Fine Art Photo Black Papers Without OBAs

[mike_botelho]

I've been doing a lot of reading and will soon be ordering samples of a number of fine art papers, and could really use a little help when it comes to deciding what I want to try.  I'm interested in good fine art papers, the type which are made for printing with photo black ink, that also have no OBAs.  Highest gamut and d-max are desirable (under the circumstance of having no optical brighteners), and I'm more partial to glossier and smoother offerings.

All in all, there are so many options, choosing a few papers to try can be a little daunting, but, since I want to avoid OBAs, that does automatically narrow the field.  So far, I've determined that Crane Museo Silver Rag and Hahnemuhle Photo Rag Pearl don't have OBAs, and I read Michael's comment that Ilford Gold Fibre Silk has 'essentially' no OBAs (though I'm not really sure what 'essentially' means in this instance).  Also, I haven't managed to determine whether the other new barytas, the Hahnemuhle Fine Art Baryta and the Harmon Gloss FB AI, have OBAs or not.  (Wow, this is almost like learning a new language.)

Anyway, any suggestions, info, advice, or descriptions would be greatly appreciated.  I haven't yet found any source that summarizes all the paper choices and their characteristics.  I'll keep on looking and reading, but if any such source of information exists, I very much appreciate a link.

Thanks for any potential help navigating through all the options and specs.

Kind Regards,

Mike

[rdonson]

If you contact Jim Doyle or any of his staff at Shades of Paper I'm sure they be happy to help you with your selection.

[Geoff Wittig]

Near as I can tell, most of the spiffy new "baryta" papers use OBA's to give that maximum "punch" to the image. Epson's "traditional photo", Hahnemuhle's fine art baryta and Harman's FB AL gloss use a lot of OBA's. It's a trade off. If you look at a high contrast black & white print on one of the OBA-loaded baryta papers side-by-side with the same image printed on something like Hahnemuhle photo rag pearl, the print with OBA's will have more snap. On the other hand, you'll lose a lot of that snap if it's framed behind UV blocking glass, and no one knows how quickly those OBA's may fade.

I spend a lot of time fine-tuning my image files to produce exactly the color balance and contrast that serves the photograph best. I don't want that subtle effort wasted when the color shifts a few years later as the OBA's lose their ability to flouresce.

[MHMG]

All in all, there are so many options, choosing a few papers to try can be a little daunting, but, since I want to avoid OBAs, that does automatically narrow the field.  So far, I've determined that Crane Museo Silver Rag and Hahnemuhle Photo Rag Pearl don't have OBAs, and I read Michael's comment that Ilford Gold Fibre Silk has 'essentially' no OBAs (though I'm not really sure what 'essentially' means in this instance).  Also, I haven't managed to determine whether the other new barytas, the Hahnemuhle Fine Art Baryta and the Harmon Gloss FB AI, have OBAs or not.  (Wow, this is almost like learning a new language.)

[{POST_SNAPBACK}][/a]

As it turns out, I have samples of all the papers you mentioned in my lab as of last week. Here's a run down on OBA content based on Black light evaluation.

Crane Museo Silver Rag - none

Hahnemuhle Photo Rag Pearl ( I assume you mean Fineart Pearl) - Moderate level OBA concentration in ink receptor coating, moderate in paper base

Hahnemuhle Photo Rag (in case you meant this product, but it is a matte fineart paper, doesn't emulate photo fiber base)- none in ink receptor coating, high in paper base,

Hahnemuhle Fineart Baryta - moderately high in ink receptor coating and in paper base

Ilford Gold Fiber Silk -  none in ink receptor coating, high level in paper base, low in anti curl layer (but may be "show thru" from base).

Harmon AI Gloss - low in ink receptor coating, moderate in paper base, low in anti curl layer

Bottom line: a "yes" or "no" answer to the question "does it contain OBAs" is not easy. Manufacturers put different concentration levels in different coating layers and concentration and location influence the extent of the OBA "problem". This subject is of great interest to me because of the current concerns about OBA presence and image permanence. My light fade studies so far have not statistically shown a difference between fade resistance of different manufacturers' OBAs. Presumably, the chemistry is very similar.  What the studies have shown shown clearly is that high levels in the ink receptor coatings from any of these manufacuturers are highly likely to contribute to early stage paper white changes in light fade testing. OBA fluorescence loss occurring significantly in as little as 10 megalux-hours ( equals 5 years on display at industry standard 450lux/12 hour per day average estimated display light levels). Also, note that the level of colorimetric (or densitometric) change attributable to loss of OBA fluorescence is typically below the "failure point" criterion for paper white yellowing in industry light fade testing criteria so it is generally unaccounted for in "display life" figures, yet it is definitely noticeable to discriminating printmakers and print collectors.

