There is a slate museum in Granville ny and Evergreen Slate Co nearby
518-642-2530 they may have information.
-----Original Message-----
From: Christopher Tavener <[log in to unmask]>
To: [log in to unmask]
<[log in to unmask]>
Date: Friday, February 26, 1999 11:35 AM
Subject: Re: A clean slate


>You may be looking at gypsum stains formed by calcite in the slate in
>reaction with water.  Such stains are an indication that the slate is
>beginning to break down, since the molecule of gypsum are larger then the
>calcite molecules and promote delamination. I guess you should deterimine
>whether you are looking at gypsum first before thinking about cleaning
these
>slate.
>Christopher Tavener
>ctavener @eypae.com
>
>-----Original Message-----
>From: Robert Buckle [mailto:[log in to unmask]]
>Sent: Friday, February 26, 1999 12:01 AM
>To: [log in to unmask]
>Subject: A clean slate
>
>
>I am looking for info on cleaning slate. Slate is being removed from a
>collapsed building. It is to be reused on  an adjacent building. It has
>some staining - white which may be a salt. The roof is near the ocean. The
>slate appear to be in good condition other than some staining. A chemical
>cleaner was recommend but I think this may not be required.  From local
>sources it appears the slate was installed in the 40s (second roof of a
>1907 wood frame builing...poorly constructed. Slate is attached with
>galvanized roofing nails.
>