Re: ATM How to remove coating from secondary?

["Bill Cotten" <billsas@worldnet.att.net>]

----- Original Message -----
From: "The Silent Observer" <silent1@ix.netcom.com>
> It may still have -- steel wool is a good deal softer than Pyrex, so you
> may be able to remove any remaining coating and find the glass
> essentially undamaged.  I'd recommend giving the primary the same
> treatment as you give the secondary to remove the coating, and then
> assess the surface condition before making a decision to refigure or
> repolish.

The primary is clearly toast! Deep gouges, swirls of severe scratches in the
glass etc. It is already being reground as I write this. Believe me, if
there was any hope of saving it we would have done so.

> Nitric acid won't touch ordinary aluminum -- it reinforces the oxide
> coating that protects aluminum, instead of cutting through it.

Thanks. We did not know that. We keep the nitric around for silvering
mirrors.

> Either add a little table salt to the hydrochloric (making a weak version
of
> aqua regia) or, better, get some muriatic acid (sold for cleaning
> concrete); that's another name for hydrochloric, and it will remove the
> aluminum in a jiffy without harming the glass in any way.  I'm assuming
> here that you can handle acids safely, based on the fact that you had
> nitric acid handy.

I'll try the muriatic first since I'm a concrete finisher and always have
some on hand. Our ATM meeting was on the other side of town from my place so
muriatic was not handy.

Thanks,
Bill