From: Wayde Allen (wallen@boulder.nist.gov)
Date: 02/03/00-11:54:13 AM Z
On Thu, 3 Feb 2000, Richard Morris wrote:
> On cleaning the glass, if you want to use the original, beware that some
> of this glass is very "soft" and easily fractures. I actually cleaned the
> glass of a Lerebours dag - now many thousands of dollars worth of image!! -
> but it had to be reused and remounted. The underside of the glass appeared
> to have a mercury deposit but very careful rubbing with a moist cloth using
> a bit of vim did the trick. But my heart was in my boots as I did it! It
> had to be done as the image was completly obscured by the dirty glass.
I think one really should consider replacing the cover glass rather than
just cleaning it. The problem is that the glass ages and softens. Then
it begins to flake, droping very small pieces of glass down onto the dag.
plate itself. I don't believe that cleaning and replacing the existing
glass stops this process.
NIST recently redesigned and built a new box for holding the United
States Charters of Freedom (Declaration of Independance, Bill of Rights,
etc.) due primarily to the deterioration of the cover glass. See
http://www.nist.gov/public_affairs/Charter/charters_of_freedom_project.htm
- Wayde
(wallen@boulder.nist.gov)
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