A simple but effective method for monitoring cracks is done with
overlapping glass slides (microscope slides) across the crack, the
distal end of each one attached to the wall with an epoxy resin .  An
initial scratch at the point where the slides overlap gives you the
starting point and over time new scratches, with dates as well if
desired, will give the required monitoring advice.  Make sure the
plaster is sound at the points of attachment.  Or you can demonstrate
the cracks are moving by attaching a single slide across the crack,
glueing at both ends, which will break apart under the stress of
movement.

Ron Vanderwal
> ----------
> From:         [log in to unmask][SMTP:[log in to unmask]]
> Reply To:     Museum discussion list
> Sent:         Thursday, 25 June 1998 7:28 AM
> To:   [log in to unmask]
> Subject:      plaster monitoring
>
> I work in a historic house museum that is beginning to show large
> cracks in
> the plaster.  Some of these have developed due to settling, others,
> due to
> poeople touching the walls ("look at the hole in the wall...").  Does
> any one
> have any idea of a product that will help monitor the growth of these
> cracks.
>  I once saw a product at the Octagon House in Washington, DC- they
> looked
> like "bandaide" that attached to the wall and was calibrated.  Any
> other
> ideas.  I thought it would also be a great way to educate our visitors
> about
> historic preservation/restoration in a site like ours, so it does not
> bother
> me to have something show.
>
> You can email me at [log in to unmask]
>
> Thanks for any ideas.
>
> Elizabeth Walker
> Curator
> Molly Brown House Museum
>
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