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Fading After Using Museum Optium Acrylic

Bob Doyle

SPFG, Supreme Picture Framing God
Not a bad guess on my part. Was DenGlas 30%? I recall being shocked that it was less protection and three times the price of regular glass.


MGF, Master Grumble Framer
I use a similar box primarily as an eye catcher at the design counter for showing clarity and non reflective qualities. Though I haven't really included the entire light spectrum in my talking points, maybe I should. Most if not all of my up-sells to Museum glass are about reduced reflection and clarity, and the price differences between premium clear to conservation clear are so nominal that I rarely find the need to use premium. But having concise talking points around what 99% UV protection actually does relative to the entire package is probably worth having in my hip pocket. I guess I should dust off the cobwebs on some of those grey cells.
Ah, consider this about Museum Glass (plus any other optically coated low reflection glasses like Artglass etc) and Optium acrylic products.
They let more visible light into the art, by reflecting typically less that 1% visible light, while normal glass reflects about 8% visible light.
This is how we can see the detail of the framed art / item much clearer with the coated anti reflective products.

But by allowing about 7% more visible light into the art, items like the art work in the OP could have actually been affected a lot faster if the 'better' glass / acrylic was used (and it wasn't in this case anyway).

According to Wikipedia, UV is 100-400 nm. So, if a glazing protects against the 280-380 nm range, it's really only protecting against 33.3% of UV light.

Before someone "reminds" us that the most damaging part of light is 280-380 nm, so what? Isn't that exactly what this thread is about? That UV glass does not stop fading because light in the 280-380 nm range is not the only thing that causes fading.
See below re 'PRD'.

The wavelengths from 380 to 400 nanometers go from invisible to visible, and the visible wavelengths from 400 to 430 nm are partially blocked, which affects the color of the image.

View attachment 21833
There're a couple of points that dictate the UV frequency to block, and how different levels are / are not of consequence.
There are a quite a lot of UV light ranges, some overlapping, but the 3 main types of UV light we are looking at here are :
UVc - 100nm - 280nm. This is excluded by the earth's atmosphere.
UVb - 280nm - 315nm. Cannot pass through window glass.
UVa - 315nm - 400nm. Can pass through window glass, not affected by the atmosphere, present all day / everyday, makes up 5% of the suns total radiation !! (The one we have to block.)

The big question of what to block lies with how these frequencies damage in relation to each other.

There was once a REALLY good chart on the Optivex Filters website, about Probable Relative Damage (PRD), but this is no longer at the link I have referenced in my notes.
The closest I can find is a similar type of chart from the "Encyclopedia of Library and Information Science: Volume 7" PRD, . . . see screen shot attached of this page below.
Note - millimicrons and nm are the same value, just the PRD figures are scaled a little differently in the chart linked above and screen shot, and my notes from Optivex just below.

A shame the original info is no longer online, as it displays the different UV levels and relative damage very simply, in the simple numbers, but here it is copied from my notes :

'Probable Relative Damage' can be assigned to different wavelengths of light.
UV light at 300nm = ~ 7 PRD
UV light at 380nm = ~ 1 PRD
Visible light at 500nm = ~ 0.03 PRD

So it showed that blocking above 380nm was not worth the interference to the visible light range, and protection was more or less not really needed due to the lower PRD factors over 380nm.
It also showed the massively diminished risk of visible light levels, but we all know just how that CAN fade cheap mats, certain colours, etc.

Incidentally, it's not that hard to coat glasses to block UV, we have done it many times using nano particles specially mixed and suspended in a clear 2 pack paint base with special additives to coat glass.
We coat the inside of our convex glasses where needed, and anything like old original (flat) wavy glass being reframed for original art restorations, so the original glass can be used and protect a restored piece of art.
Our coating blocks 85% UVa, but in the 320nm to 390nm range.

The tricky part is applying it without any defects !!
We have it pretty well down pat now when coating to a satisfactory level.
I take my hat off to all the present and past producers of UV clear glasses, as it must be a great headache to keep the quality up in such end product.

Terry Scidmore CPF

MGF, Master Grumble Framer
Just as many others have pointed out, all light can be damaging. Tim Padfield has written extensively for the conservation community about how visible light in the near UV range is still damaging to those colors that are damaged by visible light. One paper in the Journal of the Illuminating Engineering illustrated this point with a test of color fading. 50% of the fading in the test colors occurred with no UV exposure and was related to visible light. Hence, the location of the art on display is just as important as the glazing. A TV article written by Judith Walsh counsels hanging artwork in low light locations - such as a hallway, or a bedroom with light filtering drapes, or draping the art with cloths to limit exposure to "unregulated light", such as one might find in your average home or office environment. She also recommends using UV glazing as an additional protection, both in the museum environment where type and strength of light is controlled, and in the home and office environment where it is not.


SGF, Supreme Grumble Framer
I was clearing out my storage and found the display model that Tru Vue used to give out showing the fading caused by not using True Guard. It's pretty old so it probably has nothing to do with their current policies but at least some of you won't think you've lost your minds. They did make these at one time.



Rob Markoff

PFG, Picture Framing God
Thanks for posting that Ed. That must be really old (or I am and do not remember it :) ). I don't even remember TruGuard as a product!

Bob Doyle

SPFG, Supreme Picture Framing God
Not that old Rob, I have been framing since 2001 and that sure looks familiar to me! Thanks Ed, I thought I might have been losing my memory, glad to know that I wasn't.

Found a website that listed it as their favorite glass option, in 2004 and another that in their source code showed the page had been written in 1999.

I think that could be the glass that I put in a customer's frame that came back fro rematting (they had gotten a new sofa to match I think :))

The glass was decidedly green, and i remember when picking out mats with the really finicky customers that I would place a piece of glass on the mat design to be sure that the color shift would not influence their decision!
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SGF, Supreme Grumble Framer
I think I got that in '97 or '98. So to young people it's really old and to older people it was just yesterday.



MGF, Master Grumble Framer
I was clearing out my storage and found the display model that Tru Vue used to give out showing the fading caused by not using True Guard. It's pretty old so it probably has nothing to do with their current policies but at least some of you won't think you've lost your minds. They did make these at one time.

I have seen a few TV split faded print POS displays like that over the years here in Australia, though not that particular print.
At the time, was led to believe that the prints were copied and printed from an original faded sample, to present the imitation fading . . . makes sense, as such a mass distributed display could not really be produced economically (or repetitively) with real time fading.

Personally, I feel that was a poor print to do this with, better to have a more even split of detail, like this real time faded print I used for a demo piece (distributing Guardian Inspiration).

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