Now the grit rather than playing boulder and rolling and forming pits, the grit will be embedded in the pads and perform more like sandpaper. Once the surface becomes 'smooth' enough, we will start the true polishing of the mirrors. The prepolish tool was carefully watched during this phase since no one in the group had ever used these polishing pads before. We had several concerns. The tool form was made from the rough ground mirror.
Plaster is a difficult surface for adhesives to stick to.
If the pads came loose between the mirror and tool, bad things could happen. They seem to have done well however. Members watched while the grinding continured and the glass got clearer. For the final part of this stage, we used polishing rouge on the felt pads rather than the 9 micron grit.