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Tuesday, June 06, 2006

OBAs (Optical Brightening Agents) 101

Uwe Steinmueller has posted an interesting note about optical brighteners over on Outback Photo, for those of you who profile'n'print.

I don't know if it holds true for digital printing papers, but with the old Baryta silver papers you could see the OBAs under black light. And with some papers (I am here to witness), you could see them streak and eventually wash out of the papers with extended wet times! Yowzuh. When printing on the original Ilford Galerie, I used to strictly limit wet time for that reason. It was one of the reasons why certain anal-retentive Zonies slandered that fine paper, because they would wash it for eight hours as a matter of course and wash out all the OBAs.



Anonymous Mike Sisk said...

I don't know about printing papers, but back when I worked as an environmental geologist a black light was a good tool to have.

These OBAs are fluorescent white dyes and are present in nearly all laundry soaps and detergents to get those "brighter colors and whiter whites". If we suspected a body of water might be contaminated with sewage a quick test was to submerge a piece of surgical cotton for awhile then pull it up and check it with the black light (with a control sample to ensure the cotton didn't contain OBAs to start with). If the cotton now had an obvious "glow" we would collect samples for in-depth chemical analysis.

3:16 PM  
Anonymous Anonymous said...

A couple of points aside from the eventual fading of the OBA's.

1. Some manufacturers (apparently through the quality of their processes and materials) are able to get a much "whiter" non-OBA paper base than others, e.g. Crane and Arches among others. While these may still be slightly on the warm side I tend to think of them as neutral rather than warm. (many other non-OBA papers a really quite warm by contrast).

2. Without any real scientific basis, but based on years of inkjet printing and profiling, I am of the opinion that the UV nature of the OBA's often combines with certain inks to make metamerism, and especially what I call "magentaism" much worse. As a general rule, I have found non-OBA papers exhibit far smaller (and less objectionable) changes in hue going from one light condition to another. e.g. from daylight to tungsten or to fluorescent

tim a

4:30 PM  
Anonymous Anonymous said...

Must be the current hot topic. Received this eMail last night, out of the blue - same as anyone else who signed up for their newsletter.

"The Truth About Optical Brighteners in Hahnemuhle Paper
June 4, 2006

There has been growing concern recently about the use of Optical Brightening Agents, or OBAs, in digital fine art paper. More and more often we hear the question, “Are your papers OBA free?” The answer is, “We offer options both with and without OBAs.” Because of a misunderstanding of OBAs, many people are surprised to hear this response. Please let us explain...
OBAs are white or colorless compounds that work by converting ultraviolet light into visible light, thereby making the paper appear brighter or whiter. They do not change the color of the paper; they only fool the eye into seeing a whiter color. After being exposed to UV rays for a long period of time, OBAs will begin to lose their fluorescent quality, leaving only the natural base color.

There are several methods for adding brighteners to digital media. Some companies use the less expensive method of putting OBAs into the receptive coating. Because it is not know what effect, if any, spent OBAs will have on inks, we add them directly to the paper, ensuring that they never come in direct contact with the inks.

Some of our competitors claim that only OBA-free papers meet the Library of Congress Standard for Archivability. However, this standard refers only to boxes and paper used for storage. A better standard by which to measure photographic paper is the Library of Congress Standard for Paper Permanence, which does allow the inclusion of brighteners. All Hahnemuhle papers meet this standard.

So the claim that OBAs cause paper to yellow or reduce its permanence is simply wrong. Eventually, the perceived color of the paper will revert to the same base color as papers without; but initially, OBAs allow a much brighter base. It is not yet known how long the reversion to natural might take. We do know that it is not an immediate thing; it could take as many as 50 years (even longer if the artist takes measures to protect the image from the effects of UV rays.) But the point to remember is that the paper will end up the same color as it would have if OBAs were not used.

Consider that virtually all silver halide papers used in darkroom photography contained OBAs. Artists who wanted a bright white base simply accepted the fact that there would be a slight change over a long period of time. In fact, many photographers and collectors find this “mature” look desirable. At Hahnemühle, we strongly feel that to provide the paper base color and print color where the artist wants it for their lifetime is better than having it wrong from the beginning.

Another important benefit of adding OBAs to digital papers is batch consistency. By adding OBAs, we can assure that your image remains true without having to reprofile every time you purchase paper from a different batch.

For more than 400 years the Hahnemühle mill has dedicated itself to providing the highest quality paper products. We take great pride in the product that we provide—our reputation depends on it. While we could certainly jump on the anti-OBA bandwagon, we remain steadfast in our commitment to the artist’s choice. Ultimately, we do not cater to hype; we cater solely to creativity and quality. We will therefore, continue to provide superior media with and without OBAs."

6:59 PM  
Blogger Uwe Steinmueller said...

>As a general rule, I have found non-OBA papers exhibit far smaller (and less objectionable) changes in hue going from one light condition to another. e.g. from daylight to tungsten or to fluorescent

Interesting observations, these light source have a different intensity of UV for sure.


11:33 PM  
Blogger Dirk said...

An easy way to see what a paper that contains OBAs would look like without the presence of the OBAs is to put the paper under a sheet of Acrylite OP3 plexiglass. This plexiglass is often used in museum framing applications due to its UV light blocking nature. By blocking UV light it essentially negates the effect of OBAs.

10:43 AM  

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