April 2006 - Alt-photo-process-L: Re: Ammonium vs potassium dich

From: martinm ^lt;martinm@gawab.com>
Date: 04/03/06-04:07:37 AM Z
Message-id: <000201c65707$10af7680$959a4854@MUMBOSATO>

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, April 02, 2006 4:23 PM
Subject: Re: Ammonium vs potassium dichromate -- Bolte

> Thanks, that's helpful. Do you also question their finding that
> ammonium dichromate produces more insoluble PVA and that the reason
> for this is that the ammonium cation is involved in crosslinking?

I always assumed ammonium dichromate was more "reactive". That's why I would
expect ammonium dichromate to produce more insoluble PVA. Derived from
silver halide emulsion making, I guess the ammonium cation may affect
diffusion speed. That would suggest the ammonium dichromate is penetrating
the colloid at a faster rate than potassium dichromate.

Martin
Received on Mon Apr 3 04:17:33 2006