There is an advantage of doing compatibility testing on your own.
If you find that certain glass has the same COE, there will be a broader range of colors and textures available for you to fuse.
But, remember, just because the pieces are compatible this time, doesn't ensure that new pieces of glass purchased will have the same COE, unless it is compatible tested by the manufacturer.
If glass is not compatible there will be cracks or lines where the two glasses come together.
Over time, these cracks will increase and eventually the piece will completely separate.
If this should occur during testing, then obviously the two pieces of glass are not compatible.
More subtle problems aren’t as obvious, and will need to be discovered through testing.
To conduct a test on your own, you will need to cut some small squares of glass to be tested.
You should note the COE of all glass pieces.
After fusing the pieces together, allow them to cool completely.
If they have not cracked, examine the glass piece between two strips of polarized film.
Hold the piece sandwiched between the polarized films over a light.
You can use a pair of polarized sunglasses.
These are the glasses they give you after you have cataract surgery.
You will need to rotate the lenses so that they are at right angles to each other.
Don't allow much light to shine through.
Take note of the edges of the glass where all the pieces come together.
No glow around the edges of the pieces means they are compatible.
The larger the glow, the more stress there is on the glass.
This built up stress is likely to cause your glass to crack or break over time.
Have you seen the
Compatibility Test Card
from the Kaiser Lee website?
This handy little card will help you determine if unknown pieces of glass are compatible.
The price of this card is about $10.00.
If you would like to see a demonstration of how this card is used, check out the
There is a simple test you can also try.
This will require you to use a torch.
Take two equal pieces of glass and fuse both pieces together using a torch.
As soon as they are joined together, pull the pieces apart.
The glass should pull out in a string.
If the pulled string stays straight, the glass is compatible.
If the pulled string bends then the glass is not compatible.
Compatibility testing is a good idea, especially if you don’t know the COE of your glass.
By doing a test on your glass you will be able to see any changes in the glass during fusing.
If in doubt, always conduct a test to be sure of the compatibility.
It takes time, but will save you the heartache of ruining any fused projects.
Return from this page to one of the following pages:
Compatibility Testing to Glass Fusing Made Easy
Fusing and Slumping