Development time rotary vs. inversions (Tetenal Rapid C41)

[michaelbothager]

Hello all.

The instructions for Tetenal Colortec C-41 Rapid Negative Kit states times for continuously rotary processing. If doing inversions (4 every 30 seconds), do the development times need to be extended? It is, as I understand it, necessary to reduce development time when going from inversions to cont. rotation.

If the times needs to be extended, then by how much? And I assume that the extended times is for both dev, blix and stab.

Anyone who have any knowledge or experience to share?



Rgds
Michael

 

[miha]

I'm doing inversions, but I'm agitiating for the whole time which is 3 mins 15 seconds. Why would you want to do 4 inversions every 30 seconds only?

 

[michaelbothager]

I'm doing inversions, but I'm agitiating for the whole time which is 3 mins 15 seconds. Why would you want to do 4 inversions every 30 seconds only?

Well, based on what I've read/seen on the net, thats how many people do it. Also, it would be consistent with my method of development.

I guess you rotate with the tank in a water-bath to keep the temperature up?

 

[miha]

Well, based on what I've read/seen on the net, thats how many people do it. Also, it would be consistent with my method of development.

I guess you rotate with the tank in a water-bath to keep the temperature up?

Not really. I start with 39C so that I allow for a little drift. Or I put the tank under a hot water for a moment. I'm using stainless steel tanks btw.

 

[michaelbothager]

Not really. I start with 39C so that I allow for a little drift. Or I put the tank under a hot water for a moment. I'm using stainless steel tanks btw.

OK, thanks for your answer.

Rgds
Michael

 

[RPC]

The standard development time for C-41 is 3 minutes, 15 seconds. You should not deviate from this unless reusing the developer. If you are using inversion with small tanks, see Kodak publication CIS-211 for proper technique. I would not agitate continuously or you will over develop the film.

Edit: Here is a link:

http://125px.com/docs/chemicals/kodak/cis211-Flexicolor_in_small_tank.pdf

 

[Mick Fagan]

I've developed C41 in small tanks using inversion, where I invert for the first 10 seconds, then at every 30 second interval for 10 seconds (three inversions). I've also developed C41 in rotary processing (Jobo) where the film is under constant agitation. To be honest I have not seen a difference. This includes using Kodak C41 control strips, which are the industry standard.

C41 is a very robust standard, whether you are talking about the film or the process itself. That is my take anyway after years and literally thousands of C41 rolls processed. If you can keep your tank at or around 37.7ºC temperature and process for 3'15" you should be very happy with your results.

Mick.

 

[RPC]

Intermittent agitation can be done successfully with different schemes, as long as the overall development is the same. But I can tell you that using continuous inversion agitation with a tank, which is different than a rotary processor, will give results quite different than intermittent agitation, and no doubt out of spec.

I use an inversion agitation scheme a little different than Kodak's, (one inversion every 10 seconds) but get sensitometrically good results. Until beginners determine an alternate scheme that gives acceptable results, I would recommend they start with Kodak's scheme.

 

[thuggins]

I've done Tetenal E-6 by both constant rotation and inversion, using the same time for both and the results look the same. In my experience agitation is not that critical, as long as you are doing some kind of agitation.

 

[RPC]

I have done both too and gotten different sensitometric results. The differences may not be noticeable, however, depending on subject matter, even if out of spec.
Nonetheless I use an agitation scheme I have found gives me the best sensitometric results.

 

[michaelbothager]

Nonetheless I use an agitation scheme I have found gives me the best sensitometric results.

Maybe you can describe what scheme you use?

 

[RPC]

One inversion at the start and then every 10 seconds throughout the cycle, keeping the tank immersed in the water bath when not inverting. I also rotate about a quarter of a turn after each inversion.

 

[michaelbothager]

One inversion at the start and then every 10 seconds throughout the cycle, keeping the tank immersed in the water bath when not inverting. I also rotate about a quarter of a turn after each inversion.

Thank you. I'll try that.

 

[pentaxuser]

Can

Intermittent agitation can be done successfully with different schemes, as long as the overall development is the same. But I can tell you that using continuous inversion agitation with a tank, which is different than a rotary processor, will give results quite different than intermittent agitation, and no doubt out of spec.

I use an inversion agitation scheme a little different than Kodak's, (one inversion every 10 seconds) but get sensitometrically good results. Until beginners determine an alternate scheme that gives acceptable results, I would recommend they start with Kodak's scheme.

Can you say why continuous inversion agitation differs from continuous rotary agitation in terms of results? As each ensures that developer is continuously passed over the film's surface then intuitively it leads you to believe that each method should have the same results. It may be related to the fact that rotary agitation uses just over half the developer that inversion needs so not all of the film is continuously immersed but this is just speculation on my part.

Ilford for instance recommends that rotary agitation should be about 15% lessfor trad B&W so it appears that in trad B&W, less developer which doesn't cover the film at all times, isn't balanced exactly in time as in the C41 process intermittent inversion process where it remains at 3' 15" irrespective of the agitation regime.

Thanks

pentaxuser

 

[RPC]

Can you say why continuous inversion agitation differs from continuous rotary agitation in terms of results? As each ensures that developer is continuously passed over the film's surface then intuitively it leads you to believe that each method should have the same results.

In a tank the developer is in constant contact with the emulsion, and I have to believe the velocity of the developer across the surface of the emulsion is much higher during inversions than during agitation with a rotary processor so continuously inverting would cause a higher degree of development, with more development in the upper layers.

