inside of the cobalt ring, with the other clear piece on top.
Then I fused them using my handy full fuse schedule.
And look at that, they SEEMED to work, now let’s take a look inside. Using a polarized filter, I’m going to check for stress in the glass. Internal stress is a strong indicator of incompatibility or poor annealing. Either way, your project is headed for cracking eventually.
Let’s start with our control project. If it shows internal stress, then we have an annealing problem. We know the glass is compatible, because it came from one bottle and glass is always self compatible.
Stress shows up as flares of yellow or white in the glass. I think it’s safe to say there is little or no stress in our control project. Sweet! Now, let’s look at our mixed fused glass projects.
This is problematic. The flares in the glass are showing substantial amounts of internal stress. The solid yellow circle under the lime green ring is particularly troubling, as are the flares around the brown ring.
So, my conclusion is, although it SEEMS to work, and the results are pretty, I would be uncomfortable selling something that I knew had problems and would likely break later. There are so many, many other techniques and things you can do with fused bottle glass that I would not recommend mixing bottle glass for fusing without testing for stress and compatibility.