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I have just fine ground my first mirror. An F4 4.25 inch. Seemed to work reasonably well except for one very faint wiggly scratch. The earlier worse scratch ground out with aluminium oxide so I suppose I need to try another round.
I am wondering how much mineral oil or other material to temper my black pitch with for the polish lap. It has been used once but is too hard. I tried a few drops of mineral oil, less brittle but the penetrometer test only gave me a mm with 500g after 30 minutes at 19 degrees. I think I need 2.5mm.
Any advice welcome.
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