What all of this means is that papers containing no OBAs are free of early stage paper "yellowing" but may in fact show some very subtle light bleaching that "whitens" them. Papers that have OBAs in paper base but not in ink receptor coating are likely to show just noticeable but not easily noticeable visual changes due to OBA "burnout", whereas papers with moderate to high levels in the ink receptor coating are very likely to show noticeable loss of "cool bright white appearance" in relatively few years on display. That said, if initial paper color isn't all that important  to you (ie. you don't mind "bright white" or "natural" paper white color appearance) and paper surface texture is important to you, then anyone of these papers may become your preferred choice. Note also, that if you frame under UV filtered glazing, you will lose that "super bright white appearance from high OBA content immediately (because it is the UV content at  approximately 370 nm wavelength that triggers the fluorescence).

Other factors with these papers, especially with pigmented inkjet systems, are level of bronzing and differential gloss. In my tests, these factors also significantly differentiate these papers, and are more likely to affect your final buying decision, so it isn't a simple go-no go proposition on OBA content or any of these parameters for that matter. You really need to try a sample pack or two, and check them out. For example, while I appreciate Michael Reichmann's preference for IGF (it certainly wins on price), I find it has more bronzing and differential gloss on my Canon ipF5000 than other papers you mentioned. Thus, while very attractive to me in price, it is hard for me to say I "prefer" IGF because some of the other papers you mentioned perform better in initial overall IQ on my ipF5000. Wish I could tell you there was a clear cut winner, but ultimately it is very much a matter of personal taste.

I hope this explanation helps,

Best regards,

Mark McCormick
[a href=\"http://www.aardenburg-imaging.com]http://www.aardenburg-imaging.com[/url]

[neil snape]

I have tested a new photo base Baryta with no OBA in either the coating nor base, and is a cotton base too. I will post a review in the end of August, and of course send a news report of it to Michael.
In the review I measured the spectral characeter of some Baryta and RC type papers.

If what Mark is saying about OBA is certain, then as I have been saying and Henry Wilhelm , Mark, is if possible your ideal appearance if within your expectations best to avoid OBA.
The harder paoint is how to use 0 parts OBA between batch and maintain paper whiteness. Using OBA in the surface like certain Epson papers do is not a great idea for maximum permanence.

It is however fine for more temporary display.

That has always been my beef. As photographers turned printers at the same time , we need to not only educate ourselves in so many new fields, but make decisions based on this newly acquired knowledge at print time. That is where the biggest area of concern has not been clear. Thanks to Mark, some information is coming out, yet we are all hungry for more. In the meantime you will see many posts from people including mine trying to help spread the word, but those words are are like the holes in Swiss cheese.

[neil snape]

Mike, try these links

http://www.pusztaiphoto.com/articles/print...ms/default.shtm
http://www.pusztaiphoto.com/articles/print...s/webchart.shtm
http://www.outbackprint.com/papers/paper_d...tory/essay.html
http://www.outbackphoto.com/printinginsigh...i042/essay.html

hope trhis helps

George
[a href=\"index.php?act=findpost&pid=210701\"][{POST_SNAPBACK}][/a]

Please note in Laszlo's graphs the light source is also part of the reflection qualities. Not that it makes a difference to the visible light for which an i1 is designed to report, but nevertheless a factor in the graph itself.

In UWE's report he says the permanence with OBA in media is falsely condemned. Well that is wrong. Just because the OBA will degrade leaving the appearance to come back to something of a non brightened paper, the permanence IS questionable. Henry told me the OBAs could have catalyst or other chemical side effects. Splotchy degradation, uneven coloration other optical derivatives all go along with this degradation. What, when,  and how exactly is beyond me and obviously a challenge for the best of researchers. It is one though that
Mark is addressing. Maybe we are again reaching into areas that the marketing side will disallow or reject any claims as it will surely change the way we make media purchasing decisions.

