Re: possible answer to archivalness comparison between carbon gum andpt/pd

[etienne garbaux <photographeur@nerdshack.com>]

Sandy wrote:

> I am currently making a very thick carbon tissue (weight height of 
> about 1mm) for negatives with a log density range of about 2.7. With 
> the correct sensitizer
> this tissue is capable of prints with great relief. I push the 
> envelope on this since relief is one of the most distinctive 
> characteristics of a carbon print.
Some of the 19th century examples I have, and others of that era I 
have seen, have deepest shadows around 0.075" (nearly 2 mm) above the 
substrate.  Around 0.035" to 0.050" seems more typical in that era, 
and some are only 0.020" or 0.030".  The alt-carbon prints I've seen 
in the last 15 years or so appear to have less than 0.010" of relief, 
but I haven't been in a position to measure one accurately.  Some 
commercial tissue I was shown recently looked to have less than 
0.020" of gelatin (again, eyeballed, not measured).

I'm ambivalent about the relief -- as I mentioned, I find it 
distracting if the lighting allows for any specular reflections or 
shadows of the relief from low-incidence light.  I have always 
believed that the best tonality is achieved by mapping the scene 
values to the most extended negative values you can obtain, then 
using a low-contrast printing medium to suit the negative.  (I think 
this is true for pretty much any full-tonal-range medium -- certainly 
carbon, Pt, kalli, and cyano in my experience).  So, I favor fairly 
thick tissue, but not because it makes prints with lots of relief.  I 
actually stopped making carbon prints for a time after I started 
making monochrome dye transfer prints, which have a very similar 
tonality but no relief in the finished print.

Best regards,

etienne