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Subject: Calcium carbonate crystallites

Calcium carbonate crystallites

From: Gabriella Borg Bonaci <pedin>
Date: Wednesday, March 22, 2006
I am currently working on a large print dated 1765. The print was
heavily varnished about 20 years ago and was lined onto a linen
support. I have looked at the stratigraphy of the four layers (linen
support, adhesive, paper, varnish) using SEM after treating the
print in ethanol and water. I have observed calcium carbonate
crystallites in the void region (where varnish and adhesive may have
been detached while grinding the sample) between the paper and the
linen support and again in the void region in the varnish layer.

Does anyone know where the source of this calcium carbonate may have
originated?  Can this be a loading method used during paper
manufacture that was adopted prior to 1765? or could this simply be
contamination on exposure to dust and the environment?

Gabriella Borg Bonaci

                  Conservation DistList Instance 19:47
                 Distributed: Wednesday, March 29, 2006
                       Message Id: cdl-19-47-021
Received on Wednesday, 22 March, 2006

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