RE: [ATM] Lemon Juice and Optics

["Thomas" <tomjan@ozemail.com.au>]

How about because caustic (high pH) solusions can and do etch glass.
Acids in general (excluding HF) have little or no effect on glass....

Clear skies,
Thomas Janstrom
http://www.tjanstrom.com
http://www.norsewines.com.au
"Your nobody untill you've been ignored by your seventh cranio-facial
nerve."


-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf
Of Woodchuck
Sent: Monday, 10 May 2004 7:35 AM
To: The Amateur Telescope Makers List
Subject: Re: [ATM] Lemon Juice and Optics


On Sun, 9 May 2004 jroweapp@postoffice.swbell.net wrote:

> Dear Richard;
> I agree!!  When companies that manufacture and or, distribute glass 
> polishing compounds post the ideal pH values for the use of their 
> polishing compounds, there must be a reason. I can site Salem 
> Distributing for one. If you have bought goods from them and received 
> a catalog, they post optimum working pH values for their polishing 
> compounds. I doubt their information is meant to misleed or win trivia

> contests. They try to provide information so their clients can produce

> the optimum result. I would suggest acetic acid, (white vinegar) and 
> pH papers or a decent pH meter to arrive at the advised pH. Regards
> Jeffrey Rowe

Better yet would be a buffer solution at the proper pH.  The challenge
would be to find one that keeps its pH as it evaporates, and does not
leave any nasty-scratchy salts as it does evaporate in use.  Vinegar has
this nice property of evaporating completely, but it's not a buffer. I
suspect that vinegar ought to be adequate, though.  It's probably a
range that is wanted.

Question now on the table, *why* an acidic pH? Possibilities:
	*) formation of sodium silicate or borates from the glass being
ground?
	*) control of flocculation of the grinding slurry, i.e. breaking
up clumps of abrasive/polishing compound and other substances?
	*) control of staining from certain compounds? (on certain
glasses?)
	*) needed for certain "exotic" glasses to prevent or encourage
something? (If so, what?)
	*) something obscure, like hydration of the glass surface?

Dave

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