How do you eliminate this?
Well, this is my method. Use a black coated copper foil and a big marker (oil-based). Just mark all edges of clear glass BLACK. Check it by looking through each edge at an angle to make sure that unwanted glare is not there. If glare can be seen, mark it again. Let it dry and tape it.(I cut and mark several pieces at once and let them dry while cutting and marking next set, and, tape the first set together)

It is a nuisance job, but, it is much easier than firing! This little extra work makes your work different from others. This method proved to be effective after 20 years since I have tried it first. So, I presume that the effect is permanent.

One weakness of this method: your hand will be in mess after the work. In marking small pices, marker gets on all over your hand .

If you have a better way, I would very much like to hear it. I would like to keep my hands clean.