Good news: Itís been three weeks, and there is still no evidence of crystallization in the Dimezone-version of Trial-130119. In the past, Iíve always seen crystallization start within a week or two, so itís probably stable.

Crystallization seems to be a function of the alkalinity of the concentrate, and thatís controlled by the ratio of sodium metaborate (SM) to ascorbic acid (AA). D316ís SM/AA-ratio is 2.2/4.5 = 0.489. Trial-130119ís ratio is 1.5/3.5 = 0.429. Iíve noticed a white smudge on the bottom of the beaker when mixing D316 at temperatures over 80C. Thatís the beginning of crystallization, so D316 is on the border. I believe Trial-130119 backs off some from that border, which is enough to allow the use of Dimezone S.

I think Iíll abandon Phenidone and use Dimezone S instead. Hereís why:

1. Dimezone S is obtainable everywhere for a reasonable price. now ships it world-wide. So does Fototechnik Suvatlar, and thanks to Rudeofus for pointing that out.
2. Dimezone S gives a sharper toe with some films. Delta 400 in particular has a significantly softer toe with Phenidone, unless the AA is reduced so the AA/Phenidone ratio is about 70. Dimezone S maintains the sharper toe in the presence of more AA.
3. Dimezone S gives normal fog when used in glycol-based concentrates. For Delta 400, Phenidone raises fog as much as 0.10. For most films, Phenidoneís glycol-induced fog-rise is around .07-.08, but itís as low as .02 for a few films such as Tri-X and Tmax-400.
4. Dimezone S stores better.
5. Dimezone Sís image-quality is at least as good as Phenidone.
6. It looks like the crystallization problem with Dimezone S has been solved.

I can see no reason to use Phenidone. Do you?

Mark Overton