Jobo with pre-rinse - reduced development time?

Doc W · Apr 12, 2017

I will be using home-brew Perceptol in my Jobo and Ilford says to reduce the developing time by up to 15% in a rotary processor. What about for pre-rinse? I use a pre-rinse with my Jobo simply because Jobo recommends it (I don't use a pre-rinse with inversion tanks just so I can be on both sides of the perennial pre-rinse debate). How much does a pre-rinse reduce developing time, if at all?

Leigh B · Apr 12, 2017

Pre-rinse has no bearing whatsoever on development time.

Development time is reduced in a rotary processor due to the continuous "agitation".

- Leigh

pentaxuser · Apr 12, 2017

The general( note, not absolute) view seems to be that a 5 minute pre-soak keeps the times for rotary the same as for inversion. This appears to be backed up by many users but not all. In "The Rotary Processor Manual" by John Tinsley, a much sought-after book, he says that his experience with a range of Ilford films such as PanF, FP4+ and Delta 400 is that the times remain the same with a 5 minute pre-soak. The theory seems to be that the pre-soak compensates for the effect of rotary processing

However you might like to look at the article in the Unblinkingeye website where the effect of rotary processing on times compared to inversion seems to vary depending on the film.

pentaxuser

Doc W · Apr 12, 2017

Leigh, I am not saying the rinse affects actual development. I am assuming that the soaking of the film before development allows the developer to penetrate the film more quickly (or slowly?) and thus has an impact on the development time.

Leigh B · Apr 12, 2017

Doc W said:
I am assuming that the soaking of the film before development allows the developer to penetrate the film more quickly (or slowly?) and thus has an impact on the development time.

Interesting thought, but...

With a wet emulsion, the developer must displace the water in order to penetrate the emulsion.

With a dry emulsion, the developer just soaks in unimpeded.

pentaxuser said:
The general( note, not absolute) view seems to be that a 5 minute pre-soak keeps the times for rotary the same as for inversion.

That suggests that the pre-rinse retards development, as perhaps explained above.

- Leigh

Photo Engineer · Apr 12, 2017

I use a 1 - 2 minute prewet and do not change development times for color or B&W. I have done that for years with no problems.

PE

TheFlyingCamera · Apr 12, 2017

Another 2 minute pre-wet processor here, and I keep my times the same for the Jobo as for manual agitation.

Alan9940 · Apr 12, 2017

I always do a 5 minute pre-rinse when processing on my CPP2 with 2500 series and Expert Drum. However, my tested development times have always come out shorter than inversion times I see on the Massive Dev Chart.

BMbikerider · Apr 12, 2017

I would have thought the last two are closer to the mark. Using a pre-rinse would slightly dilute the developer so necessitating a slightly longer time. (about 10 seconds)

I have always found a pre-rinse is not required - unless the water is exceptionally 'hard'. When I lived south of London where the water was hard, all I did was add a couple of drops of wetting agent. It is all to do with breaking down the surface tension and getting the developer to flow evenly over the film.

grahamp · Apr 12, 2017

The pre-rinse will do two things - saturate the film and stabilize the temperature of the film and drum. It may also clear the anti-halation dye. Gelatin does expand when wet, so the permeability of the gelatin should increase, though the developer has to diffuse into the water in the emulsion. That should be a shade faster than starting with dry film.

I used a pre-rinse with a single-shot developer. I don't do it with a re-usable developer like Thornton Two Bath, as the dilution effect could be a problem. But a little time adjustment is easy to do.

One should sanity check the times in the Massive Dev Chart for your own conditions.

Sirius Glass · Apr 12, 2017

Prewetting will not change the developing time.

Vaughn · Apr 13, 2017

Leigh B said:
...With a wet emulsion, the developer must displace the water in order to penetrate the emulsion...- Leigh

Just a thought while listening to a live version of "Wish You Were Here", but does the developer 'displace' the water in the swelled gleatin...or...does the water in the gelatin speed up the entry of developing chemicals deep into the emulsion due to the action of osmosis?

