Baryta budget alternative

Started 8 months ago | Discussions thread
mike earussi Veteran Member • Posts: 9,298
Re: OBAs and UV filtration

Mark McCormick wrote:

NAwlins Contrarian wrote:

...I think we need to point out here that if you print on a paper containing a substantial amount of OBAs and then display the print behind glass that substantially filters out UV light, then the paper will not look the same once displayed as it looked out of the printer. AFAIK there is no way to have it both ways: the paper is designed to look a certain way by being exposed to UV light and then using that to affect the visible appearance. If you prevent it from getting that exposure, then it won't look like it was designed to look.

+1.

So, two facts to keep in mind. First, In the absence of UV radiation falling on the print surface, blue wavelength photons still have enough energy to cause print fading, albeit not as potent as the UV energy in natural daylight by a factor of 2-4x.

Second, OBAs work by absorbing UV radiation (the peak absorption value for OBAs is about 370 nm). This energy excites the colorless OBA dyes such that they fluoresce strongly by then further emitting blue wavelength light. This fluorescence is what the viewer observes to make the paper appear brighter and more blue-white in appearance. Take away the UV radiation (by framing under UV blocking glazings or by adding UV absorbing overcoats or by using LED or other lighting that doesn't emit UV radiation) and you shut down the "bright white" fluorescence effect in papers containing OBAs.

You'd be surprised how many professional framers don't know about OBAs and thus try to sell you more expensive UV blocking glazings (museum glass, OP3 plexiglass, and the like) without any awareness as to whether the print has OBA content or not. The visual appearance of a print with any appreciable amount of OBAs will be immediately impacted and appear to look more yellowish and duller in overall appearance. Some folks may not notice. Discerning viewers will indeed notice the result of this immediate loss in fluorescence.

Mark, maybe you've hit upon the strategy of how OBAs actually work. Their real purpose is to help sell the print while it's displayed in a plastic bag that doesn't block UV light. Then once it's framed the customer has forgotten how the print looked before framing and is happy with the framed result.

Very clever really.

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