Digital BW, The Print

Myron wrote, in part:

> ...
> While acid in paper is unquestionably detrimental 
> ... I am not sure it is the only concern.

Definitely true.  The burning out of the optical brighteners will cause the
tone of a paper to shift yellow, and most papers have these.  The OBAs are
dyes that absorbs UV and re-emit as bluish light.  To avoid this shift is
tone, I try to use papers with no OBAs in them.  This yellowing may not be
an "archival" issue, but the shift will probably cause buyers to thing they
were sold cheap paper if they see it.  The non-brightened paper also matches
the mat board better.

Lignin is not only the acid "reserve" in poorly-processed, wood-based paper,
but it is also photo sensitive.  It yellows with light exposure even if the
cheap paper is buffered.  So, while wood-based paper may be considered
"archival" if the paper contains 2% buffering and less than 1% lignin, that
lignin will still yellow.  If there is more than 1% lignin, not only will it
yellow, but the acids it produces will eventually overcome the buffering.

The cotton papers that are buffered actually bleach slightly in my fade
tests.  They do not yellow or turn darker.

>I have noticed fairly obvious yellowing --- or at least darkening --- 
>of supposedly acid free and buffered "conservation board" from 
>Light Impressions. It started out as a "natural" white,
>and became noticeably more ivory in colour. This occurred not only 
>where light hit it, but also where the board was open to the air 
>but not exposed to light in my home (ie, the open 
>back of the backing board for a framed photograph hanging on the wall).
> A few pieces of similar board from the same era that were kept in 
>a drawer do not show similar changes. I do 
>not live in a high-pollution area, although oil heat probably 
>sneaks a fair bit of something or other into my home environment. 

Hmm, that's disturbing.  I use Light Impressions board and have noticed
different batches have slightly different hues, but I've never noticed what
I'd consider yellowing.

I wonder if the wall covering was out-gassing.  Indoor air pollution might
be causing the problem.  When I went through my last home building exercise
I was amazed at how difficult it is to eliminate the building materials that
will outgas substances that are probably not healthy for us or our prints.

Paul
www.PaulRoark.com