I wasn't carefull enough in my description of the bubble. It is not in the glass, but rather in the slurry between the mirror and the tool. If I understand things correctly, this indicates that the mirror is not yet spherical.
So my question is should I ensure that I have a spherical mirror as best as I can tell before moving on to the next finer grit, and if so what is the best stroke to use ?
Thanks, Gary Lowell glowell!sgi.com