OBAs and UV Glass/Acrylic

[hubell]

Am I correct that white highlight areas of a print made on a paper with optical brightening agents such as Canson Photographique Baryta will appear greenish yellow if you frame the print with a UV protective glass or acrylic?
Thanks.

[Schewe]

It shouldn't...putting a print with OBA's behind a UV absorbing glass or plastic should simply not engage the OBA's. The net result should be the base paper color showing through the glass/plastic. It shouldn't in my experience turn a color other than perhaps a bit duller and maybe a bit warmer.

[Ernst Dinkla]

There is a wide variety of UV blocking glass, acrylics, foils with very different optical effects on the paper white and print colors. If you put the glass on a Non-FBA white surface like Teflon, Tyvek you wil see the color of the glass itself. When put on FBA media you get that same color + a reduction of the brightness as less UV will get through to activate the FBAs and so less light is emitted from the paper in the blue range of the spectrum. The color shift and he brightness can drop considerably if the paper relies on the FBAs mainly for its white reflectance.

http://www.aardenburg-imaging.com/news.18.html

PDFs with spectral plots of UV filtered glass etc:
http://www.icn.nl/nl/search/global?query=UV+werend
UV-werende eigenschappen van verschillende typen glas, kunststof en folies voor museale doeleinden (276kb)
UV-werende filters voor museale doeleinden (133kb)


met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

[hubell]

This is the discussion that I recalled. I just recently framed a very large print on Canson Photographique Baryta with Tru Vue Museum Optium Acrylic, which has excellent reflection control and UV protection. However, the photograph has prominent white highlights, and when the photo was hung, the white highlights had a somewhat greenish yellow cast that I never saw when I made the test prints. (Same Solux lamps.) This seems consistent with what Mark McCormic-Goodhart is describing, or am I misunderstanding his comments?

   
Re: Canson Infinity Baryta Photographique? (or other OBA-free baryta paper?)
« Reply #8 on: May 12, 2011, 06:28:56 PM »
   ReplyReply
Quote from: JeffKohn on May 12, 2011, 02:51:27 PM
I've never seen a "cool" paper that didn't have OBA's in it. If you really want that, maybe consider the non-UV version of Museum Glass (I think it's called TruVue Anti-Reflection).

Ditto.. this other Tru Vue product with anti-reflection (AR) coating (not to be confused with "reflection control" products that use an etched surface to scatter light) is not a full UV-cut barrier. However, this glass and its "Optium Acrylic" counterpart (i.e., AR coating on standard acrylic versus Optium Museum Arylic which has an AR coating on OP3 full-UV cut acrylic) are the "sleepers" in the True Vue product lineup. They are somewhat less expensive than their Museum glass and acrylic counterparts, but they get little attention because most framers try to upsell the AR coatings on full UV-cut glazing material, ie. the so called "museum" quality glazing. Nevertheless, these variants of AR coated glazings are very important to modern digital media because they cut more UV than standard glass and even somewhat more than standard acrylic, but are still not full UV blockers. Hence, a high OBA content paper like EEF won't take quite as much of an "instant yellowing" hit as it does with Tru Vue Museum glass or Optium Museum acrylic. My advice would be to get some samples and compare paper color changes to standard acrylic which blocks more UV than ordinary glass, but not as as much as the "museum" stuff.  Think of these two other AR coated glazings as a decent compromise for UV cut versus UV transmission but with the attribute of lower front surface reflection and no loss of sharpness and contrast which is the common complaint with typical "reflection control" glazings. You will still see some decline in that ultra bright white appearance of EEF compared to framing under ordinary glass (which can impart a slight green tint) or "water white" glass (which is free of the impurities in the glass that cause the green tint). However, it won't be quite as much paper color change as the Museum glass which the OP tried.

I don't think even Tru Vue fully understands this "sweet spot" in its product lineup because the use of ultra high OBAs is a fairly recent development in photographic papers. Framers that recommend museum glazings are often unaware of an OBA containing paper's need for some UV in the illumination to achieve it's fluorescence benefit.  Moreover, traditional darkroom photographic papers with OBAs never got so "ultra blue-white" as we are seeing recently in the inkjet paper market, so for both reasons, these intermediate AR coated products don't get their just due attention in the picture framing community.

cheers,
Mark
http://www.aardenburg-imaging.com

[Ernst Dinkla]

This seems consistent with what Mark McCormic-Goodhart is describing, or am I misunderstanding his comments?

