glass scales

[Matt Sachs]

I have an HH Roberts Bed mill with an Anilam 3300mk equiped with glass scales. I have had an intermittent problem with the x axis gaining betweeen each move. I cleaned the X axis scale and it worked great for a day. This morning while it was homing, the x axis surged.
Rick at Anilam was very helpful in isolating the problem. I switched the leads on the X and Y axis and every thing worked (but back wards) Then I put the wires back where they go and the mill works fine. So I guess the problem was a bad connection where the leads plug into the back of the mill.

The mill is working fine now so my question is this.
When I cleaned the scale there was a series of little rectangle stickers on the glass. When I finished cleaning it, they all fell off.

How bad it that ?$
How does a glass scale work?

Thanks Matt