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  #1  
Old 20th March 2018, 10:54 AM
Car Mad Dave Car Mad Dave is offline
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Default C-41 rotary processing - dumb question

I had a go at C-41 processing, using a Digibase 1 litre kit with separate bleach and fix to develop 16 rolls of 35mm and 120. I must say I was impressed with the kit and got pretty consistent results. However, it was a real pain to "manually" maintain temps at 38C so I'm probably going to go the tempered bath / rotary processor (aka JOBO) route in the future.

So here's the dumb question - if I'm using constant rotation do I still use the standard C-41 time of 3:15? I've read a lot about B&W constant agitation in rotary processors re adjustments needed when moving from intermittent to constant agitation but nothing seen re C-41.

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Old 20th March 2018, 11:16 AM
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GoodOldNorm GoodOldNorm is offline
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3mins 15sec is correct for all 100-400 asa c41 films, I use the no.1 speed. Do give the blix a good shake before pouring it in the tank it works better with more air in it, just like red wine.
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Old 20th March 2018, 05:18 PM
Car Mad Dave Car Mad Dave is offline
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Thanks Norm
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Old 20th March 2018, 05:57 PM
John King John King is offline
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I will concur with Norm on this with the exception that I have never seen any alternative development time for films above 400ISO. The Digibase instructions give times as 3m.15s but makes no mention of HS films being every different.
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Old 20th March 2018, 06:29 PM
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If I use 400ASA film and meter it as 800asa I develop for 3mins 30secs.
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Old 22nd March 2018, 05:30 AM
MikeH MikeH is offline
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I process C-41 using Kodak Flexicolor ra chemistry originally intended for use in Rapid Access minilabs, 7 min total process time. I use as recommended by Kodak 3'15" development in my Jobo. Kodak is quite stern in their instructions not to pre-rinse to warm the tank. It's a hard habit for me to break. Because the Jobo solution volume is so low and aeriates the developer, Kodak recommends 1 shot and toss. Same recommendation goes for bleach and fixer. I replenish the Bleach seems wasteful not to. Fixer I use twice then toss. Because you wash the film after fixing no stabilizer is needed, just a final rinse SM solution, I mix with purified water and use for many rolls. The RA system requires 1 minute bleach and I fix for a couple minutes. I rinse between bleach and fixer just to prevent carry over. Best Regards Mike
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Old 22nd March 2018, 12:31 PM
Mike O'Pray Mike O'Pray is offline
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Quote:
Originally Posted by MikeH View Post
Because you wash the film after fixing no stabilizer is needed, just a final rinse SM solution, I mix with purified water and use for many rolls. Best Regards Mike

Mike, what is SM solution? Is it the equivalent of a stabilizer? As far as I am aware the last stage should be stabilizer to prevent "bugs" attacking the film's dyes later.

Thanks

Mike
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Old 25th March 2018, 10:07 PM
JOReynolds JOReynolds is offline
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Quote:
Originally Posted by MikeH View Post
Kodak is quite stern in their instructions not to pre-rinse to warm the tank. It's a hard habit for me to break. Because the Jobo solution volume is so low and aeriates the developer, Kodak recommends 1 shot and toss.
I designed a rotary C41 processor for Bray Imaging in the 1990s, the intended customer Kodak MEA. It was tested in their Harrow training lab and I proved sensitometrically that a pre-rinse gives stable density with variable film loads and very tight control strips. The dev time was always3m15s, which suggests that the temperature was correct and consistent.
If the bleach is well-aerated the lifespan is good - be generous with the volume and recover for reuse. Ditto fix, although aeration is not relevant. Wash normally in several changes.
Frothing in the drum will cause drying marks. Best to remove the film from the spiral(s) with a weighted bottom clip and see-saw through a bowl of final bath (stabiliser). Hang to dry from a dry clip.
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Old 26th March 2018, 06:30 AM
John King John King is offline
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When using stabiliser I have always filled the tank with 300cc of the liquid and let it stand for 2 mins that way there is no risk if frothing and I have always had clear streak free negatives.

As for not using a stabiliser. As I understand it, stabiliser is composed mainly of a week formaldehyde solution and this will make it less appealing to the invasion of fungus that will destroy the image and also reduce fading over time. I cannot say anything about the former because it has never happened to me, but I have a number of films that have faded after quite a short time which were not treated with stabiliser. I now always use it.
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Old 13th September 2018, 06:44 AM
John King John King is offline
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Default Low volume developing

Quote:
Originally Posted by MikeH View Post
I process C-41 using Kodak Flexicolor ra chemistry originally intended for use in Rapid Access minilabs, 7 min total process time. I use as recommended by Kodak 3'15" development in my Jobo. Kodak is quite stern in their instructions not to pre-rinse to warm the tank. It's a hard habit for me to break. Because the Jobo solution volume is so low and aeriates the developer, Kodak recommends 1 shot and toss. Same recommendation goes for bleach and fixer. I replenish the Bleach seems wasteful not to. Fixer I use twice then toss. Because you wash the film after fixing no stabilizer is needed, just a final rinse SM solution, I mix with purified water and use for many rolls. The RA system requires 1 minute bleach and I fix for a couple minutes. I rinse between bleach and fixer just to prevent carry over. Best Regards Mike
Ever since I have been developing C41 my method has not changed. That is over nearly 30 years ago. The chemistry I use has varied over the years, starting out with Agfa, then Tetenal, Fuji, Digibase and now back to Tetenal. I have always used the same quantities, 160cc for 25mm and 250 for 120 (Or 2 x 35mm). I can count the number of failures on half of one hand with a finger left over.

I NEVER pre-rinse on the basis that once water is introduced into the tank, you will never get rid of it all, so what is left may dilute the developer. The developer is set to heat to 101F or 38.5c. I find this improves saturation slightly, but also may be that I am compensation for a slightly inaccurate thermometer. (Mercury type)

I pre-heat by loading the film into the tank and immersing it fully into the waterbath of my JOBO when the water is still cold and leaving it there until the waterbath is up to operating temperature. That way it ensures the pre heat is even and consistent. Only with 120 film do I give a further 5 mins dry rotation at 101F(38.5c) before filling the tank with the developer.

The bleach and fix are always extended by 1 minute 'just in case' The wash/rinse stages are by 6 x 30 second stages. Then, as in my previous post immediately before this one, This is followed by 2 minutes immersion in a stabilizing bath with no agitation. The films are then removed from the spiral and hung up in an area where there will be a small circulation of moving air until dry.

Purists will wince when I tell you this is from hooks on the top of door frame of a room adjacent to my darkroom, but I never ever have had a problem with dust or drying marks. If it works for me it should work for anyone else.

Last edited by John King; 13th September 2018 at 06:51 AM.
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