Multi-roll small tank consistency problem

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I use a Paterson two-roll tank to develop my B&W film in TMAX and HC-110 Dil B developers. Using both developers I am experiencing a difference in negative density between the top and bottom rolls in the tank. When I develop two rolls in the tank, the top roll results in significantly more dense negatives than the bottom roll, which looks quite right. I use 600ml of developer and am quite certain the solution completely covers both rolls. Any suggestions as to why this happens or what I can do to correct it?

Thanks, Robert

-- Robert Vinyard (rvinyard@worldnet.att.net), April 01, 1999

Answers

How do you agitate? Iuse the much maligned reel twirler. Four gentle back and fourth 1/2 turn motions that take five seconds every 30 seconds. I like it because I don't have to take the tank out of the tempered bath each time I agitate.

-- Tim Brown (brownt@ase.com), April 01, 1999.

I use to use a plastic twirl tank and got inconsistent results. Tossed it 30 years ago and got SS tanks and reels. Easier to load and last forever. I bought all new tops($2.50 each) last year for all three tanks and I'll just keep going for another 3O years!

-- Gene (nikonguy@emji.net), April 02, 1999.

I have been using a Paterson 'System 4' 2 roll tank for years and don't believe I've experienced this. I don't process 2 rolls very often so have never really considered this. To make a proper comparision though, you would need to do a test with 2 rolls taken in the same conditions (with the same camera, lense & exposure) to compare the results. I use less than 600ml (about 580 I think) so you've got the film covered. I agitate by giving the whole tank (lid off) a vigorous shake back and forth, a couple of taps on the bench and a gentle twirl with the twirley thingy (about 5-6sec in total) Hey, it works for me :)

-- Nige (nlandgl@eisa.net.au), April 05, 1999.

I've also used the Paterson 2- and 3-roll tanks, for about 25 years, usually with 2 or 3 rolls. There has never been any apparent difference in negative density.

I agitate by inverting the tank, about 1 inversion per second. Continuous for the first 30 seconds, then 5s per 30s.

In theory, 2 rolls in a 2-roll tank will get different agitation, because there is a small air gap at the top of the tank. Inverting the tank will partially uncover the bottom film, but the top one will be permanently immersed. I don't know which film would then get the most agitation, and as I say, I can't see any difference.

Robert: has this only happened once, or is it consistent?

-- Alan Gibson (Alan.Gibson@technologist.com), April 06, 1999.


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