Thanks, Mark.
I'm still not so sure about the term "natural white." Certainly it would be helpful to have an industry-standard term or phrase to describe papers that contain no OBA's. Alas, I don't think any such phrase reliably exists. I just picked up boxes of two of my most-used, OBA-free papers (Canson Platine Fibre Rag and Epson Hot Press Natural). Neither have the phrase 'natural white' displayed anywhere. Not to be overly pedantic... it's certainly not going to be an issue for the typical visitor to a forum such as this; but to the extent that you're trying to educate your clientele, I'm not sure I would depend upon that phrase. At the very least it's not comprehensive.
Regardless, again, you are to be congratulated for trying to look out for them...
Hi guys,
yes, I slightly mis spoke when I replied to Mark in our earlier private conversation. The most common hint that media is OBA-free is the vendor's use of the word "natural" not "natural white" in the product name, or the vendor will actually boast that the product is OBA-free somewhere in other description verbage. A common hint that the product does contain OBAs is when the term "bright" is used somewhere in the product name or product description, but none of this advice is a hard and fast rule by any means.
It's really easy for the enduser to confirm the presence of OBAs with a low cost blacklight. So, when in doubt, buy a sample pack, shine a blackight on the media, and see how strongly it glows. You can use a known OBA-free product like Epson hot (or cold press) "natural" and compare to product with low amount (HN photo rag) or high (Epson premium presentation matte paper) to strengthen your confidence in the black light technique. Note: if you buy an LED blacklight, there are two common varieties, one emitting with a peak output at 365 nm, and others emitting around 395nm. The latter produce a more significant output also in the visible blue region, so this Blacklight test is harder to interpret with the 395nm LED output because even the OBA-free papers start to reflect their radiation (rather than emit) in the blue wavelengths. With practice, one can still use either for the test, but I much prefer the 365 nm variety which match the OBA UV absorption peak very closely, and OBA-free papers will appear with virtually no bluish glow using the 365nm LED devices. Google "UV 365nm LED flashlight", for example, to find these portable UV lamps.
Other ways to confirm OBAs: 1) if you have a spectrophotometer like a Colormunki or Eye-one Pro (used without a UV cut filter, the b* value for the media color will become negative. The best OBA-free papers turn in b* values of 0, 1, or 2, but never negative values. High OBA content papers will measure -5 to -10 or more! 2) check out Ernst's wonderful Spectrum Viz tool (
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm ), or 3) you can check the lightfade database at Aardenburg Imaging & Archives. Each AaI&A record lists OBA fluorescence and whether it's none (i.e. OBA-free paper), low, medium, or high. Ernst's spectral plot database is more complete with respect to OBA content information than the Aardenburg database because I only measure samples that also go through the full light fade test protocol. That's been a big undertaking, so I can't check out as many samples as I'd like to.
I hope to have the Aardenburg website back on line in the next day or so. The redesign and deployment of the new site on a different hosting platform has been a big project for me.
cheers,
Mark
http://www.aardenburg-imaging.com