[Ernst Dinkla]

I hope this explanation helps,

Best regards,

Mark McCormick
http://www.aardenburg-imaging.com
[{POST_SNAPBACK}][/a]

Mark,

This is a nice summary after the discussion on the Wide Inkjet Printers list but what I miss is what RC papers and RC paper with OBA (most of them) show on the issues you mention. While their behavior to light will not be different the RC barriers usually protect against gas fading and it wouldn't surprise me that even in your tests ozone or plain oxygen has an influence on the OBA dyes. There's also my observation in the discussion that the use of barite goes along with the use of more OBA while TiO2 used in RC and other inkjet papers could do without or have less OBA as straight TiO2 is a better whitener than barite. There's a TiO2 substitution going on in the general whitener's market where like in all goods pricing is an issue.

Let me phrase it in another way for the RC aspect: tests by Wilhelm and Image Engineering show interesting fade resistant results on the RC papers when ozone comes into play, for both dye and pigment inks. As OBAs are mainly effective in unframed conditions where no glass can cut out UV beyond 370 Nm the effect of ozone becomes the more important factor too when the OBA effect is intended. While the OBAs are not effective framed behind UV cutting glass and less effective behind normal glass they may alter less in that condition too as ozone influence is low and degradation by light (UV) is low too. Compared to framed behind glass in the print exposed bare the RC barriers at least reduce gas fading in general and probably the influence of humidity in light fading. What remains is the degradation of the RC polymer composite itself (in combination with TiO2 whitener) and its bond to the paper. There has been a long R&D period between the introduction of RC paper for analogue photography and its use now in inkjet printing. I see rough numbers like 75 years quoted for RC paper as its degrading time but I wonder how recent these numbers are and in what way tested and if that is for the analogue or the inkjet type.

Inkjet printing is a modern technology still highly in development and where there are good reasons to be conservative and use older known substrates to achieve a long life there should also be an open mind about equal or better alternatives that could be more recently developed. In painting the acrylic medium introduced in the 1950's and further developed since showed to be at least equivalent to older artist's media.


Ernst Dinkla

Try: [a href=\"http://groups.yahoo.com/group/Wide_Inkjet_Printers/]http://groups.yahoo.com/group/Wide_Inkjet_Printers/[/url]

[Geoff Wittig]

Hahnemuhle Photo Rag Pearl ( I assume you mean Fineart Pearl) - Moderate level OBA concentration in ink receptor coating, moderate in paper base

Mark McCormick
http://www.aardenburg-imaging.com
[a href=\"index.php?act=findpost&pid=210740\"][{POST_SNAPBACK}][/a]

Nope. Hahnemuhle's photo rag pearl and fine art pearl are two completely different papers. They do have a similar surface texture, but photo rag pearl has no OBA's and uses the classic photo rag cotton base. Fine art pearl instead uses (I think) an alpha-cellulose base and substantial amounts of OBA's.

[MHMG]

Compared to framed behind glass in the print exposed bare the RC barriers at least reduce gas fading in general and probably the influence of humidity in light fading. What remains is the degradation of the RC polymer composite itself (in combination with TiO2 whitener) and its bond to the paper. There has been a long R&D period between the introduction of RC paper for analogue photography and its use now in inkjet printing. I see rough numbers like 75 years quoted for RC paper as its degrading time but I wonder how recent these numbers are and in what way tested and if that is for the analogue or the inkjet type.

Inkjet printing is a modern technology still highly in development and where there are good reasons to be conservative and use older known substrates to achieve a long life there should also be an open mind about equal or better alternatives that could be more recently developed. In painting the acrylic medium introduced in the 1950's and further developed since showed to be at least equivalent to older artist's media.
Ernst Dinkla

[a href=\"index.php?act=findpost&pid=210775\"][{POST_SNAPBACK}][/a]

