Microbiologic deterioration of photographs

Microbiologic deterioration of photographs: results of one study

A few months ago I sent a message to the Cons DistList and to
several people that I found the contact here. I received some
answers with fresh views and references about my doubts regarding
microbiologic deterioration of photographs. The best way I found to
say thanks  is to present the major conclusions I achieved in my
investigation project:

I. Identification of microorganisms isolated from gelatine emulsion
photographs

    In about 56 positive samples taken from B&W and cromogenic color
    photographs (mainly negatives and slides) belonging to 3
    collections from Lisbon institutions, the major Genus were:

        37% Penicillium
        24% Aspergillus
        10% Cladosporium
        19% several Fungus
        10% several Bacteria

    Generally, these results have a correlation with the few similar
    studies referred in bibliography about C&R of photographs and
    archival materials.

II. Microbiologic contamination statistic study about Horacio Novaes
collection from Caloust Gulbenkian Art Archive

    In about 29351 negatives and slides:

    *   The major results were that 20% of this collection was
        contaminated,

    *   Nitrated base negatives had the highest percentage--39% (the
        oldest photograph materials in the collection)

    *   B&W  and cromogenic color have the practically the same
        percentage of contamination, about 20%. However, there are
        some important issues for the interpretation of these
        result: 1) the statistic universe of B&W materials (25280)
        is much higher than the color species (4071), so the B&W
        results is much more reliable.2) the photographer H.Novaes
        mainly used B&W materials since the 30's to the 70's, and
        cromogenic color materials since 70's to the 80's.
        Therefore, the color materials have less time of
        inappropriate storing conditions, and presented the same
        degree of contamination.

    *   It is considered that the best way to interpret these
        results is by comparing them with other similar studies.

III. Induced contamination experiences with gelatine emulsion
photographs

    The goal was to test the existence of biosusceptibility
    differences between color and B&W photographs

    *   The experiences showed that the B&W photograph materials had
        a distinct growth of fungi between highlight areas (without
        silver particles) and lowlight areas (high concentration of
        silver particles). The white areas in most of the cases,
        presented a more intense development when compared to black
        areas.

    *   The experiences with color cromogenic photograph materials
        showed no difference between highlights (without dyes) and
        lowlights (high concentration of dyes)

The main objective that initiated the statistic study (I) and the
        induced contamination study (III), was based on the
        existence of hypothesis of the bigger biosusceptibility of
        color materials. Several professionals that deal with
        collections defend that, at least in plastic base supports
        (negatives and slides), color materials are more
        contaminated than the B&W ones. These studies do not prove
        this hypothesis but, however, the results do not discard it.
        Further investigation is needed in order to a better
        understanding this matter.

I would be pleased to answer any queries related to this subject
Thank you again for your help.

Miguel Lourenco


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                  Conservation DistList Instance 17:57
                  Distributed: Tuesday, March 2, 2004
                       Message Id: cdl-17-57-003
                                  ***