[ATM] Removing a chrome(?) coating layer

[Jim Burrows]

At 2007-12-22 18:08 +0100, Guntram Lampert wrote:

>A few days ago, I tried to remove a mirror coating by polishing it off
>since I intended to do some figuring anyway.
>
>A first layer came off pretty quickly, followed by a second one that
>left a dark grey residue on the lap. No doubt this was the aluminium.
>But now I am left with a metallic layer that I suspect is chromium.
>
>Now, I can´t get rid of this first layer. Treating it with diluted
>hydrochloric acid, no result. Added ferrous chloride solution, nothing.

Probably what happened is the lap got an 
equivalent "crust" - this often happens during 
ordinary polishing - glass particles get embedded 
in the lap so the polishing compound no longer 
does its work.  Give the lap a wire brushing to 
expose the pitch, recoat with rouge or CeO 
(whichever you're using), warm press for contact, 
and hit it again.  You'll have to do this same 
process sometimes between figuring spells.

         -- Jim Burrows
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