Artsorb

Gali Beiner <gali.beiner [at] pitt-rivers-museum__oxford__ac__uk>
writes

>In one of our display cases we keep several trays containing Artsorb
>as a buffer for maintaining a RH level around 50% as stable as
>possible. The trays have been in the case for the last 5 years. They
>are made of metal (aluminium, as far as I can tell) and the Artsorb
>in them is the white bead type. When checked recently for refreshing
>the buffer material, I found that all trays had a considerable layer
>of Artsorb stuck at the bottom--stuck so hard that it was
>practically impossible to scrape off without very great effort.
>
>As far as I know, Artsorb is a silica gel. It apparently contains
>lithium chloride, so it may be corrosive to metal. Does that explain
>why it got stuck to our aluminium trays? Has anyone else had a
>similar experience with Artsorb getting stuck?

I have observed a similar reaction between Artsorb beads and
aluminium metal. In my case, the beads were stored in soft aluminium
trays and left untouched in a sealed container for 1-2 years. After
that period, the bottoms of the trays were completely corroded, thus
when I tried to lift the aluminium trays, all the beads ran away
through the bottom.

Therefore any contact between the Artsorb beads and metal objects
must be avoided. Moreover, the reaction of LiCl with volatile
organic acids to form HCl vapours (subsequently reacting with
metal/glass objects) cannot be excluded and should be tested. Such
reaction previously occurred in atmospheres containing NaCl solution
(to maintain a low RH) and organic acid vapours.

Laurianne Robinet
Equipe archeomateriaux
Laboratoire Pierre Sue
Commissariat a l'energie atomique
Saclay, France


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                  Conservation DistList Instance 21:7
                   Distributed: Monday, May 28, 2007
                        Message Id: cdl-21-7-006
                                  ***