Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "john" <deanwork2003@...> wrote:
>
> 
> I totally keep forgetting to ask two things that I've wondered about for a long time,then I'll let this thread drop and get back to work.

me, too.

> 1. Does anyone have any link to concrete scientific fade tests of well processed and washed gelatin silver fiber print material (BW)? It seems like I remember RIT publishing data on silver prints many years ago. What kind of conservation rating would be applied to gs prints?
> 
I can't pull up a reference at this moment, but Arrhenius testing of thermal aging properties has been done. Also, the effects of residual thiosulfate (fixer) in the paper are an ISO standard, but everyone in the preservation field, myself included, always assumed there were no light fastness issues. Although protected by gelatin which is bound to improve OBA stability, the fact that many modern silver gelatin prints contain OBAs does suggest that we ought not to assume.  We ought to run some light fastness tests. It's actually no my "to do" list.
> 
> 2. What about "dark storage" of type C materials like Fuji Chrystal Archive? I remember Wilhelm writing about how well Cibachrome held up in dark storage (hundreds of years) while C prints did not perform nearly as well. So I'm wondering how I Metric relates to dark storage of C prints in average temp and humidity. 

Arrhenius testing works very well to test residual color coupler staining and thermally induced dye fading in C prints. Yes, these tests are convincing and well behaved scientifically speaking, but again, very liberal thermal fading endpoints (25-35% dye loss) are currently used as endpoints. The I* metric, Conservation display rating, and AaI&A test methodology in general could easily be adapted to run thermal aging tests. I have done many thermal aging studies in my time using the traditional criteria. I'd port it all over to the new AaI&A testing methods in a heartbeat were it not for the capital cost of the test chambers (tens of thousands of dollars needed... that's a lot of subscribers, but it could happen!)
> 
> I know one thing all the Kodak C prints I did 20 years ago are all mostly red now, not showable, and were stored in decent conditions, but certainly not cold, dry storage like a museum vault. Friends and colleagues of mine have all experienced the same degradation. But these were all Kodak C prints. I wonder how much the lack of good thorough washing from  commercial print processors (probably contaminated as hell with bleach fix on the rollers) added to this. 
> 

Yes, cyan in general is the most light fast of the chromogenic color dyes and the least thermally stable. Magenta is generally least light fast, but followed closely by yellow. Hence When you see a red shift its thermal aging and consequent greater fade in the cyan dye, when you see blue-green color casts it's light fading with greater fade in the magenta dye and yellow as well. Note: there were some early 1970s chromogenic RC print systems where yellow had some very poor light-induced humidity and temperature fade problems. The titanium dioxide whitening layer produced free-radicals that wrecked the yellow dye, but this problem got solved for the most part.    When Fuji worked to make Crystal Archive more fade balanced (hue shifting is more objectionable to most consumers than contrast changes), they moved ahead in the print longevity race over Kodak, et al. Fuji deliberately selected a less light stable cyan dye, and then developed a much improved magenta dye and stain resistant color couplers.  This allowed a more balanced fade behavior. When you look at the AaI&A light fade test, you see a move in the Crystal Archive towards more purplish-blue in color, but no where near as other brands. Then factor in thermal fade (which you can only do when assuming some mix of light level plus temperature for "average" keeping conditions) and the fade balancing improves the lifetime ratings even more.   I hope this makes sense.  Well documented in the photo conservation literature.


Now, I second your vote to go get some other work done!

cheers,

Mark
http://www.aardenburg-imaging.com