The development of RC papers in the late 1960's-1970s has definite parallels to what happened recently with the dye-microporous/ozone debacle. The engineering and marketing efforts that promoted the rapid processing features of RC over traditional fiber base prints were blindsided by   unanticipated field failures where end-users were reporting light-induced silver tarnishing in B&W RC and then later on, serious cracking of the polyethylene layers which affected both B&W and color RC. These problems had not been picked up in the standard laboratory accelerated aging tests that industry relied on at the time to bring these products to market. We have had a similar situation with the gas fading issues for inkjet printing. In hindsight, these unanticipated weak links in the new technologies were logical outgrowths of the properties of the new material components. Years of industry research brought the RC discoloration/PE layer cracking problems under better control (by incorporation of anti-oxidants, etc) but PE layer cracking still remains a weak link for RC/TiO2 papers.  The best estimates today, as Ernst has noted, call for 75-100 years of display time before light induced PE layer cracking occurs , but these predictions are admittedly problematic. In fact, after more than 20 years of effort by an ANSI/ISO committee to create an aging test protocol for B&W RC, the technology essentially dissappeared from the mainstream photography market before the committee could agree on a method to reliably induce the cracking problem routinely in an accelerated test condition.

RC paper isn't the only material with susceptibility to cracking.  I have seen evidence of ink receptor layer cracking numerous times even on brand new materials.  For example, I just made some prints on the new Fuji 400-DL machine. This new "dry lab" inkjet technology is beginning to replace wet chemistry equipment in the photofinishing market. I understand that both Ritz Camera and Walmart are now phasing out RA4 print process compatible equipment in favor of this new drylab system, so 400DL prints are going to become very common consumer photos in the US photofinishing market. When I picked up the prints, I noticed that the ink receptor coating on the current formulation of the 400DL supplied paper is so brittle that the cutting blade itself induces crack propagation in the coating layer at the leading or possibly trailing edge of the paper as it gets cut. Also, the technicians handling the prints were causing additional creases and cracks just by taking the prints off the tray on the machine (no doubt they will get more instructions soon on how to handle the prints). This inkjet technology is a classic resin coated paper/dye/microporous system.  So why is the microporous image layer (not the RC layer) so brittle? My guess is it is related to mordant chemistry to better anchor the dyes and reduce humidity related image bleed and color drift which can plague dye-based inkjet prints.  To summarize, it is risky to treat any inkjet paper technologies as a general class with respect to image permanence because there are so many formulation variations even within each category. We just have to keep testing the products on their individual merits!

Ernst, the RC paper advantage in accelerated Ozone tests is at least partially though perhaps not entirely a consequence of the test method itself. Prints are usually free hanging in Ozone chambers which gives the ozone greater opportunity to diffuse towards the colorants from both sides of the print. Naturally, the PE layers help protect the colorants from penetration through the back side more than does fiber paper base in this type of test condition.  Whether the RC paper  advantage in test will play out in real life remains to be seen. Typically, the verso of the print is usually up against another surface like a wall or a table, and this situation curtails penetration from the back side.

I find the issue of image permanence for unprotected prints somewhat of an oxymoron. While gas fading of inkjet prints is clearly a huge product liability when it occurs in days or months, the notion that anyone can keep any unglazed, unvarnished, or otherwise uncovered work of art on paper or canvas lying about for 50 or 100 years without serious consequence to image quality is absurd. The work will be hugely affected by everyday dirt and grime, physical cracking and delamination caused mainly by seasonal humidity cycling, and mechanical damage caused by careless handling.  IMHO, the ability of art conservators to successfully clean the surfaces of today's uncoated inkjet prints in the future without causing more harm than good will be the subject of decades of new conservation related research, and the results will likely be very hit and miss.

Sorry about the long rambling post. Hopefully, people will find a kernel or two of useful news in it.

[MHMG]

Nope. Hahnemuhle's photo rag pearl and fine art pearl are two completely different papers. They do have a similar surface texture, but photo rag pearl has no OBA's and uses the classic photo rag cotton base. Fine art pearl instead uses (I think) an alpha-cellulose base and substantial amounts of OBA's.
[a href=\"index.php?act=findpost&pid=210855\"][{POST_SNAPBACK}][/a]

Hard to keep up with all the new papers! I will try to track some down.

[neil snape]

Nope. Hahnemuhle's photo rag pearl and fine art pearl are two completely different papers. They do have a similar surface texture, but photo rag pearl has no OBA's and uses the classic photo rag cotton base. Fine art pearl instead uses (I think) an alpha-cellulose base and substantial amounts of OBA's.
[a href=\"index.php?act=findpost&pid=210855\"][{POST_SNAPBACK}][/a]

That's correct.  The naming is confusing all of us already. It's not about to get better either....

[neil snape]

Interesting post Mark.

