Digital BW, The Print

On Sun, 31 Aug 2003, Paul Roark wrote:

> 
> Note that Wilhelm appears to have changed his prediction for EEM.  He now
> gives the paper a 110 year dark storage estimated life.  See:
> 
> http://www.wilhelm-research.com/ep9600%20print%20permanence.html
> 

I noticed that too and was very surprised.  

His notes indicate that he runs his dark storage test at a constant relative humidity of 50% and that higher temperatures and higher RH could cause accelerated yellowing.  The big unknown here is how much does yellowing accelerate with higher RH.

Also, his dark storage test applies to prints that are framed, boxed, or sleeved to protect them from the open atmosphere.  He does mention that low-level air pollutants may cause, "significant yellowing within a relatively short period of time."  Again, we don't know what level of pollutants or how much it accelerates yellowing.

The only test where he uses unframed prints is his "bare-bulb" test; EEM B&W prints still did rather well in it, but again that uses a constant RH this time at 60%.  Also, I would bet that the air in his test lab is of fairly high quality.

I think the air quality issue could explain why people see results that often appear contradictory to Wilhelm's published data.

--Tom