Surge Marks w/ Jobo and Unicolor Base

[mprice]

So, as the title says, I've recently started having some troubles with my negatives and thought someone here might have the solution. Some quick background info:

I've been developing my own negatives (B&W - 35mm, 120) on and off for about the last 15 years, always with steel tanks and reels - never had anything but great negatives. About 6 months ago I got decided that I had had enough of the hand agitation and that it would be great to be able to use my Unicolor base to do more rolls at a time.

I started with a Unicolor film drum and reels which worked out alright for 35mm but left streaks along the edges of 120, something to do with the reels apparently. I switched to Jobo and am using the 2500 series tank that holds 5 35mm rolls. Overall the negatives are coming out alright but I'm noticing that there are portions of uneven sky in my 120 and last night found surge marks from the sprockets on my 35mm. I initially thought it must be from over agitation as the base is always spinning but after some hunting around it appears that these marks really come from not enough agitation. The strange thing is that there doesn't seem to be any pattern to the portions of the roll that have the problems. The base reverses and the one thing I can come up with is that maybe because of the amount of rotation between reversing (due to the size of the drum, maybe 1-1/8 rotations) a portion of the roll is getting too much or too little of something. If this is the case, anybody know if modifying the base to not reverse will help (do Jobo systems reverse?)? One other idea would be to modify the base so it spins further, no idea how or if that's possible.

More info:

Tri-X 400 - 35mm and 120
D76 1:1 (freshly mixed last week, stored airtight, etc) - 10 minutes
Stop - 45s
Fix 1:4 (fresh as well) - 7 minutes

Any ideas or help would be greatly appreciated....thanks.

 

[Bob Carnie]

We solved all mottling, uneven dev problems on our Jobo's by manually agitating the first 15-30 seconds as if you had stainless steel tanks with inversion and twist and a sharp tap after each cycle.
Kind of fly's in the face of having a rotary system but after thousands of runs it works.

 

[mprice]

Thanks Bob, were you using the larger Jobo tanks that are made specifically for rotary processing (2500 series)? If so, did you have any trouble with the amount of chemistry in the tank not being enough, I'm read that you shouldn't use the larger tanks for hand processing but am guessing this is because the lesser amount of chemistry won't work while the tank sits still, and would be fine while it's being agitated - I'm using 800ml for a full tank where 640ml is recommended.

 

[Bob Carnie]

Yes I am, I always use 1000ml per chem so there is no issue of not enought chems.

Thanks Bob, were you using the larger Jobo tanks that are made specifically for rotary processing (2500 series)? If so, did you have any trouble with the amount of chemistry in the tank not being enough, I'm read that you shouldn't use the larger tanks for hand processing but am guessing this is because the lesser amount of chemistry won't work while the tank sits still, and would be fine while it's being agitated - I'm using 800ml for a full tank where 640ml is recommended.

 

[mprice]

Thanks for the advice, I'll give that a try and see if it works, otherwise I might have to go back to hand processing....we'll see.