View Full Version : C 41/810/JOBO tank question

29-May-2011, 18:35
I searched..... :)

I am using a jobo 2830 tank on a unicolor bi directional base. I have done many sheets of 810 in BW with little or no streak issue. Skies seem to look great

I just shot some porta 160NC and got some streaks. The photo below shows the streaks and uneven areas. I used the tetanal kit fresh.

I did presoak by filling the tank with 104' water and let it sit for about 1' 30".

So pre soak or not? I seem to find many different opinions over the years of threads on these subjects.

My thought, for what it is worth, is that the presoak is not the issue. My working solution bottles contain about 520-550ml of solution. I remember when I pored the developer in I overfilled the cup in the JOBO and some of the developer ran into the tank while the remaining 20-30ML were filled into the cup. This would result in maybe 20-30ml of developer hitting the film maybe 10" sooner.

The presoak seems to be the issue I found most in the different threads I found.

I have done this many times with BW 810 with no issue but the C41 810 is new to me.



http://farm3.static.flickr.com/2265/5774139842_87a9619f7b_b.jpg (http://www.flickr.com/photos/53092319@N04/5774139842/)
0511 7 CLR 810.jpg (http://www.flickr.com/photos/53092319@N04/5774139842/) by urbanlandcruiser (http://www.flickr.com/people/53092319@N04/), on Flickr

Daniel Stone
29-May-2011, 20:05
1st off:

the developing time for c-41 is MUCH shorter(3:15 for "normal") than for most B&W film and developer combos. This leads to higher rates of mottling(like in the top right of your posted picture), due to less time in the developer. 10" doesn't sound like much, but out of 3:15", its a pretty large amount of time.

Pre-soak? I've found that I get smoother results(especially with LF, and in particular, with 8x10) WHEN I pre-soak vs not doing it. 104F is a bit too hot, try 101F or 100F. I pre-soak for 1min TOTAL(2-30s baths total time, not counting filling,but draining yes). And keeping the drum HORIZONTAL(I use a 3005 now, but for a while was using a 2551 drum 1 sheet at a time) while filling is imperative. And make haste when filling, but don't spill it. Be precise and fast, but not too fast that you're spilling chems.

I now use a friend's Jobo or send out for my c-41, but could make do with the old methods(not w/o the 3005 though) if need be.

best of luck!