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Subject: Laser pointers

Laser pointers

From: Katy Untch <kuntch>
Date: Tuesday, December 7, 1999
This response was sent to me as a response to my inquiry about laser
pointers.  The author has asked me to share it with this
distribution list.

    In 1992, I coordinated the content of a book on light entitled
    L'eclairage dans les institutions museales.  We looked at
    several issues, but it was before the introduction of laser
    pointers as we know them today.   In 1994, I was asked by a
    curator from a big museum in Quebec city if they were acceptable
    for museum use. Although I suspected they could be low in
    degradation  potential, I had not proof of that.  So I decide to
    conduct a small empirical study on the subject on a variety of
    materials.  This study is still unpublished, but I wish to
    present my results if time can permit.

    A laser pointer was held on a stand, and the samples were put on
    a rotating disc to simulate the random effect of the light
    illuminating the object.   Samples tested were: Blue wool
    samples, from 1 to 8, silk, cotton, linen, cardboard, balsa,
    ivory, leather, Ethafoam, an epoxy adhesive, an acrylic, PVA,
    B-72, and a sample of Erythrosine B. The disc was rotating at a
    speed of about 100 turn per minute, and the exposure was limited
    to one hour a day, for fifty days.  To make sure ambient light
    was not interfering with the results, the samples were located
    in a black colored container, with very little illumination
    inside.  After more than fifty hours of testing, nothing was
    visually detectable on the samples; any interference would have
    shown in the form of a trace,  originating from the path of the
    laser light on the samples.  I then decided to put my samples in
    accelerated ageing, in an oven at 50 celsius, for fifty hours,
    again with no visual or perceptible alteration.

    All in all, I think that for a limited exposure they could be
    acceptable, but even if this experience suggest that they seem
    to be  harmless, I have reluctance to recommend its
    generalisation in the museology community.   As Marie Svoboda
    wrote to you, the lasers used are of the IIIA class, and thus
    potentially dangerous for the human eye.  Caution must be
    exercised in this respect.  The wavelength  of the laser I
    tested is centered around 760 nm, with a dispersion of plus or
    minus 5, so we are talking about a low energy emission here
    (contrarily to a U.V. emission, for example).

    Hope this is useful.

    Andre Bergeron,
    Centre de conservation du Quebec,
    1825 Semple, Quebec city, G1N 4B7,

Katharine Untch
Conservator of Objects
Virginia Museum of Fine Arts

                  Conservation DistList Instance 13:34
                 Distributed: Sunday, December 12, 1999
                       Message Id: cdl-13-34-006
Received on Tuesday, 7 December, 1999

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