Gum photosensitivity?

Hi All,
I've been spending way too much time this morning looking for something
that I can't find, and thought maybe it would ring a bell with someone.

Sometime back (maybe 1-2 years?) there was a discussion about gum being
photosensitive all by itself. I didn't pay it much attention at the
time, frankly because I thought it was nonsense, but recently I've come
across this assertion (in a book about the chemistry of chromium) "Many
colloids such as albumen and gelatin can be insolubulized by ultraviolet
light."

I suspect that what they really meant is that colloids can be
insolubulized by ultraviolet light in the presence of dichromate, and
they inadvertently omitted the crucial phrase. But just to be sure, I
spread some pigmented gum on a piece of paper and set it out in direct
sun for 3 hours and then put it in water, and of course it dissolved
totally in a few seconds; in other words no insolubulization whatever.

But I'm still troubled by the vague memory of this past discussion. What
I don't remember clearly is whether the person who brought it up just
read it somewhere and was asking if there was anything to it, or whether
the person actually claimed to have done it herself-- to have
exposed gum to light and got an image from it. (Funny how the memory
works; I can't remember the person's name, but I do think it was a
woman, and I think her name was a short name staring with M. I could be
clear wrong about that, but that's what I'm remembering.) Anyway I've
searched the archives with relevant keywords, and not brought it up, and
I don't have time to go through the whole archives sorting each month by
author and looking for a short name starting with M.

So if anyone can point me to the post, I'd be grateful. And if the
person herself is still here and can tell me anything about this, I'd be
ten times grateful. If she read it somewhere, then I'm inclined to not
give it much credence, given how much misinformation and straight out
nonsense is written about gum. But if she actually saw this with her own
eyes, then I want to talk to her.
Katharine Thayer
Received on Mon Apr 26 13:15:17 2004