Re: Modifying bleaches

"I thought we were talking about printing paper
emulsions."

I hoped to have pointed out I had little experience with paper emulsions...

"This stabilizer reduces too much speed in bromide emulsions so I don't use
it in them."

I understand some authors - e.g. Glafkidès, Frieser (?) - suggest there are
a
few stabilizers that don't lower speed.
Apropos, why do you have to add a stabilizer? Well, I may not know much
about paper emulsions but speaking about ultra-fine grain emulsions, you
don't necessarily have to incorporate stabilizers to prevent fog.

By the way, like Ray, I also wondered about your method of converting AgCl
into AgBr. For spectral sensitization this might have some interesting side
effects - but for paper emulsions???

"How do you measure the degree of conversion? What kind of time does it
take for the conversion to take place?"

Frankly, I don't know how to measure the degree of conversion.
Maybe by looking into the refractive index of the emulsion?

I assume the conversion process essentially depends on variables like: grain
size,
silver concentration, halide concentration of the bathing solution but also
on diffusion speed, which in turn might be related to the
kind of colloid and the degree of hardening.
For the fine AgBr grains, I am dealing with, it only takes a few minutes
to convert them into AgI (in say a solution of 2g KI/L).

Martin

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, November 30, 2004 6:34 PM
Subject: Re: Modifying bleaches

> From: MARTINM <martinm@SoftHome.net>
> Subject: Re: Modifying bleaches
> Date: Tue, 30 Nov 2004 10:20:37 +0100
>
> > It may depend on the specific stabilizer - since conversion to
> > silver iodide can be carried out routinely on commercial ultra-fine
> > grain (and supposedly stabilized) silver bromide emulsions.
>
> I thought we were talking about printing paper
> emulsions. Chlorobromide emulsions usually use much more powerful
> stabilizer than iodobromide emulsions, especially in neutral to cold
> tone papers. I used 1-phenyl-5-mercaptotetrazole at 0.18 mmol/mole AgX
> in chloride emulsion and this halted ripening. And I can't seem to
> wash this stuff off once it's mixed in (as far as I know, fixing the
> emulsion is about the only practical way to get this stuff off the
> emulsion, but that's not useful anyway). This stabilizer reduces too
> much speed in bromide emulsions so I don't use it in them.
>
> How do you measure the degree of conversion? What kind of time does it
> take for the conversion to take place?
>
> --
> Ryuji Suzuki
> "People seldom do what they believe in. They do what is convenient,
> then repent." (Bob Dylan, Brownsville Girl, 1986)
Received on Wed Dec 1 01:35:37 2004