more Hahnemuhle Photo Rag yellowing info

The following are excerpts from the latest CoOl conservation website discussion

of yellowing:

Through research I have obtained the following information:

 

* The OBA's are causing this effect

 

* The OBA's alter the reflection of ultraviolet light in such

a way as to make the paper appear cooler white

 

* The yellowing occurs in paper which is stacked or contained

(apparently it has to do with out-gassing)

 

* exposure to light and air will get rid of the yellowing

>

> What I am looking for is a better understanding of the cause and

> possible treatment. There is a lot of money tied up in the project

so reprinting is the least attractive option. We would like to

> light bleach the pages and then proceed with the binding. I have

> experimented with a UV light (I don't know if it is UVA or UVB) and

> it has gotten rid of some of the yellowing. It is very slow and

> possibly I don't have the right UV bulb. After exposing some of the

> pages to natural light the yellow has dimensioned more evenly and

> perhaps a bit better than with the UV bulb, but the edition is large

> and natural light would be difficult. I have thought of grow

> lights for plants and sun-tanning lights as possibilities. We can

> rig up florescent lights and put the right kind of bulb in, if we

> know which one to use.

 

This is indeed a very curious phenomenon that I have heard about

from a number of printers who print for artists on a large scale.

Every now and then a print or a batch of prints will yellow when

kept in drawers or in folders, in any case when *not* exposed to a

source of light. By simply leaving the prints out on a table top for

a few days the yellowing disappears.

 

This being said, I am not sure which mechanisms are at work here and

if the yellowing will reappear later. There is a publication of a

German study that has shown that as the OBAs in inkjet papers are

used up during exposure to light, the papers appear yellower, which

seems to make sense. However, it is stressed that measuring this

loss of blue (it's not really yellowing when you think about it) can

be quite difficult since the OBAs react differently to different

types of light, depending on UV content.

 

I realize this doesn't really help you with your problem. I would

recommend that you speak to a number of digital printmakers and ask

them if they have had this problem and what they have done to remedy

it. It would be good to get to the bottom of this problem that seems

to be quite common, especially in regards to the Hahnemuhle Photo

Rag paper, since so many artists and photographers are using this

paper. It is interesting to hear that the yellowing is apparently

not a function of the inkjet coating, since you mentioned that you

had used the paper base only.

 

XXXXXXXXXXXXXXX

Photograph Conservator

XXXXXXXXXXXXXXX

20357 Hamburg, Germany

Bruce: Are you actually experiencing this with HPR? I've never seen it after using it for about five years. I know several fine art printers who use HPR and consider it quite archival. HPR does have a minimal amount of OBA's.

 

I get very curious when I see phrases like "get to the bottom of this problem that seems to be quite common".

Bruce: What I understand is that the optical brighteners bleach and become less fluorescent

over time. Paper that had a lot of blue cast from the OBA fluorescence will now appear more

yellow (actually it is less blue) and there probably isn't much you can do about it. As for

putting it in UV lght an having the effect disappear that mechanism makes no sense, I would

think that a bright UV light would after a while make it worse. The thing that I think most

older printers recognize is that most of the basee paper used in traditional silver gelatin

printing had loads of OBA as well and they all yellowed just a bit.

Bill

Bill, I agree with you. Bob, I don't use the paper. None of the above represents anything I've said or personally experienced about the paper. This is a conversation by several other conservators on a listserve I subscribe to. I put the information out there for people to do with as they wish. I can't see not posting this simply because I haven't personally experienced it. I think that's irrelevant. These are conservators and conservation scientists. They don't necessarily see things through the same lens as photographers or artists, but on their side of the equation they pretty much know what the hell they're talking about. I think in a case like this one can't suffer from TOO MUCH information.

Also, light bleaching with UV is pretty common with paper conservators. We also sometimes use "sun" bleaching in an alkaline environment which, remarkably enough, can be fairly closely controlled. If the paper is lignin-free light bleaching has minimal reversion. It is true, however, that light bleaching paper that has lignin will only lighten in the short term, and will most likely lead again to darkening over time, sometimes worse than the original discoloration.

Just doesn't happen with my silver coated fibre based papers. They don't have the fading problems I have seen with so many digital prints either.

Dakotah:

There is fading which is well known and well documented, but almost every guy that I have

talked to with black and white silver paper experience has said that there is a bit of yellowing

with these papers too.

BVA