Herbarium

Lea Dauwalder <lea.dauwalder [at] hkb__bfh__ch> writes

>... I would like to collect
>experiences of conservators having already dealt with the problem of
>preserving herbal material, especially herbaria in book form. So if
>you have experience with the following problems, I would be very
>grateful to read about the solutions you chose:
>
>    Dry cleaning the paper sheets supporting fragile specimens
>
>    Consolidation of loose plants: how and with which kind of
>    adhesive?
>
>    Pest control and treatment (also the handling of objects which
>    may have been treated in the past with harmful pesticides)
>
>    Storage

This is rather a minefield as I am sure you are aware!  I have no
experience of dealing with herbarium material beyond the later-18th
century but will put in what I know and have experienced in case
there are no other replies.

For dry-cleaning paper I use Groom Stick, providing that the paper
is sufficiently robust and hasn't been at all weakened by fungal
attack.  Otherwise I use Draft Clean carefully, bearing in mind that
it is micro-abrading the paper surface. Smoke sponges can also be
used in this context and may be effective.

For consolidation and adhesion I still use neutral pH PVA diluted to
50% with deionised water.  This will wet the specimen slightly so it
would be advisable to start with a fragment first and only use
sufficient adhesive to provide enough tack.  I have not tried
paraloid B72 as this might seal the tissue.

For pest control I use anoxic treatment using barrier film and
oxygen scavengers and am always aware that arsenic salts may be
present in older herbaria as pest preventers.  Just be aware of that
and be careful not to inhale dust (extraction bench and at least a
dust mask) and normal hygiene procedures (nitrile gloves, hand
washing etc.).

Storage: a pest and security-secure herbarium cabinet should be
fine. Ensure that the herbarium books are stored inside some other
acid-free container.  I have seen paper conservators making such
containers from acid free card.

All materials are available from most conservation suppliers but
especially Preservation Equipment Ltd.

Simon Moore MIScT, FLS, ACR,
Conservator of Natural Sciences


                                  ***
                  Conservation DistList Instance 25:20
                Distributed: Wednesday, October 19, 2011
                       Message Id: cdl-25-20-006
                                  ***