Laser printed labels

Printing
--------

At the Herbarium of the Australian National Botanic Gardens (CBG) we
have been using herbarium specimen labels printed on archival quality
paper for many years, a decision based on the fact that since the
pigment contained iron and carbon, there would still be marks on the
paper in centuries to come, ie. the pigment was unlikely to fade. Inkjet
ink also contained carbon and was also considered acceptable, but at the
time the decision was made, laser printing was of better visual quality
and Postscript inkjet printers were not available.

Investigations into the suitability of this technology in the herbarium
and outside in the living collections on 'plastic papers' revealed that
laser printer and photocopy pigment was hygroscopic and when moist would
slowly flake off, in effect, rust.  With the relatively stable and low
humidity in temperate herbaria this may not be a problem, but in non
air-conditioned tropical herbaria it might be (but vanishing ink is the
least of your specimen maintenance problems in such environments).  The
problem was found to be significant for outside labels and some form of
water impervious coating was advised or a different printing technology
such as thermal transfer that did not contain iron and melted the
pigment into/onto the medium.

 [ On a related issue we are looking for a supply of stock of UV-stable
   waterproof paper substitute for printing horticultural labels that
   will hold printing and last in full sun for at least 5 years.  Does
   anyone have any ideas?  Is anyone doing it already? ]

Specimen accession barcodes at CBG are printed by laser printer and are
included as part of the label.  Abrasion may be a consideration where
the physical contact of a barcode wand is involved.  The laser printed
barcode could withstand 200 passes (by which time I tired of the test)
of the wand without detectable deterioration of the barcode.  As it is
unlikely that a barcode will be scanned more than a dozen times a
century, I do not think abrasion is an issue here; the use of scanners
rather than wands could perhaps be recommended as a standard for
herbarium/museum use.

We also use laser printing to print label information, barcodes, etc,
directly onto heavy paper packets for mosses, liverworts, etc.  This is
quite efficient but the choice of paper stock is critical.  Some
archival papers had a short fibre length and would not fold into packets
without cracking, others had a particular finish that would not allow
the laser ink to bond strongly or completely.  That latter caused the
pigment to smear and rub off when two printed surfaces were rubbed
strongly together, although not to the extent that the words could not
be read.  As the packets were filed vertically without covering folders
and rubbed against each other as they were taken in and out of the
drawers, this was considered important.

Jim Croft
Herbarium CBG
Australian National Botanic Gardens
GPO Box 1777, Canberra, ACT 2601, Australia
+61-6-2509 490
fax: +61-6-2509 599

                                  ***
                  Conservation DistList Instance 6:39
                Distributed: Saturday, January 23, 1993
                        Message Id: cdl-6-39-001
                                  ***