May 31, 2011

iodized kitchen salt can replace bromide

Hi folks,

good news. Thanks to Rob (Robbek) for his inspiration. I used iodized kitchen salt as a restrainer substituting potassium bromde. About 6 g/l may be a good starting point for medium speed films, and 10 - 12 g/l for high speed films. No need to adjust anything else, the pH remains the same. Also much cheaper than peanuts. Bingo.

The blackpoint was misadjusted during scanning by intension to show the perfect even development and not only black borders.

I guess that's a real breakthough for people having problems getting bromide. And the FP4+ and RPX 100 had a very clear base, almost as clear as a transparency film. Semi stand developed like here would have been desatrous if the iodate wouldn't have done the job so excellent.

Since I use about 0.5 g/l pot. bomide compared to 6 g/l iodized salt for medium fast films, and 1 - 1.3 g/l pot. bromide compared to 10 - 12 g/l iodzed salt, the conclusion is to recommend about the tenfold amount of iodized salt compared to pot. bromide as a good starting point. Adjust for your personal needs, more iodate will cause speed loss. So far I have great results with PanF, FP4+, HP5+, Rollei RPX 100, and RPX 400 (see image below) even at 24 °C full stand development. These are all classic emulsions, maybe flat crystal emulsions like Tmax or Delta need an adjustment, maybe less salt? And if you use another salt with another iodate concentration you of course have to recalulate the amounts to.

The salt I used was a very cheap one from the supermarket, 500 g for 29 Eurocent. it contains 0,0025 % potassium iodate. The very small amount in the salt is sufficiant. For the experts: the iodate is probaly reduced by the developer to iodide that's known as a strong restrainer in literature since decades.

There's also a salt with iodates and fluorides. I didn't use that, but only iodized salt. Fluorides might cause some trouble, maybe more trouble than benefits, but I don't really know.

Cheers - Reinhold

May 2, 2011

some pictures - Caffenol-C-H

Kodak Tmax100 @  EI 400 (image above) and Rollei RPX 100 @ EI 400 ( image below), developed in Caffenol-C-H with 0.5 g/l potassium bromide. 12 minutes @ 23 °C regular agitation, equaling about 15 minures @ 20 °C. EI 200 would have been better for both films.The Tmax additonally was quite underdeveloped. Bought short before the expiring date he was stored in a small shop at probably unsuitable conditions some years without any cooling. During summer that could have been easily much more than 30 °C, the shop has no air condition. Seems he didn't like that too much. Anyway, I like the pic.

Cheers - Reinhold