It may be related to the fact that rotary agitation uses just over half the developer that inversion needs so not all of the film is continuously immersed but this is just speculation on my part.

I have not used rotary processors so am not completely familiar with their operation. Everyone seems to call it "continuous agitation" but unless the processing tube is full, it seems to me there would be a time during rotation when the developer is motionless in the emulsion, i.e., in the upper part of the tube, then the film would pick up fresh developer on its downward rotation, and that is when agitation would actually occur. I have used print drums and that is what happens there, and so I never thought of drums as having continuous agitation. If rotary film processors do not operate like that, someone please enlighten me.

 

[pentaxuser]

Thanks for the reply RPC. I have a Jobo rotary processor. It turns the tank and thus the reel 3 times in one direction then 3 times in the opposite direction. I can't look inside the tank of course but given the weight of the liquid and gravity, what I imagine happens is that the reel moves and the liquid stays relatively static although I imagine there will be something of a wave effect.

Certainly continuous inversion agitation creates a different pattern of liquid movement but if the tank is full as it has to be for inversion agitation then I'd have thought that there might not be as much liquid movement during inversion agitation as there is during rotary agitation.

I suppose the only way to be sure that your different sensitometric results are statistically valid would be to carry them out on numerous occasions while being sure of isolating any other variables. How big were the differences and what were the practical consequences in terms of colour rendition etc?

I accept that if Kodak does not recommend continuous inversion agitation there must be a reason but could it be as simple a reason as trying to offer enthusiasts the easiest method consistent with correct development?.

miha for instance uses continuous inversion agitation and presumably gets satisfactory results.

We might need PE to contribute his knowledge here

pentaxuser

 

[RPC]

To me, it just stands to reason that if a certain intermittent agitation will give correct results, then continuous agitation would cause excessive development as I have observed. Whatever happens during each type of development, it will be affected by changing the rate. As I understand it, changing the speed of a rotary processor can affect sensitometric results. So it comes as no surprise to me that the same will happen with inversion. Kodak's literature says agitation can affect control strip plots. Color film is multilayered and the top layer is affected the most with changed agitation, and crossover can result. As with low temperature color processing, whether this is acceptable is up to the user (although the affects of different agitation schemes will likely not be as much as low temperatures).

I would imagine Kodak did not design the C-41 process using continuous agitation always be used because they realized that different types of processing equipment would be used to develop film, and each would require its own agitation scheme to give optimum results.

 

[pentaxuser]

Thanks for the reply. So what actual differences did you see in the two sets of negatives and how did this affect the prints from the different sets of negs?

pentaxuser

 

[Mick Fagan]

I would imagine Kodak did not design the C-41 process using continuous agitation always be used because they realized that different types of processing equipment would be used to develop film, and each would require its own agitation scheme to give optimum results.

I had a think about this, maybe, maybe not.

The vast majority of C41 machines were minilabs, which by the virtue of the fact that the film was continuously being pulled through each and every bath, with every bath having a pump constantly circulating chemistry, which to me, infers constant agitation. Something I hadn’t thought of before.

The dip N dunk machines we had at the lab I worked at, gave nitrogen bursts every 10 seconds, effectively constant agitation.

Kodak Australasia had pretty much the biggest C41 processor in the country, on throughput; it only processed 35mm format. Customer’s films were sent via post, courier or mail to the processing factory. Once there, they were numbered with sequentially numbered stickers, then these films were, in total darkness, placed end to end on a 1,000ft (304.8m) movie type reel; blind people did this job.

From there, the films were threaded into a long processing machine at one end then onto another reel at the end of the processor. In effect, they were in constant movement. Sort of means constant agitation, more so as the processor was constantly pumping the chemistry and chemistry was also being constantly replenished. You should have seen the size of the replenishment tanks.

C41 is the shortest processing time of any normal film process that I know of. It is extremely robust and can be abused, but for optimal results it does require a couple of things. Timing should adhere as close as possible, to 3’15”, temperature should be as close as possible to 37.7ºC.

If you keep these two about right and use one shot processing, then, if your experience is anything like mine, Kodak C41 control strips will match Kodak data almost perfectly, something even my professional lab didn’t believe would happen.

I must admit I had never before thought C41 could have, or even may be a continuous agitation process simply by default of the machinery processing it.

Thoughts?

Mick.

 

[MattKing]

Mick:
I've always thought of commercial processing as being a continuous agitation process.
With a development time of 3'15", I had always assumed that the developer was fast and very active. That pretty well requires a lot of agitation.
It seems to me that longer development times would reveal much more variability as a result of varying the agitation regime.

 

[RPC]

Thanks for the reply. So what actual differences did you see in the two sets of negatives and how did this affect the prints from the different sets of negs?

pentaxuser

It was many years ago but remember I got higher density and contrast, mostly in the yellow (blue sensitive, topmost) layer with the higher agitation. I didn't bother to print them, but I knew from experience I would see it in the gray scales. With my usual agitation I got parallel, normal looking curves.

 

[RPC]

I was aware commercial processors generally use continuous agitation but as I said in an earlier post the actual agitation scheme doesn't really matter as long as overall development is the same. A commercial processor would be designed to have the speed the film moves through the developer and developer flow adjusted for optimum results. For inversion, the rate of optimum development is adjusted by an inversion scheme and a rotary processor would have its own speed for optimum. While the time and temperature are fixed, each method requires an agitation adjustment for optimum results.