Chinese ink tablets

I am currently surveying the condition of a varied collection of
organic material.  I have come across a set of Chinese ink tablets
(blocks of solid ink with finely moulded designs and embossed
lettering), which I think are probably made of carbon black.  Some
of them have a whitish bloom on the surface.  Does anyone know what
causes this and whether it is likely to be damaging in the long
term?

Flora Nuttgens
Department of Eastern Art
Ashmolean Museum, Oxford
England


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                  Conservation DistList Instance 16:7
                   Distributed: Friday, July 19, 2002
                        Message Id: cdl-16-7-014
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