Jim had taken some wood and built a jig to allow him to pour the melted pitch into strips.
Between room temperature and it's liquid state, it will turn into an almost taffy consistency and stickiness! Cutting it into its final shape is difficult. You need to warm it enough that it can be cut without shattering, but not warm enough to stick to your instruments. The compromise that was made was to warm it enough to just barely cut it. This resulted in a bit of a mess that needed to be cleaned up.
The concrete base of the tool was now covered with a thin layer of pitch. This helped make sure that no particles of concrete would come loose and scratch the mirror. It also provided the base that the squares of pitch would stick to.
A small amount of turpentine was applied to the back of the squares to help them adhere to the tool.
At this point, the lap is almost done. The remaining corners will be fitted with properly cut pitch. Note the channels visible between the tiles. The bright light is from a heat lamp that was used to soften the squares so that they would deform slightly to the curved shape of the tool and make them stickier for good contact.
John and Jim are applying a bit of correction to the tiles. Some of them had a bubble hole or two in them that needed to be filled. The channel edges are where the polishing actually occurs. The holes could cause uneven polishing of the surface.
After the basic lap was finished, a bee's wax mold is used to impress a pattern onto the surface of the tool. This will speed up the polishing because it will form an edge at each ridge. The edges are where the polishing occurs most. (We used this only in the early stages of polishing as the small facets and rapid polishing are thought to produce small-scale ripple and roughness in the surface.)
Remember with the rough grinding that the grit acted like boulders that smashed their way along the glass surface. We went to finer and finer grit. Since we are after a surface with an accuracy measured in fractions of a micron, we cannot find a grit (or even powder) that would be fine enough for the original boulder approach. Rather, the pitch will be covered in polishing rouge and the rouge will be used to scrape the surface smooth. Some theories suggest that the heat from the constant rubbing and scraping will cause the glass to flow at the molecular level and have the material from the peaks fill the valleys on the surface.
Finally we are ready to start polishing...