Fax paper

Karen,

Your question is a bit ambiguous: are you interested in faxes or in
thermofax, which is not a facsimile transmission process but a copying
process?  On the off chance that you actually are interested in the
latter:

    "Thermo-Fax is a trade name of the 3M Company for a thermographic
    copying process.... In this process, the sensitized material
    consists of a thin sheet of paper containing certain chemical
    compounds which, when subjected to heat of an appropriate
    temperature, form colored substances. When a sheet of this material
    is placed in contact with a document and exposed to infrared (heat)
    radiation, the infrared rays pass through the non-infrared absorbing
    sensitized material to the document, where they are  absorbed by the
    metallic or carbon content of the text. The text is thus actually
    heated up to a temperature high enough to convert the chemical
    compounds in the sensitized layer to coloured substances to form a
    visible image." [Hawken, William R. _Copying Methods Manual_. LTP
    Publications, No. 11, Library Technology Program, American Library
    Association.  Chicago, 1966]

    "Thermofax [note spelling variant -wh] is a single step, dry method
    of producing copies.... The material used in this process is a thin,
    heat-sensitive paper, which is not sensitive to normal light and can
    therefore be operated in any room.... To produce a copy, this paper
    is placed in contact with the original and exposed to infra-read
    light.... The white parts of the original reflect most of the heat
    but the black parts absorb and re-radiate the heat, which penetrates
    through to the heat-sensitive coating of the paper and so produces a
    positive copy. [Verry, citation on request]

    "The process was refined and later marketed in 1950 by 3M Company
    under the name Thermo-Fax.... The process used heat-sensitive paper.
    Exposure to infra-red radiation was by the reflex method. The black
    portions of the original reflected the heat radiation and darkened
    the corresponding portions of the paper in contact with the
    original." [Nadeau, Luis.  _Encyclopedia of Printing, Photographic,
    and Photomechanical Processes_., 2 vols.  Atelier Luis Nadeau. New
    Brunswick, 1989.]

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                   Conservation DistList Instance 7:1
                  Distributed: Wednesday, June 9, 1993
                        Message Id: cdl-7-1-005
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