Scum on the edges
This is a persistant problem for many fusers. The cause is usually ginding the edges with too coarse a bit. When you grind, you need to use a fine bit on the last step and even then, use a devit agent. I use clearcoat, but the others are fine.
Also, you mentioned “cheap glass”. I assume you are not using a glass from Hobby Lobby. If so, that can be a possible additional culprit.
Web Site http://www.kaiserglass.com
Glass Classes: http://www.Kaiserglass.com/classes.html