What other gaseous chemicals are known to be problematic for inkjet and or photographic prints other than ozone?

If I remember right the Epson 2000 pigment prints were changing colours depending on their proximity to pollution like LA. I can imagine that here in Paris it would be similar. It wasn't just ozone, so what was it?

[Ernst Dinkla]

Interesting post Mark.

What other gaseous chemicals are known to be problematic for inkjet and or photographic prints other than ozone?

If I remember right the Epson 2000 pigment prints were changing colours depending on their proximity to pollution like LA. I can imagine that here in Paris it would be similar. It wasn't just ozone, so what was it?
[{POST_SNAPBACK}][/a]

Nitrogen and sulphur oxides are other known sources for fade trouble.

What I recall of the orange plague, gas fading of the 879-1270-1290 dye (also used in the 10000, 9600-7600 dye models) that surprised both Epson and Wilhelm, was that the first reports came from coastal areas like LA that had higher ozone levels.

Was there also an Epson 2000 pigment issue?  The Archival pigment in that model scored high in fade tests at that time but lacked in gamut, showed high metamerism and low Dmax.


Ernst Dinkla

Try: [a href=\"http://groups.yahoo.com/group/Wide_Inkjet_Printers/]http://groups.yahoo.com/group/Wide_Inkjet_Printers/[/url]

[MHMG]

Interesting post Mark.

What other gaseous chemicals are known to be problematic for inkjet and or photographic prints other than ozone?

If I remember right the Epson 2000 pigment prints were changing colours depending on their proximity to pollution like LA. I can imagine that here in Paris it would be similar. It wasn't just ozone, so what was it?
[a href=\"index.php?act=findpost&pid=210877\"][{POST_SNAPBACK}][/a]

Neil, I'm not aware of any color change issues with 2000P prints other than the horrible color constancy (metameric failure) issues with this first attempt by Epson at a pigmented inkjet printer. I purchased a 2000P with great expectations but quit printing on it immediately because the color balance was so badly affected by illuminant conditions. I will never forget the moment it dawned on me that the one trade show image I had seen which influenced my 2000P purchasing decision had been very skillfully chosen to minimize the effect (marketing people are so creative!).  I do still own the printer because it is historically important despite my intense personal dislike of the prints it produces.

As Ernst has noted in his most recent post, I think you are recalling the "LA smog" annecdotes associated with the 870/1270 dye based printers that were released, if I recall correctly, in 1999, just ahead of the 2000P. It was the 1270 dye set, released with great fanfare as a new and improved lightfast ink set, which created all the commotion when the dreaded orange shift started showing up in owner's prints literally within days after printing! The problem was eventually identified as gas fading not related to light exposure at all, and further laboratory tests more or less concluded that ozone is the big culprit. Canon did do some mixed gas studies, and showed evidence at a technical conference I attended that NO3 and SO2 can also contribute to color fading (even in traditional chromogenic color papers), but in samples I saw, the resulting damage to the chromogenic color print sample was nothing like I've ever seen in real world field experience. In fact chromogenic color prints had never been tested for gas fading sensitivity because no field failures were ever identified that would have caused experts concern about the possibility of gas fading. That is another reason why the ozone/microporous experience caught so many experts by surprise.  The mixed gas studies, while interesting, remain unconfirmed by real world evidence that there is much of a mixed gas problem. Ozone is the big culprit and essentially for microporous inkjet not traditional color photos that use "swellable" gelatin binders.

Lastly, I've witnessed severe discoloration on some cast coated papers caused by solvent off-gassing or residue from various packaging tape adhesives.  Very bright yellow deposits can form as well as other stronger brownish-gray stains on the surface of some fine art papers that have come close to these adhesives (as for example, when they are used to tape shut a kraft paper wrap that houses a batch of the inkjet paper. The top sheet in proximately to the taped kraft paper will get affected and the stains don't show up sometimes for weeks or months after the exposure.  The stains are often light bleachable, but not always 100%, and anyway, that's no consolation to the mortified print buyers who watch the stains appear.  Note the advice, for example, given by Hahnemuhle, in their fine art paper instruction sheets..."prints should only be packaged in polyethylene composite plastic sheets and no adhesive tape should be used for sealing. Components of adhesive tapes containing solvents can diffuse through the packaging!" All of that said, I haven't seen these adhesive related problems with PH neutral acrylic adhesive tapes such as those recommended for conservation matting and cold mounting.