Trust your eyes I would say. That it is also described by Mark adds to that observation.

met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

[hubell]

Trust your eyes I would say. That it is also described by Mark adds to that observation.

met vriendelijke groeten, Ernst

New: Spectral plots of +250 inkjet papers:

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm

Apparently so, but this does add a whole other layer of proofing to get the colors right. Not only do I need to view the test prints under the same type of lighting as they will be displayed under, I need to keep some samples of the types of glazing I might use. It just would never have occurred to me to choose a glazing with LESS uv protection with certain inkjet papers.

[MHMG]

It just would never have occurred to me to choose a glazing with LESS uv protection with certain inkjet papers.

From end-user initiated research undertaken in recent years, we are all learning something new 

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
http://www.aardenburg-imaging.com/cgi-bin/mrk/_4899c2hvd19kb2NfbGlzdC80

Conservation framing experts are also going to need to refine their marketing message that currently states full UV-cut glazing is always "best practice".


cheers,
Mark

[AFairley]

I have been looking into this a little, from a practical framing perspective.  As previous posters have pointed out, the glazing itself will add a color cast to the print.  Last weekend I overlaid swatches of TruVue Museum Glass (anti-reflective coated, 99% UV filtering, TruVue AR Reflection Free glass (anti-reflection coating, 78% UV filtering), and glass from a cheap mass-produced 8x10 frame on a print made on Exhibition Fiber.  The Museum Glass added a brownish cast, the AR added a greenish cast, and the cheap glass added a greenish cast, but less than the AR (but the cheap glass was 2mm while the AR is 2.5mm).  All of the brights looked dimmer under all of the glass, but to about the same degree.  What I could not tell, because I didn't have a sample of known OBA-free paper was how much that effect is the result of the glass itself and how much is the result of UV blocking (I assume the plain glass blocks some UV, but do not know how much -- one web site said 25% blocking, the "International Ultraviolet Association" website said "Normal glass (as used in windows) is transparent to UV radiation up to a wavelength of about 330 nm (or UV-A light). The transparency is quite high so almost all UV-A light will pass through glass. Below 330 nm (UV-B and UV-C), almost 100% is block by normal glass".  I took some photos that I will post eventually. 

I personally prefer the color cast that the Museum Glass adds to that of the AR, but AR costs 3/4 as much as Musuem Glass, and is somewhat easier for me to cut because of the sizing.  TruVue also makes an non-convservation glass, UltraVue (anti-reflective coating, 65% UV blocking) which is "white water" glass, so I assume it imparts less of a color cast -- but it only wholesales in lite sizes that are too large to be practial for me, so that's not an option for me.

I am contining my investigations.  BTW, does anyone know if the Epson Hot Press is OBA free (I have a sheet of that lying around)?

[Sven W]

BTW, does anyone know if the Epson Hot Press is OBA free (I have a sheet of that lying around)?

Yes, if it's the Natural version. The Bright version has a "medium" content of OBA

/Sven

[Alan Goldhammer]

All of the brights looked dimmer under all of the glass, but to about the same degree.  What I could not tell, because I didn't have a sample of known OBA-free paper was how much that effect is the result of the glass itself and how much is the result of UV blocking (I assume the plain glass blocks some UV, but do not know how much -- one web site said 25% blocking, the "International Ultraviolet Association" website said "Normal glass (as used in windows) is transparent to UV radiation up to a wavelength of about 330 nm (or UV-A light). The transparency is quite high so almost all UV-A light will pass through glass. Below 330 nm (UV-B and UV-C), almost 100% is block by normal glass".  I took some photos that I will post eventually. 

For indoor applications you don't need to worry about UV-B (and UV-C is negligible in any event other than a laboratory condition where it can be produced) since normal light sources do not produce much if any of it.  The only issue with OBAs is that they require light in the wavelength range of 330-350 or so which will cause the agent to fluoresce at the 430-440nm range.  It is this wavelength of light that is blocked by UV-protecting glass/plexi and if you are relying on papers with OBAs you cannot use such glazing.  As you noted normal glass blocks UV-B rays which are not necessary for fluorescence but can cause print damage because of the energy of the light waves.  However, you really would have to have the print exposed to direct sunlight for this to happen.

[datro]

I have been looking into this a little, from a practical framing perspective.  As previous posters have pointed out, the glazing itself will add a color cast to the print.  Last weekend I overlaid swatches of TruVue Museum Glass (anti-reflective coated, 99% UV filtering, TruVue AR Reflection Free glass (anti-reflection coating, 78% UV filtering), and glass from a cheap mass-produced 8x10 frame on a print made on Exhibition Fiber.... 

This is exactly the kind of data I'm trying to find regarding glazing for my B&W prints.  In addition to the three samples you tested, I'd also be really interested in how the UltraVue (which uses water white glass) and Optium Acrylic (not the Optium Museum Acrylic) compare in terms of adding color cast.  Anybody have any comments on these two?

Dave