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Subject: Invisible inks

Invisible inks

From: Walter Henry <whenry>
Date: Friday, April 12, 1991
The following item appeared in sci.chem and is reposted here
without the knowledge or consent of the author.

    Article 3493 of sci.chem:
    From: ee5391aa [at] triton__unm__edu (Duke McMullan n5gax)
    Newsgroups: sci.chem
    Subject: Re: Invisible in normal light but fluorescent in UV?
    Date: 3 Apr 91
    Organization: University of New Mexico, Albuquerque

    In article <1991Apr1.093047.16106 [at] agate__berkeley__edu>
    mkent [at] dewey__soe__berkeley__edu (Marty Kent) asks about
    ultraviolet-fluorescent "invisible" inks.

    There's this outfit up in Washington State that sells books of the
    sort which make far-left liberals shiver in mortal fear and
    far-right conservatives salivate like Dr. Pavlov's dogs.  They are:

      Loompanics Unlimited
          P.O. Box 1197
    Port Townsend,  WA 98368

    Their current catalog lists _The_Secret_Science_of_Covert_Inks_ by
    Samuel Rubin (ISBN 0-915179-44-X), at twelve bucks ninety-five.

    There is a chapter on ultraviolet inks, from which I'll provide a
    few excerpts.  Rubin goes into some detail on different types of UV
    lamps, but isn't clear on which types work best with which inks.

    Dissolving quinine sulfate in a small amount of water to which a few
    drops of sulfuric acid have been added gives an ink that dries to an
    invisible-in-sunlight state which shows up blue under UV.  (Note
    also his precise, quantitative formulations.  ;^)

    Dissolve aspirin in water.  Instant blue UV ink.

    Pee in your pen.  Instant invisible ink. (So sayeth the book.)

    Now, a disclaimer:  I haven't tested _any_ of these.  All sound
    capable of gunking up your pen, but should be fairly easy to
    un-gunk.  That last one may smell a little funny, too.

    Nearly any "invisible" ink will be visible (though not necessarily
    easily so) on some types of paper.  "Your mileage may vary."

    I must add that, in my experience, using UV inks for
    clear-conscienced "annotating" of books is a completely novel


                  Conservation DistList Instance 4:54
                  Distributed: Friday, April 12, 1991
                        Message Id: cdl-4-54-006
Received on Friday, 12 April, 1991

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