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Old 02-07-2018, 09:36 PM
Wavytone
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Wavytone is offline
 
Join Date: Jul 2008
Location: Killara, Sydney
Posts: 4,147
Billy if in doubt you can grade the grit yourself using water. The procedure is described briefly in one of A.G. Ingalls ATM books, you should own these; if not BUY A SET on ebay.

Personally I wouldn't trust the grit from a source that wasn't a reputable one with a firm connection to ATM - lapidary supplies definitely do NOT qualify.

The test will be when you think you've ground out the pits of a previous grade, inspect with a loupe. If you see scratches, the grit ain't what its supposed to be.

Cerium oxide is for polishing - not grinding - and is an alternative for black-rouge. In my mirror-grinding days I tried both. Cerium oxide polished faster but produced a rougher surface. On small surfaces (secondaries and lenses) it was so aggressive it isn't a good idea as the figure will be terrible and uncontrollable. IMHO not suitable for mirrors under 30cm.

Rouge is slower to polish, but produced a much smoother surface and better figure and ultimately a far better result - with patience and a lot of elbow grease. If you have the patience I would use rouge - not cerium oxide.

I continue to have doubts about your experience... anyone who has ground a few mirrors before would know these basic things.

Last edited by Wavytone; 02-07-2018 at 09:49 PM.
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