Minimum Quantity of Perceptol Needed

This topic has already become an off-shoot to the thread on Adox CMS20 and Perceptol and so to avoid exacerbating further extraneous content there I thought it best to start another thread.

After some thought I felt in the back of my mind that there had been a long discussion of this subject of Perceptol minimum qunatity on FADU, another analogue site with mainly but not exclusively a UK based membership and so it proved to be the case. In fact it had prompted me to write to Ilford in May 2016 and ask the question. I had received a reply from David Abberley of Ilford/Pemberstone at that time which I summarise below:

Ilford had based its literature on a minimum of 70mls of stock Perceptol per film so at 1+3 a tank for a 135 film needed have a capacity of 280mls. Most tanks with the exception of Durst and Jobo(250mls only) meet this requirement. Paterson tanks for instance are 300mls so 75mls stock can be used
Of course 120 tanks will need more liquid that this but at 1+3 will easily exceed the minimum quantity of stock Perceptol.
I have had success in my terms with about 63mls of Perceptol in Jobo and Durst tanks but this, in Ilford's view, is getting very close to the absolute minimum and may pose exhaustion dangers

So that was Ilford's answer to my query in May 2016

I appreciate that others here may be uncomfortable with less than 100/150/200/250 mls of stock and may feel that success in their books requires higher than 70mls of Perceptol stock. It is of course their decision

I just thought it worthwhile to put before Photrio what Ilford had.

pentaxuser

Pentaxuser, you already know my answer but I repeat it here.

The Ilford PDF datasheet for Perceptol defines a capacity of 4 films (135 or 120) per litre. However, on the inside of (older) boxes a number of 5 films is mentioned, so I asked Ilford (Harman Technical UK) on 15/11/17 what the exact value was and I got the following answer:

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Good afternoon Billy Axeman,

I'm so sorry that you have found conflicting information - I appreciate its left you confused as to which is safe/correct.

If you are ever in doubt re anything/see conflicting info as that in the future, my advice would always be to go by whats on our website as opposed to the cartons - because website errors tend to be swiftly corrected, whereas carton artwork updates can take several months to get through stocks / be corrected.

But to help clarify all for you now - the technical information sheet number is the correct version - it is 4 films 35mm/120 films per litre.
That is says 5 x 35mm/120 films on the chemistry carton interior - is incorrect.
To be honest - if you had put 5 films through, its likely you would not really have detected any obvious deterioration. Its more if you started to put say 6 plus films through - you would.

I think the reason you are seeing the conflicting info - is because your 93E batch of Perceptol is now quite old. It was made June 2012. It looks like although the artwork at that time was incorrect, all has since been corrected - as my checking current carton artwork seems to now correctly show it as 4 films per litre (exact as on the website).

I hope all now makes sense for you, and you can get some pleasing results with your films

Kind regards,

Sue Evans
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So, when you can develop a maximum of 4 films from one litre of stock you need 1000/4=250 ml stock per film, not less. When you dilute 1+1 you need a tank with a volume of 500 ml, when you dilute 1+3 you need a tank with a volume of 1000 ml. Higher dilutions are not recommended by Ilford.

Regards

michael_r said:

Billy Axeman,

The indication of 4 films/liter in the PDF datasheet is for developer that is being reused (ie used developer poured back into stock bottle and mixed with unused developer). Capacity would be considerably higher when the developer is used one-shot.

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That is a very interesting observation, I never read it that way.
So, that would give us at least a capacity of 1000/70=14 films.

Why isn't Ilford telling us that. A minimum volume of 70 ml stock / film is also nowhere mentioned in the datasheet.

I have checked my box again and the info on the inside is even more misleading. They clearly say that the capacity is 4 films independently if you are reusing or not. For reuse they repeat 4 films, but include the percentages for increasing developing time.

I'm still not convinced. I'm going to ask Ilford again what they have to say about that, with a link to this thread.

Billy Axeman said:

That is a very interesting observation, I never read it that way.
So, that would give us at least a capacity of 1000/70=14 films.

Why isn't Ilford telling us that. A minimum volume of 70 ml stock / film is also nowhere mentioned in the datasheet.

I have checked my box again and the info on the inside is even more misleading. They clearly say that the capacity is 4 films independently if you are reusing or not. For reuse they repeat 4 films, but include the percentages for increasing developing time.

I'm still not convinced. I'm going to ask Ilford again what they have to say about that, with a link to this thread.

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Yes i think michael is right and the instructions on the box are wrong as they dont actually make any sense regarding reusing the developer. I think it should say 4 times as many films rather than 4 films. Thats how ive always decided to decipher it anyway

I have just sent a mail to Harman Technical Services about this and I hope to get an answer at the end of the week.

