Hill's Space

12" Mirror Making: Pitch Lap Problems

 |  1 min  |  122 words
Looking top down on a stack. From top to bottom: mirror (currently a piece of glass, but it'll become a mirror), cerium oxide polishing compound (white), black pitch tool. The white in the center shows there's a slight gap between the pitch and the mirror.
A tub of hot water is used as a weight to press the pitch to the mirror so the pitch takes on the mirror's shape
After some pressing while immersed in a hot water bath to ensure the pitch flows, the black pitch is touching the mirror in the center as well. Good contact achieved!
After some polishing action, the entire pitch lap surface looks evenly worn down! Good.

My pitch lap polishing tool wasn’t making good contact with the center of my mirror. I can tell because I’m just beginning polishing and so I can see that the mirror’s outside is more reflective than the inside. Also, the tool looks unevenly worn.

I tried heating up the tool using a tub of hot water so the pitch would flow and then pressing the tool against the mirror some more (pictured) but it seems to have only helped slightly. In the end I placed both pitch lap and mirror in a tub of hot water and pressed while underwater - and that heat seems to have finally let the pitch flow and fully copy the mirror shape across the entire surface.

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