Re: [ATM] Polishing staining

[Hugues.Laroche@ses-engineering.com]

Hello Mike, Doug and all, 

>My guess is that the mirror is simply not getting cleaned
>properly after polishing.
>
>> I'm doing my bi-annual ATM class here...and having a
>> problem I've seen once before that seems to be
>> inexplicable: Polishing plate glass 6" blanks on Gugolz 64
>> using CeO from Salem, several of the students get a thin
>> filmy coating on their mirros which seems to be removable
>> with acetone and hard, and I mean hard, rubbing 

Yes the mirror might not be cleaned properly. 

However I had recently a similar phenomenon polishing 
a borosilicate mirror with nano-trent (extremely thin CeO) 
on a machine. The mirror was clean beforehand, but had an 
opalescent film disposed on a zone afterwards. 
I did not try "really hard rubbing" but indeed nothing 
could wipe this film as if it was imprinted into the glass. 

I suspect it was the case and it was clearly visible 
in the Foucault test. The explanation, for me, is most likely that 
I let the wet go to far on the dry side (of the Force ;-). 
The only thing that made it go is much more machine polishing, 
2 hours before I could not detect any film anymore. 

Morality: don't get your polishing too far when it dries! 
It is anyway known to be avoided, but on a machine it can 
go quickly too far from the moment you notice the dryness and the 
moment you can stop and remove everything. 

Wonder if that would happen with something else than CeO? 

Hugues 


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