White gloves

The study which Doug Nishimura referred to in his April 22 message
was performed in 1992 by Rudiger Krall from Germany and the late Dr.
Klaus Hendriks.  The work involved examining the literature to
determine the composition of sweat which is the major component of
fingerprints. Subsequently, artificial sweat solutions were made and
applied to a range of photographic materials from salted paper
prints to contemporary silver gelatin prints.  The samples were aged
at 60 degrees C and 75% RH for up to 30 days.  It was determined
that sodium chloride was the most active ingredient in sweat that
can lead to staining.  To verify this polished cold rolled steel
plates were used in experiments as Doug described.  The incubation
was at room conditions of 23 degree C and 50% RH for 14 days.
Several people were tested and some (like Doug) produced significant
rusting of the plates even before the 14 day period had elapsed.
The ability to cause rusting varies with the amount of sodium
chloride content in the sweat and it differs from individual to
individual.  It is dependent on factors such as rate and duration of
sweating, skin and environmental temperature, activity, salt intake
and even the time of year (the concentration of sodium chloride can
be twice as high in the winter as in the summer time).

Some useful references on the corrosion of metal by sweat are given
below:

    Burton, J.L. et al.  Metal Corrosion by Chloride in Sweat.
    British Journal of Dermatology Vol. 95, July to December 1976,
    pages 417-422.

    Buckley, W.R. and Lewis, C. E.  The Ruster in Industry.  Journal
    of Occupational Medicine. January 1960.

Joe Iraci
Canadian Conservation Institute
1030 Innes Road
Ottawa K1A 0C8
Canada
613-941-4991

                                  ***
                  Conservation DistList Instance 10:93
                  Distributed: Friday, April 25, 1997
                       Message Id: cdl-10-93-001
                                  ***