RE: Dry Plate Speed & Shelflife

Robert,

There are a lot of discussion elements in your summary below. Let me try to
address them topically:

Historical dry-plate speed vs. wet plate
As a wet plate photographer shooting historical emulsion recipes I can tell
you that the 7 stop difference is probably not correct. Most descriptions of
wet plate emulsion speed lists it as somewhere between 1 and 3--very slow.
Any wet plate artist will tell you that in reality it is much slower--most,
like myself, gave up trying to measure it--it's damn slow! The vintage dry
plates I see on eBay I believe have an ISO of 25-50. One of the challenges
of the historic emulsions is they are mostly responsive to light in the blue
and ultraviolet spectrum which adds an additional element to consider when
using them.

Bottled Silver Emulsions:
Before learning the wet plate process I toyed with liquid emulsions on
glass. I recall the ISO being somewhere north of 500--much faster than
traditional wet or dry plate. If you are interested in this technique I
would direct you to the following url and book:
http://www.alternativephotography.com/process_dryplate.html
Reed, Martin; Jones, Sarah
Silver Gelatin: A User's Guide to Liquid Photographic Emulsions

Contemporary Dry Plates (not bottled emulsion on glass)
There are folks making contemporary dry plates using historic emulsions.
Most are frustrated wet plate photographers who live in climates where it is
very cold a good part of the year and shoot outdoors, thus they are unable
to shoot for months at a time. You can find several discussions on this
topic, and specifically the shelf life of their poured plates, by searching
the forum using this url:
http://www.cwreenactors.com/cgi-bin/collodion2000/dcboard.cgi

Mark

-----Original Message-----
From: Robert Newcomb [mailto:newcombr@uga.edu]
Sent: Tuesday, March 01, 2005 8:53 AM
To: alt-photo-process-l@sask.usask.ca
Subject: Dry Plate Speed & Shelflife

I've been interested in making my own glass dry-plates to shoot in
camera - I like some of the "errors" introduced from hand poured
emulsions.
A couple of questions for all you knowledgeable people out there.
1) I have read that the speed of early dry-plates was about 7 stops
slower then the wet -plate process in use at the time. While I'm
certainly not trying to shoot action sports shots, we're talking Very
slow here. I have heard that the bottled silver emulsions have an in
camera speed of about ISO 1/2- maybe 1.
  Is their a component (bromide?) or procedure that will make a hand
poured dry plate at least as fast as wet plates?
2) I have also understood that early dry plates (hand poured) had a
useful shelf-life of only a few days or a week after being made in
which one must expose them. Is their a means of extending this
shelf-life to a couple of weeks or at least something more the a few
days? I'd hate to make them and then not be able to go out shooting
the next day so the plate spoil.
I understand that commercially prepared plates later overcame these
factors but what is possible of the home brewer?

Thank you,
Robert Newcomb
Received on Tue Mar 1 14:41:37 2005