[alt-photo] Re: Coating Silver Chloride Paper - Similar to AZO?

[etienne garbaux]

Francesco wrote:

>Just did a Google search for sources for baryta paper. Could something like
>the widely available Hahnemuhle baryta papers be used? Would coating be
>approached differently with baryta?

I'm unfamiliar with Hahnemuhle baryta paper.  What I mean by "baryta 
paper" is well-calendered, hot-pressed paper coated with a fairly 
thick layer of gelatin heavily loaded with Barium Oxide (turns to 
Barium Hydroxide when you mix it with water) and then rolled under 
heavy pressure.  It is, literally, S-G photo paper before the 
sensitive emulsion (and any topcoats) are applied.  My original 
source many decades ago was a Kodak emulsion engineer who would give 
me butts off their paper line.  My current stash was made by Bergger 
in the '90s -- they sold it commercially for a while, but it hasn't 
been around for ages.  It was reportred to be COT-320 with no 
emulsion, but it always looked just a bit cooler (very neutral white) 
to me.  (Or perhaps the COT-320 emulsion gelatin was slightly 
off-clear in the warm direction?)

If I am not mistaken, the Hahnemuhle baryta papers are designed for 
inkjet printers.  The baryta inkjet papers I have (no Hahnemuhle, 
though) seem to have some sort of subbing over the baryta.  I have no 
idea if that would be detrimental or beneficial to coating a S-G 
emulsion.  Based on the somewhat slimy feel of wet inkjet paper, I'm 
guessing detrimental.  It is possible that the subbing could be 
washed off without damaging the baryta layer, but remember that 
inkjet paper is not designed (and, therefore, may not be suitable) 
for full immersion processing in developer and fixer.

Given proper baryta paper, it is easy to coat with emulsion.  Because 
the baryta layer is gelatin filled with pigment, the emulsion bonds 
fine.  I generally wet, then squeegee the baryta paper before 
coating, although I have also coated dry with no problems (if you 
squeegee the wet paper to glass, it is very flat for coating).

Best regards,

etienne