Re: Dry Plate Speed & Shelflife

From: MARTINM <martinm@SoftHome.net>
Subject: Re: Dry Plate Speed & Shelflife
Date: Fri, 04 Mar 2005 09:18:41 +0100

> I don't see any particular difficulties with that.

In conventional emulsion, large grains refer to 1 micron or larger in
diameter. Can you make grains that big by bathing method? Did you try
it?

> For the making of ultra-fine SH emulsions the challenge consists in
> forming very small grains and keeping them small.

What's your definition of ultrafine?

I described a couple of ways you can do this with various grain growth
inhibitors in my previous email. Modern emulsion chemists have a list
of chemicals that can be used to inhibit growth of grains. They also
have a much better understanding of how to control growth, because a
lot on this had been studied after Berry's model.

> I have at least one paper that indicates a connection between HIRF and
> reduction sensitization...

HIRF is commonly dealt with electron trap (like iridium) doping and
gold sensitization. Gold alone is pretty effective. Reduction may
increase or decrease HIRF, depending on some factors not yet well
understood.

> Probably not. It has been a couple of years since the last time I
> used an enlarger, but I believe to have had access to a 150 W (= 150
> 000 mW) light bulb then. Optical losses run high in both cases. Even
> considering the large bandwidth (and the large part wasted in form
> of heat) of an enlarger's light source, I still have to get along
> with my few milliwatts (per cm/2) only...

Can you speak in terms of lux seconds of exposure? My enlarger has
150W bulb but with a negative in place, I only get a fraction of a lux
at midtone of the image when projecting an 8x10 area.

> Speaking of SH emulsion making, I just wanted to point to the
> possibility of reaching the same goal by different means.

If you are saying you can make very usable plates of ASA speed 10-50
by bathing method, I would like to see how.

--
Ryuji Suzuki
"Well, believing is all right, just don't let the wrong people know
what it's all about." (Bob Dylan, Need a Woman, 1982)