Digital BW, The Print

Paul Roark wrote:

>
> The sepia tone I ended up with was set after studying my own samples 
> of old
> photos and a number of books.  I thought the most authoritative was a 
> French
> government sponsored History of Photography.  I figured they had the  
> money
> to make the best reproductions.  One thing I think I saw was that the very
> common albumen prints seem to become more yellow with age or light.
>

This may be very basic stuff for many here, but with the size of the 
group, I thought it might be good to take a moment and cover this ground..

"Sepia:"

What is it really?

To my knowledge there are four different, but. at times. quite visually 
similar, processes that result in "sepia" images.

1)    Fading and sulfidization of silver gelatine prints - in this 
process exhibited by many older prints, both airborne sulfur ions and 
sulfides left in the print by improper fixing, clearing, and washing 
will combine with the image silver  - in such a case, the sulfide ion 
joins the silver molecule and a more stable silver sulfide compound is 
produced

2)    Fading and yellowing of albumen prints -  residual sulfates and 
thiosulfhates from developing that remain in the paper cause yellowing 
of the paper itself and as in #1 join with image silver to form silver 
sulfides

3)    Van Dyke Brown/BrownPrint  -   A process in which an image is 
initially exposed onto silver salt sensitized paper and then developed 
in a thiosulfate solution -- the sulfur joins with silver of exposed 
silver salts in the actual developing of the print - this forms a 
brownish image of Silver Sulfides

4)    Sepia Toning - After exposure, developing, and fixing of a 
gelatine silver print, a sulfide or polysulfide solution is used to join 
sulfur to free silver molecules in the image - the longer the toning, 
the more sulfide molecules created in the print, and the more brown the 
final image

The variety of  tonalities of "sepia" prints may, in part, be traced to 
the fact that "sepia" is really an inexact term describing the end 
result of these different processes..

 In fact, the tonalities are even wider than it seems.. As in #4 above, 
the final results in hue (more or less reddish or olive-like) depend 
upon not just the actual toning, but, will appear differently in 
chloride or bromide papers AND depending upon what the actual developer 
was  (warm-tone or cold-tone developers  mated with sepia and differing 
paper types will give differing hues)

We also generally tend to think of selenium toned prints as purplish or 
exhibiting "colder" tonalities..  In fact that is only true with Bromide 
papers -- chloride papers when toned with selenium can go to a reddish 
brown and be mistaken for sepia toned images.  Moreover, with some 
chloride papers and a warm-tone developer (PQ or Agfa) followed by 
Selenium toning, I have toned silver gelatine prints to a near 
orange-red image.

Sepia toning, selenium toning, gold toning, etc., were developed out of 
a need to make silver prints more archival, by preventing image silver 
from oxidizing.

Given the preceding it should be clear why sepia tonalities are really a 
personal taste, like the choice of cold or warm base papers, etc.  The 
causes of traditional  "sepia" images are varied, and concomitantly, so 
are the tonal and hue ranges that would be covered by the rubric of 
"Sepia"..




[Keith]
 
 

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