Archived posting to the Leica Users Group, 2007/08/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I used to use pyro-acetone a lot. Wall and Jordan (Photographic Facts and Formulas, a classic reference tome) said that it was useful for glass plates (specifically recommended it for lantern slides) but didn't recommend it for "modern" films. The fact that their last edition (not including the later John S. Carroll edition - of which I couldn't figure what had changed from the previous) was published in 1947 might shed some light on what they meant by "modern". I suspect that the acetone had a way of dissolving cellulose nitrate, but leaves current bases unscathed. I have never had a problem with it. Of course, some people might object to losing close to three stops something of a problem. Generally, I don't. You could use Pan F or Tri X. Maybe at the same ISO. I wouldn't use Pan F with it. I don't want to shoot at ISO 5, or even 7. Where did the lost speed go? Simple. It transforms magically into really great shadow detail. When I processed sheet film in PA I either used a tray or processed it in the Merz processor, an internal drum in which the chemicals lay in the bottom as the drum rotated and rocked -sloshing around. In both cases, there was a great deal of surface area per unit volume, meaning lots of aeration. That resulted in a great deal of staining. Processing in a small tank did not produce as much stain. I rather liked it both ways, actually, but there is a difference. PA was incredibly useful and once saved my neck big time on a job, when I forgot that I was shooting Tri X in the M4 when I had my meter set for Kodachrome 64. The result was stunning. NO visible grain and the most gorgeous tones you ever saw. Subject: shovel with foot pressing on it making hole in dirt. It was a how-to sequence for a garden job. ISO 64 was just right for tri-x (non professional; I like the amateur emulsion a lot better anyway. Besides, I could buy it in Friday Harbor WA, where no one had ever heard of Pan F). The point here is that you can have the stain you want. Put a piece of exposed film end into a bit of it in a graduate containing your pyro developer; you can see the oxidation products stream off. It oxidizes like mad, and that seems to make the stain happen. Not enough stain? Rot the developer a bit. Leave it on top of the water heater for 15 minutes exposed to the air. Throw a little acetone in it, that works, too, but it would change your development time. Acetone, as I understand, reacts with the sodium sulphite to produce some sodium hydroxide. If there is a chemist in the group, I wouldn't mind hearing more about it. When you put acetone in it it feels slippery, which indicates a base. I do know that if you put a bit of acetone in dektol, it makes a pretty good sheet film developer at about 1:9 and it feels slippery, just like it would if you mixed NaOH with water. I'm real familiar with this because I also use Windisch pyrocatechin, which uses 10% NaOH as the environmental variable. OK it is toxic. I wear gloves. Just respect the chemicals. Personally, I think that the stain is over-rated somewhat. On the other hand, one colleague for whom I used to process film called me a while back complaining that the negatives he processed himself didn't have that quality that he loved, as mine did. Maybe not. But I like the quality of those pyro negatives even when the stain is minimal. I don't know what it is, exactly, but at best, when enough exposure is given, the shadow detail is incredible, only to be surpassed in the incredible sector by the amazing whites. I found a fluorescent plastic Donald Duck on a beach once. Unbelievable!