Can you tell UV from Non-UV acrylic?

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smantecon

smantecon

CGF, Certified Grumble Framer
Joined
Jul 2, 2004
Posts
142
Loc
Dana Point, California
Hello -

I had a customer come in today who had 4 vintage posters framed from a BB (who outsources the framing) with UV acrylic.
She got a call from the employee who ordered the acrylic saying she got regular acrylic, not UV. She did pay for the UV. The employee felt they had to let her know, but doesn't want to lose their job.

Her question; is there any way to tell the two apart? I don't know the answer. She wants to make sure before she confronts this place. Actually, I would really like to know as well to.

Thank you.
 
Right, Edie.

A UV "black light" would illuminate through ordinary acrylic or glass, but the light magically disappears through UV filtering galzing.
 
Jim, That is not quite true:

Take a white towel and lay the acrylic and the acrylic of known type on it to compare with. Darken the room and shine a black light on it. Check this link. This is typical.

http://home.att.net/~jriegle/uvacrylic.jpg

Glass is on the left. It blocks hardly anything. Standard acrylic is in the center. I looks like 60%, but is blocking well over 80% (illumination is a non linear function). It is Acrylite FF. The piece on the right is Acrylite OP-3 blocking around 97%. Even standard acrylic is far better at blocking UV then standard glass.
 
The reason that the paper towel shows up so dramatically, in the absence of a UV filter,
is the florescence of the optical brighteners
used in its manufacture. Laundry products also
use such brighteners to make our clothes "whiter
than white" and thus white clothes glow in
black lighting.

Hugh
 
To those of you who know, if you shined a black light onto the framed package would the "whites" in the print/image show purple?

Would this be a way to check UV-ness without opening the frame up?
 
Originally posted by JohnR:
Jim, That is not quite true...
[/QUOTE

JohnR, your testing conditions are different than mine. When you demonstrate with a white sheet of paper and a small black light in a hotel meeting room with the lights on, the violet light clearly shows through ordinary glazing, but it does not show through UV filtering glazing.

Technically, there certainly must be a slight passage of violet light because only 98% of the (approximately) 250nm-380nm UV range is getting through, but in a bright room it can't be seen.

We're all on the same wavelength, though...
Click to expand...
 
If interested, here are typical curves for filtering effects of glazing.
http://home.att.net/~jriegle/graph.jpg
If the art is covered with regular acrylic, It is safe to say it is pretty well protected from the effects of UV. For the best protection, however, the UV filtering grades of glass or plexi is the way to go.

Bob, The Black light trick won't be a good test because different materials and papers fluoresce at differing intensities. Without a control group to compare with there is no way to be sure.

One way to test would be to use the second surface reflection. By this, I mean sending the light into the glazing so it bounces off the back surface and analyzing the spectra that emerges. It would require advanced equipment.

Scott, if the customer agrees, open one frame and use your new black light to compare with a sample piece of UF-3/OP-3 and regular plexi.
John
 
John's curves are similar to some I've seen, but they differ somewhat from the latest curves provided by Tru Vue & Cyro. Their curves for UV-filtering glass and acrylic run slightly to the right of the 400 nm line.

Bob's black light trick would probably be good enough to serve the purpose. Nearly all of the violet light would be filtered out by a 98% UV-filtering glazing, so the remaining 2% would show through very little, if at all. On the other hand, if the glazing has no UV filter, the roughly 60% of violet light transmitted might easily be seen on white items in the frame. It's a sort of all-or-nothing test.

The only "gray area" I can think of in Bob's test would be for anti-reflective "AR" glass, which filters about 78% of UV light, even though it does not have a purposeful UV filter and is not considered a preservative glazing. So, about 22% of the violet light would show through, but in a bright room, that might not be visible on some white surfaces in a frame.
 
Jim,
Cyro's OP-3 does have a more aggressive UV filter. It is a superior product to the typical stuff.

I disagree that the UV light through frame will be good enough test. My argument is that different materials fluoresce differently. Many white papers without optical brighteners won't glow much or at all. I have some white core mats that the core glows brightly under the UV light while some other white core does not. Same with prints. Without a “known” to compare with, the test is inconclusive.
 
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