Sil Horwitz (silh@iag.net)
Tue, 30 Mar 1999 15:53:30 -0500
At 99/03/30 01:08 PM -0800, jewelia wrote:
>environmental concerns...optical brightener is a term used for additives
>sometimes used to whiten a bleached pulp (usually) more and, perhaps moreso,
>to increase the opacity of the paper...the usual optical brightner is
>titanium dioxide -- a pigment, not a dye. titanium dioxide is quite stable
>and is a common pigment used for white "color" paints and other mediums.
I think what Nze is concerned about is the organic optical brighteners, which
are, indeed, dyes used extensively. While these dyes are colorless, they have
the capability of converting light in the UV range to white light capable of
being seen by the human eye. These optical brighteners (dyes) are used in
almost all clothes washing compounds, which is why clothes washed in most
popular compounds glow when seen under a UV lamp. This same test can be applied
to paper: if it glows under UV, it contains a dye-based optical brightener. I
am not personally familiar with anything bad about them (color printing papers
include them) and though I haven't done any testing, they should be neutral.
They absorb UV which might be a good thing in alternative printing methods! One
cautionary note: these materials are water soluble and too long an immersion
can leach them out of whatever media contain them.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net
Visit http://www.psa-photo.org/
Personal page: http://www.iag.net/~silh/
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