Jobo Expert Drum and uneven processing.

[tim atherton]

looking for something else I happened to come across the Jobo article on pre-soaking:

"To Soak or Not to Presoak

Recently, on the internet, we have seen questions regarding black and white (BW) rotary processing, particularly in regard to Kodak’s Xtol developer. Participants in the internet newsgroup rec.photo.darkroom are quick to point out that we at JOBO recommend that all conventional BW films should be processed using a 5 minute presoak, except for Xtol, but there seems to be a fair amount of confusion regarding the reasoning behind the presence or absence of a presoak.

The story goes all the way back to the earliest days of JOBO here in the USA, about 16 years ago. At that time we wanted to be able to provide a simple starting point for BW film processing. Yet, we knew that the constant agitation of the JOBO rotary processors was going to increase the contrast on any films processed in them. We began exhaustive testing in search of the elusive magic factor which would allow us to say "To process BW films, simply multiply your developing time by X, and your rotary processing will work perfectly."

When we found a factor on one film that worked well for a single developer, we then tried that film in other developers. We quickly discovered that the factor did not translate to many of the other developers. So we reversed our approach and tried different films in the same developer. Again, we quickly discovered that one factor would not work on many different films in the same developer.

Then after a year or two of frustration, one of the technical staff at JOBO Germany told us to try a five minute presoak in water. So we tested a wide variety of films and developers and the vast majority worked well simply following the normal hand-inversion instructions from the developer manufacturer, and preceding it with this five minute presoak. While some of the combinations of films and developers needed minor adjusting, nearly all the tested materials came within 5% of being right on target for delivering excellent results. We also tested shorter presoak times and found they did not work well at all.

So JOBO USA began recommending five minute presoaks for all BW developer and film combinations. Then about 1988 Kodak came out with T-Max films, and for the first time in our memory, a film manufacturer had included rotary developing instructions. Basically they had followed the same instructions we had discovered, and there was no need for any changes.

Then about three or four years ago, Kodak introduced Xtol developer. This time they not only had rotary processing instructions, they also had a whole instruction sheet dedicated just to rotary processing and for the first time in recent Kodak history, they gave instructions for other brands of film, as well as their own. But most importantly for JOBO, they indicated that all their developing times were for use without presoak. THIS is what caused all the discussion on the internet newsgroups. Why should Kodak advocate no presoak when JOBO advocates a presoak?

Go back to the history of the story, and the answer is clear. JOBO was looking for a SIMPLE way to get customers successful in their processing. The presoak provided that simple "common denominator" that enabled us to tell customers, "Presoak for five minutes then process normally."

What Kodak did was an enormous amount of testing, and published the results. Neither method is right or wrong. They both work well. If you are currently presoaking your film and getting the results you like, then keep on doing it. If you are starting without a presoak and you like the results, then keep on doing it. As I’ve said before, photography is not a pure science- it’s really alchemy. Enjoy it.

Note: JOBO does not ordinarily recommend a presoak for color films since it may cause a slight color shift."

[Ed K.]

Good info Tim. I've tried what I would call "pre-rinse" vs. none. Pre-rinse meaning that I run tempered water for 5 minutes in the drum before starting the development. Both ways produce even development, however the presoak usually goes a long way toward dye removal and elmination of the dreaded "purple negs" syndrome. The developer removes dye, however if there is less of it to deal with, it goes away better by the time the full processing cycle is done. Unless I'm using a very mild developer, I get clear negs with no dye. I found no difference in evenness between pre-soaked Ilford and Efke sheet films whether presoaked or not when using a Jobo with expert drums. Ilford does mention a wetting agent in their recommendation not to presoak, right?

[Jan_6568]

Since I got your advices I developed four times in Jobo drum and all of the films were fine. No uneven processing, no noncleared or non-fixed areas on the negatives. Here is what I changed:
1. I loaded the films very carefully, following the Jobo instructions (as Ed suggested). However, the films certainly moved during the processing.
2. I used more of the chmistry volume. Now I use 500 ml per drum regardless how many negatives I process.
3. I extended presoak time to 5 minutes.
4. I fill the drum using elastic funnel

I am not sure which of the above was crucial but it is all right now - once again - thank you very much.