The Truth About Optical Brightening
Agents (OBA's)
Recently there has been a lot of discussion on websites, Internet forums and chat rooms about the use of
OBA's in inkjet canvas media.
One thing common with all those that claim OBA's will cause your image to
change is they never site proof. That is because there is simply no
evidence OBA's will break-down quickly.
After reading the documents below, we think you'll agree there is no reason
to be alarmed about OBA's in the canvas media. In fact, the presence of OBA's
is a good thing. They add 'pop' to the canvas, brighten the white colors and
make the image look better. Without OBA's, canvas media is warm or pale and
does not show-off your image in the best way.
However, if you still want OBA-free canvas, just indicate that in the special
instructions and we'll print your image on canvas that is claimed to be free
of OBA's.
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Exhibit A:
Below is a White Paper from Dr. Ray A. Work. Dr. Work is a Phd chemist and
is generally credited with inventing ink-jet printing. He holds numerous patents
in printing technologies and is an advisor to many print and canvas media companies.
White Paper March 5, 2009
Title: Organic Optical Brightening Agents (OBAs) in Fine Art Ink Jet Media
Author: Dr. Ray A. Work, III (see www.workassoc.com )
Introduction
Within the fine art reproduction community there has been increasing interest
and discussion concerning the pros and cons of using OBA containing ink jet
media for fine art reproductions and long lasting photo prints. Many statements
have been made which suggest that these additives will cause the prints to
have a very short life before fading or yellowing will occur and that “OBA
free” media are the only media which will be truly archival. This white
paper is intended to shed some light on this subject and to put to rest the
fear that OBAs are evil and must be avoided. This is not just the opinion of
a PhD Chemist who has spent more than 30 years in the ink jet technology field
but is backed up by independent laboratory test results.
What is an OBAs?
Organic Optical Brightening Agents are organic dyes which absorb ultraviolet
light and reemit that light in the blue part of the visible spectrum. The result
is whitening and brightening of the media into which they are incorporated.
To achieve a white media OBAs need to be used since the cotton and/or paper
fibers and the coatings applied to them are inherently yellowish or brownish
due to the reflective nature of these materials. Only with the addition of
OBAs is a bright white media possible.
Upon exposure to light and heat the OBAs can lose, over time, their ability
to fluoresce and add blue light to the reflectance spectrum. The result is
reversion to the original color of the materials which make up the media and
its coatings. It is very unlikely that these OBAs will themselves turn yellow.
Choice of OBA and the amount used along with it’s location in the final
print effect the rate at which this occurs. In our modern ink jet fine art
papers and canvases the OBAs chosen along with high quality paper and canvas
substrates and coating materials generally result in excellent print longevity
with little risk of yellowing due to the OBAs fading over the life of the print.
What products contain OBAs today?
Most fine art papers and canvases contain some OBAs in order to provide a
white and not a cream or yellow substrate. If the whiteness or brightness of
a paper or canvas is greater than 90% there are most likely OBAs present. In
paper OBAs may be in the paper itself or in the coating on the paper or both.
Below are several examples of OBA containing papers and their Wilhelm Imaging
longevity ratings (see www.wilhelm-research.com )
For display under glass using an Epson Stylus Pro 9600 with OEM inks Henry
found that Epson Premium Semimatte Photo Paper will last 67 years, Somerset
Velvet for Epson will last 62 years, Epson Enhanced Matte Paper will last 76
years and Epson Velvet Fine Art Paper will last 61 years. With UV filtration
each of these exceeds 100 years and their dark storage performance is over
200 years. There is no evidence from these data that OBAs will cause these
papers to yellow or the prints to fade in only a few years as some people claim
they will.
In this same study with papers that contain no OBAs similar or slightly better
performance was observed. Epson UltraSmooth Fine Art paper will last 108 years
and Epson Textured Fine Art Paper will last 82 years. With UV filtration each
of these exceeds 150 years and their dark storage performance is over 200 years.
Only canvases without OBAs were tested and they showed similar results to the
OBA containing papers. PremierArt Water Resistant Canvas for Epson will last
75 years and Epson Canvas will last 69 years. With UV filtration each of these
exceeds 100 years and their dark storage performance is over 200 years.
So from this study there are no indications that the OBAs significantly affect
print longevity and certainly do not cause rapid image fade or yellowing in
only a few years.
What about protective coatings?
To increase the longevity of prints whether on canvas or on paper a protective
spray or coating may be applied. If formulated properly with UV absorbers and
compatible polymers and solvents these materials will further increase the
longevity of the print. By absorbing UV light they protect the pigments and
extending the life of the OBAs present. They will also reduce the brightening
effect of the OBAs by reducing the amount of UV light that reaches the media.
If a slight yellowing is observed when the protective coating is applied it
is likely not due to the coating but the reduction in efficiency of the OBA.
As a result the useful life of the print is extended since both the pigments
and OBAs are better shielded from the UV light which will eventually bleach
them.
Examples of the effect are included in Henry’s study. The coating
effect is related to the uncoated print life and the thickness of the coating.
In
these tests at least 20% longer life was forecast with a spray than without
on the same media. When the protective layer was coated on in a thicker coating
the increase in longevity can be over 100%.
So from this study there are benefits in both OBA containing and OBA free
media if a UV absorbing protective coating is applied. One note to keep in
mind. The choice of protective coating material along with ink and paper or
canvas is very important. The protective coating if mismatched to the ink and
media or if it is poorly formulated it may cause splotchy yellowing or cracking
with age. This has been observed in some cases. Confirm with your supplier
the compatibility of these materials. Do not assume that any overcoat will
work well with every ink and media combination.
Truth in advertising!
I have become concerned in reading literature describing novel whitening
technologies that are not OBAs but make products whiter and brighter and
the claims that
they have better longevity and are somehow better than conventional OBA dyes.
I have seen no evidence that such a product exists in ink jet paper or canvas.
If the product absorbs UV light and reemits visible light it is defined as
an OBA! If in a dark room with UV light illumination it glows then it contains
OBAs. The OBA may be in the paper under a coating layer free of OBAs or a canvas
where the gesso layer under the ink jet coating contains the OBAs. In these
cases the claim that the product is “OBA free” is not credible.
Claiming that it is somehow better in longevity has not been supported in independent
lab data to my knowledge. Since the “OBA free” papers and canvases
in the above examples are similar to the OBA containing products tested and
with a protective coating they all provide a very long life without fading
or yellowing the advertising appears to be a marketing ploy to promote one
product over another without any proof of the superior performance.
My advice is to beware of smoke and mirrors and be sure you check out the
claims to be sure they are based in science and not just marketing hype.
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Exhibit B:
Below is a Press Release from Hahnemuhle Mill. Hahnemuhle
has been manufacturing papers for over 425 years. They have been using OBA's
in their papers for many years.
"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."
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Should you have any questions, we urge you to contact us at custserv@pictureitoncanvas.com