StoneNYC · Apr 13, 2017

Alan9940 said:
I always do a 5 minute pre-rinse when processing on my CPP2 with 2500 series and Expert Drum. However, my tested development times have always come out shorter than inversion times I see on the Massive Dev Chart.

Although my experience is anecdotal, I also will concur that my experience has been the same.

BMbikerider · Apr 13, 2017

Well all or most seem to be in favour, but I take as I find. I have never ever even considered pre-rinse, not even for colour negative. If it is so essential, why is it not promoted by the mainstream film manufacturers? Hmmmmm? Some may do but I cannot remember seeing this recommendation by Ilford, Kodak or Fuji.

To stabilise the temperature inside the tank, I have as long as I can remember, placed the tank in water for the whole time the water in my JOBO is heating up from cold. Before that I was guided by the developer manufacturers with their times and if the ambient temperature is below normal, their suggestion was always to heat the developer up by a two or three degrees 'F' more than they suggest.

In all, I think I can count my development failures on my fingers, (with some left over) which isn't bad for over 55 years of darkroom work.

Down Under · Apr 13, 2017

A great deal has been written on this topic. Some of it very confusing to a darkroom worker like me, dedicated as I have always been to the KISS principle in my D&P.

You can easily and simply resolve this to satisfy yourself. Sacrifice one roll of your favorite 120 film (or a partial roll of 35mm). Shoot 12-16 exposures of the same scene at the same exposure, to ensure consistency.

Cut the film into two lengths. Process the first length with a 1-2 minute presoak, and the second length without the presoak. Compare the results.

If feeling particularly obsessive about all this, you can then repeat this experiment with a 10% or 15% reduction in developing time.

I did this testing regularly for a long time, with every new film I bought. Eventually I realised that with only two exceptions, there were no variations whatsoever in the prewet and not prewet films. The two exceptions were Fuji Acros and Ilford Pan F, which I have long regarded as "difficult" emulsions anyway.

Try this and you will then be satisfied with your own tested results, not someone else's developing charts.

I now use mostly D76 and Xtol, but I was a dedicated user of Thornton's Two Bath (the Ansel version) for many years, which by and large is not recommended for rotary processing. I did it very happily with my Dobo Duolabs for a long time, and found that adding 60-90 seconds to the developing time kicked up the shadow and mid tones contrast nicely. Unlike many others, I did not have any problems with "bromide drag" from the constant rotating. Others' mileage may differ in this. Those who would disagree, please let us know (and please tell us why).

Doc W · Apr 13, 2017

Photo Engineer said:
I use a 1 - 2 minute prewet and do not change development times for color or B&W. I have done that for years with no problems.

PE

PE, are you saying that the rotary processor development time will be the same as the inversion method time, if you use a pre-rinse in the Jobo?

Photo Engineer · Apr 13, 2017

Yes, times are the same. However, the prewet is recommended by Jobo and for all rotary processes it is advised. And, there is no change in time that I can see.

PE

klownshed · Apr 13, 2017

BMbikerider said:
If it is so essential, why is it not promoted by the mainstream film manufacturers? Hmmmmm? Some may do but I cannot remember seeing this recommendation by Ilford, Kodak or Fuji.

In my case it's because I first followed ilfords recommendations when using my Jobo and reducing development time by 15% and ended up with over development.

I then found a Jobo manual that recommended a 5 minute pre wash and no time difference from the inversion times for B&W film.

So I tried Jobo's method and it worked. Perfectly. With every combination of film and developer I have tried.

I guess Jobo know more about developing film in their machines than the film manufacturers do.

But just do what works for you. If you have a method and it works, there's no need to change it. I'm not suggesting anybody should do what I do, I'm just saying it works for me.

If there's one area I don't want to experiment too much it's in film developing. All I want from my developing routine is something that works consistently without mucking about. Others seem to enjoy experimenting with film developing, which is fine, but once I've got a method that works for me that's it, I'm happy.

Petraio Prime · Apr 13, 2017

Leigh B said:
Pre-rinse has no bearing whatsoever on development time.

Development time is reduced in a rotary processor due to the continuous "agitation".

- Leigh

This is correct!

Jobo with pre-rinse - reduced development time?

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