Now how did you get the mirror back black? I seem to blast off the reflective at best, and explode the glass (tiny pockets) in thick lines at worst, but nothing added yet. I must try the molybdenum sulphide and the black spray paint, and the rustolem primer on tile… too many things 
Beautifully, What was the kerf you used?
What other settings did you use ?
Sorry for the late reply.
I used the laser on the back of the mirror to remove the coating.