Nothing that lets light through is going to 
protect any piece of artwork completely. So after 
that, you can only aim for a degree of protection
-- and UV protective glass DOES block UV light!

I don't have fancy meters, and won't put any cels 
in the light as tests. . . But I have one UV 
sensative toy. I opened a window to direct sun. 
In direct sun, the toy changed colors immediately.
Took it into the shade to let it come back to 
normal, then showed it the sun through a piece of 
regular glass. It changed, albeit the change was 
a *tad* slower than in the direct sun. Took it 
into the shade to bring it to normal once more, 
then showed it the sun through UV protective 
glass. Nothing. Left it there for hours. Nothing. 
Not a hint of a color change. The sun was starting
to go away when I lifted the UV protective glass, 
and the toy changed color.

So if the glass doesn't block anything, what kept 
the toy from changing?

It is also important to note that the prints ARE 
different from cels. Different media = different 
conservation methods. You don't preserve a piece 
of needlework the same way you preserve a granite 
statue or a glass negative or an oil painting. In 
some cases there are many similarities, but the 
different media never react wholly identically to 
each other when presented with any one potentially
damaging element.

And I'm glad to see I wasn't the only one who 
noted the reds/blues issue in the experiment. 
Even just *within* the more red picture, look and 
see what did the purple fade to? It faded to 
BLUE. Meaning that (comparing different colors of 
the *same* type of ink to itself) the red element 
in the color is what was leeched out first, and 
the blue element was stronger. (For those behind 
on their art studies: purple = red + blue.)

I do believe (just by virtue of it's COMPLETE 
lack of change, even in the red by the horizon) 
that the bluer one had to have been made with 
more colorfast inks -- or it could be the paper 
on which the inks were printed (there are a 
number of factors that can come into play here)
-- but it's still a bad comparison. A better 
comparison would have been to find a restrike 
print of the exact same image. (Or barring that, 
a restrike print that uses equvalent amounts of 
like colors.)

But all that said. . . I do think this thread is 
on topic. Our cels might react differently, but 
this shows something about the range of the 
glass's protection.

And the image of the women really was very pretty.
I wonder how many collectors of those prints are 
thinking: "Why did he wreck *THAT* one!?!?" ^_^;;

Many Sharp Smiles,
--Drac