Has anyone tried Breathing Color Metallic?

Started Mar 22, 2013 | Questions thread
Hugowolf
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Re: Has anyone tried Breathing Color Metallic?
In reply to soloryb, Mar 24, 2013

soloryb wrote:

Hugowolf wrote:

<snip>

‘Optical brightening agent’ is an industry euphemism, they are in most cases actually florescent – they give off light at the UV end of the spectrum when light falls on them. If you look at the plot of either the RR paper or the Moab paper, you will see more than 100% reflectance at around the 440 nm mark. The paper is actually putting out light; it is fluorescing.

Sure coatings and UV/museum/conservation glass will slow the decay of the OBAs, but they do this by preventing light in that region of the spectrum from hitting the paper. And if they do this effectively, the brightening agents will no longer brighten as much, and the effect will be the same as if the OBAs had faded. You lose a lot of the reason for using a ‘bright’ white paper in the first place.

The more expensive spectrophotometers, used for creating paper/printer profiles, can measure without and with UV light (UV cut and non-UV cut). Specifically for this type of situation – UV emittance under UV blocking material.

Brian A

Thank you once more Brian. What you say about UV varnish and glass over a paper rich in these fluorescent OBA (FBA) chemicals makes complete sense. The process of fluorescence relies upon absorbing UV wavelength photons which then are re-radiated at wavelengths in the visible spectrum. So blocking the UV would obviously stop the fluorescence in the first place. Just wasn't thinking.

How about non-UV blocking coatings - if there are such things?

There are some coatings that make no claims about UV protection, so one would presume that they offer little or no protection from UV light. And there is regular framing glass and plexi. But then you wouldn't be protecting the other things that degrade with UV light, the paper and the inks themselves, you would be protecting from water damage, finger prints, dust, etc.

Brian A

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