[mike_botelho]

I've been out all day today taking photographs, so I was very interested to come home and see all of the interesting discussion in this thread.  I'd like to thank everyone for the very interesting information.  I'm not sure I've made much progress in finding new papers without OBAs, but the topic is extremely important and fascinating nonetheless.

Obviously, this is a very evolutionary area of study, and its great that some are doing work to help sort things out.  In regard to those that are investigating various issues with specific papers, are there any summaries of findings that are available on the web.  I find it very interesting to read about the issues that challenge longevity in inkjet prints, but I am also curious in regard to specific issues with individual papers.

Nonetheless, this thread is definitely inducing me to think more and learn more about those factors that affect an inkjet print's well being, both in regard to the properties of individual substrates and also in regard to a variety of environmental factors.

I'll definitely be ordering some samples of Crane Museo Silver Rag and Hahnemuhle Photo Rag Pearl quite soon, to get an idea of how I like printing on two definitely-OBA-free papers.  In the meantime, feel free to keep the discussion going if you wish; it's quite fascinating.  I might not comment too much, since I'm a novice in regard to many of the issues being raised, but I'll definitely be reading along.

Kind Regards,

Mike

[mike_botelho]

Oh, I'll be giving the Ilford GFS a try as well.   Plus, I see that Harman Gloss FB AI Warmtone will not have OBAs also, but I understand that it's warmer than the GFS for example, and that's not necessarily what I'm looking for.

Just out of curiosity, for those that have tried two or three of them, which is whiter, Crane Silver Rag, Hahnemuhle Photo Rag Pearl, or the Ilford GFS?

Kind Regards,

Mike

[TylerB]

Interestingly it took a lot of user reporting before the big H addressed the issue of the coatings hungrily drawing in yellowing chemicals outgassing from adhesives. Even their own packing tape was causing problems. The yellowing could be accelerated with moisture, so often the top sheet from a box, that most able to draw the yellowing gasses through the paper wrapping, would have a lovely bright yellow stain, exactly the shape of the tape on the outside, appear AFTER printing, since the water based ink had helped accelerate the process.
It's good to see they are now supplying this information, and also back then changed packaging tape. Still though, framers, packagers, artists, are not well educated with regard to this, and find themselves with yellow art.

Interestingly Mark, the whitest of those three papers may be entirely subjective. Most might consider the bluer papers actually whiter, while in fact the closest to LAB neutral may seem warmer and therefore not as white.
Ilford and the PhotoRag Pearl measured very near neutral as I recall, my memory of Silver Rag is that it's a bit warmer.
If you search the forum, you will find some comparative LAB numbers for the various paper bases.
Best to get some sample packs and see what you like.
Tyler

[MHMG]

Interestingly Mark, the whitest of those three papers may be entirely subjective. Most might consider the bluer papers actually whiter, while in fact the closest to LAB neutral may seem warmer and therefore not as white.
Ilford and the PhotoRag Pearl measured very near neutral as I recall, my memory of Silver Rag is that it's a bit warmer.
If you search the forum, you will find some comparative LAB numbers for the various paper bases.
Best to get some sample packs and see what you like.
Tyler
[{POST_SNAPBACK}][/a]

I routinely measure paper white lab values (both UV included and UV excluded) as well as maximum printed black to include in my light fade test reports. Paying close attention particularly to the b* (-b values for cool white papers, + b values for warm white)  and delta b* values (i.e., the b* difference between UV included and UV excluded) tells a lot about the role of OBA in paper white properties.  Papers with OBA in the ink receptor coating typically show delta b values greater than 4.0.  Papers containing no OBAs have delta b values no greater than 0.3 and often get a perfect 0.0 measurement. The paper white L* values will give you a good sense of how intrinsically light (bright) the papers are, some papers reaching 98L.  

There are publicly accessible test reports for Silver Rag, HN Fineart Pearl, and Harmon AI Gloss, and a few others that may be of interest to you.

[a href=\"http://www.aardenburg-imaging.com/acceleratedagingtests.html]http://www.aardenburg-imaging.com/acceleratedagingtests.html[/url]

[POAH]

go for one of the warm tone papers which don'thave an OBA's in them

[johncustodio]

Mark-

How do you know whether the OBAs are in the ink receptor coating or in the paper base?

-John