Did you really mean to say 1ml of H2O2 per 1ml of sensitizer? A few years
ago, when I was trying to correlate the range of contrast control using
peroxide as compared to chlorate (after reading your View Camera article), I
found maximum effect to occur at about 0.5 ml H2O2 per 1ml Ferric Oxalate.
In actual practice, I rarely find that I need more than a drop or 2 per ml
if the negative range is where it should be. A typical mixture for an 8x10
image would be 1ml ferric oxalate + 1 drop H2O2 + 1ml palladium solution. I
rarely use platinum as I prefer the warmer color of palladium in most cases.
Another observation was that the chlorate method yielded a noticeably warmer
image color than either peroxide or dichromate methods. Subtle but
noticeable nonetheless.
Keith
-----Original Message-----
From: John Rudiak <wizard@laplaza.org>
To: alt-photo-process-l@sask.usask.ca <alt-photo-process-l@sask.usask.ca>
Date: Sunday, May 10, 1998 6:56 PM
Subject: Re: peroxide
>I have had much more success putting the peroxide in the sensitizer. It
>is more consistant and controllable. The peroxide in the developer
>tends to decompose and it is very difficult to put out an edition with
>this method. I use a cold tone developer (140 gm. potassium oxalate,
>20gm. disodium phosphate, 5gm oxalic acid/ 2L distilled water), and a
>Pt/Pd ratio close to yours. When adding to the sensitizer, add the
>peroxide to the ferric oxalate, stir, then add the platinum/palladium
>mixture. This lessens the tendency of the platinum acting as a catalyst
>and decomposing the hydrogen peroxide. 1ml. drugstore peroxide per ml.
>of sensitizer should give a considerable boost in contrast. You can add
>more if you like. The peroxide doesn't cause grain increase like
>chlorate.
>
>Good luck!
>
>John
>
>Which intensifier are you using for your neg?
>--
>Alchemy Printmaking & Photography
>PO Box 633 Ranchos de Taos, NM 87557
>http://www.quetzl.com/Alchemy/html.index