Acer V <siddim01@xxxxxxxxxxxxxxx> moved upon the face of the 'Net and spake
thusly:
> <snipped table w/ data>
>
> So what is it that causes fade or color shift exactly? What's it about
> bright light? (museums don't want flash photos either;
Many dyes and pigments are complex organic molecules. Light and heat
break them down.
> read "faked" aged
> documents are made by exposing to HID lamp)
The yellowing of old paper is usually caused by lignin (a component of
wood) breaking down into simpler stuff. Lignin is *supposed* to be
removed during modern papermaking processes, but cheap paper (eg
newsprint) still contains it. That's why cotton-based boards are
preferred for photographic mounting use rather than wood-based ones.
cjb.
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