The purpose of Perceptol is to get a reduced grain. So the next question is, what is the influence of a dilution (70 ml stock in a 250 ml tank is about 1+3). It was my understanding that a stock solution gave the least amount of grain. Is that correct?

Billy Axeman said:

I have just sent a mail to Harman Technical Services about this and I hope to get an answer at the end of the week.

The purpose of Perceptol is to get a reduced grain. So the next question is, what is the influence of a dilution (70 ml stock in a 250 ml tank is about 1+3). It was my understanding that a stock solution gave the least amount of grain. Is that correct?

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Yes, all things the same, using Perceptol full strength will give the least grain/smaller grain. That's because it has the highest concentration of grain dissolving Sodium Sulfite. When you dilute Perceptol you are also diluting the concentration of Sodium Sulfite, which means less dissolving power. JohnW

John Wiegerink said:

Yes, all things the same, using Perceptol full strength will give the least grain/smaller grain. That's because it has the highest concentration of grain dissolving Sodium Sulfite. When you dilute Perceptol you are also diluting the concentration of Sodium Sulfite, which means less dissolving power. JohnW

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Thanks John, good to know.
This is also a theme Ilford is saying nothing about, as far as I know.

All I can say Billy is that I asked the direct question of what is the minimum amount of Perceptol stock needed to successfully develop a roll of film be that 135 or 120. both of which have roughly the same surface area, and what I have reported here is what the reply said.

My contact, as I reported, was someone called David Abberley.

pentaxuser

I also think that 4 films per litre may refer to the stock solution re-used, not to Perceptol as a diluted one-shot developer. Older Ilford literature mentions 100 ml or even 70 ml as the minimum amount.

the box gives time compensation for reuse for up to 10 films

Craig75 said:

the box gives time compensation for reuse for up to 10 films

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There is conflicting info on the inside of the box and Ilford recommends using the PDF from the web site because that is the most recent version. See my post #3. In the PDF the table shows NR (not recommended) for film N=5 and higher (page 8). So, that is consistent with a capacity of 4 films.

Billy Axeman said:

There is conflicting info on the inside of the box and Ilford recommends using the PDF from the web site because that is the most recent version. See my post #3. In the PDF the table shows NR (not recommended) for film N=5 and higher (page 8). So, that is consistent with a capacity of 4 films.

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doh.

So there is absolutely no point reusing it and you may as well use it as 4 separate 250ml one shots keeping the same time rather than pouring used solution back into stock and adjusting time?

pentaxuser said:

All I can say Billy is that I asked the direct question of what is the minimum amount of Perceptol stock needed to successfully develop a roll of film be that 135 or 120. both of which have roughly the same surface area, and what I have reported here is what the reply said.
My contact, as I reported, was someone called David Abberley.
pentaxuser

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This is a useful thread pentaxuser to get things straight.

It is quite possible I will get the same answer as you got. I have had other contacts with Harman in 2017 and until now my mails are answered by Sue Evans.
Any answer is good actually, the only thing I want to know is how to proceed in a correct way for consistent results.

Deleted - Double post.

Craig75 said:

doh.

So there is absolutely no point reusing it and you may as well use it as 4 separate 250ml one shots keeping the same time rather than pouring used solution back into stock and adjusting time?

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Exactly, if you have the choice you are doing single shot stock of course. But that's only for a tank of 250 ml (or a multiple), otherwise you must reuse. I agree it is strange so I'm curious what Ilford will say.

Billy Axeman said:

This is a useful thread pentaxuser to get things straight.

It is quite possible I will get the same answer as you got. I have had other contacts with Harman in 2017 and until now my mails are answered by Sue Evans.
Any answer is good actually, the only thing I want to know is how to proceed in a correct way for consistent results.

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I look forward to your reply from Ilford, Billy. Hopefully Ilford will address the key issue which is you needing to know the minimum quantity of stock Perceptol per film .

pentaxuser

Perceptol, like many metol-based developers, has the capacity to reliably (that is, without variable outcomes irrespective of scene content) process 80 square inches of film only when at least 250ml of stock solution is used. I don't care what inconsistent answers might have been provided by different correspondents at HARMAN before and after its ownership changed. I've done the work. Two identical large sheets of film, developed one-shot at the same temperature, for the same length of time, using the same agitation, gave much lower density when only 187.5ml of Perceptol concentrate per 80 square inches was used than when 250ml was.

If a scene is predominantly low values, meaning a negative of it would be more clear than dark, less developing agent might not have bad consequences. However, should the scene be predominantly high values, meaning a negative of it would be more dark than clear, scrimping on the 250ml stock solution requirement would almost certainly result in lower than desired/expected densities. It's a straightforward choice between control or crap shoot.

Billy Axeman said:

...The purpose of Perceptol is to get a reduced grain...

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That's its primary purpose. The reason I use it is because it requires the longest development time of any commercially available developer that's readily available to me. Thus, when ambient air and water temperatures are high here in summer, rotary development times are still sufficiently long to ensure even results.

michael_r said:

...in my own controlled experiments I found no difference in density between 200ml and 400ml stock...

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Unless those experiments included very high-key scenes that fully taxed the developer's active ingredient, they probably wouldn't have revealed the inadequacy of 200ml.

michael_r said:

...As an aside, David Abberley worked/works at Ilford before/after the ownership change.

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The inconsistent information is not related to any one person. Posts #1 and #3 cite different people as well as printed documentation.

I'll rely on the long-known minimum quantity of metol-based developer stock solution required, confirmed by my own test, rather than varying claims popping up on line. Others may feel free to shoot craps with their own film.

Just as a matter of interest, did anyone ever make a 1L developing tank tank to allow a 1+3 dilution with what some believe is the minimum amount of stock needed? Is this 250ml the minimum for one film and if it is, does that mean that anyone wanting to develop 2x 135 films at 1+3 together, needs a 2L tank and was a 2L tank ever made?

Thanks

pentaxuser

pentaxuser said:

Just as a matter of interest, did anyone ever make a 1L developing tank tank to allow a 1+3 dilution with what some believe is the minimum amount of stock needed? Is this 250ml the minimum for one film and if it is, does that mean that anyone wanting to develop 2x 135 films at 1+3 together, needs a 2L tank and was a 2L tank ever made?

Thanks
pentaxuser

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Jobo has a tankmodule 1530 for extending the standard 1510 tank (250 ml) or the 1520 tank (485 ml). The extension module 1530 is 725 ml. It comes with a central rod, but no wheels.

They have also a 1540 tank which looks like a combination of 1510 and 1530 (975 ml).
Theoretically you can add two extensions to a standard tank, but that is a very long and thin combination.

Edit 1 - They also have a 2500 tank system for 135 and 120 films. It looks bigger but I don't know the volumes.
Edit 2 - Don't worry, it's all whipped up. Or revert to 1+1 or stock.

Thanks Billy. So while a combination of Jobo tanks gets you close to 1L, it sounds as if it makes the tank a bit difficult to use. No-one, it seems, ever made a single custom-made tank for 1L let alone a tank for 2L so just on those grounds I do wonder if Perceptol was actually designed for 250ml as a minimum level of stock. It would seem that if a 1L tank is needed then no tank manufacturer ever tried to design a tank for it.This being the case and Ilford knowing this to be the case, it just seems strange that Ilford did not and does not warn users that if they desire to use Perceptol at 1+3 they need to find a means of finding a 1L tank and a 2L tank if they want to do 2x 135 films together.

This is just me thinking out aloud as they say

pentaxuser

Well, my take is that if you use Perceptol it's for reducing grain. And you will get the smallest grain with stock solution. So, that can be done in a small tank.

Michael, do you know any developer which has a different capacity for reuse and for single-shot?

pentaxuser said:

...Is this 250ml the minimum for one film...

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It's for 80 square inches of film. That's one roll of 36-exposure 35mm, one roll of 120, four sheets of 4x5, one sheet of 8x10, etc. My test was performed using 500ml and 375ml of Perceptol stock on two identically exposed sheets of 11x14 film.

Thanks Sal. I believe you are confirming that in your experience 250ml of Perceptol is needed for a roll of film and this is indeed what you had said quite articulately in an earlier post. Billy has give one explanation as to why there is no 1 or 2L tanks, namely that Ilford never meant Perceptol to be used at any dilution so the question of why there are no big tanks such as 1L or 2L does not arise.

Yet Ilford mentions dilutions of 1+1 and 1+3 but based on Billy's explanation I'd have thought that if 1L of liquid is needed for its 1+3 dilution then Ilford would chose to recognise that no tank exists and to at least say that as Perceptol is designed for maximum fine grain then it recognises you are on your own if you choose to use its 1+3 dilution.

In fact knowing that a normal tank is say 300mm and that Perceptol is designed for max fine grain and any dilution is sub optimal, I wonder why it even gives other dilutions when this leads to frustration on the part of users because (a) the outcome is sub optimal and (b) there is no tank available.

My only desire was to share with Perceptol users what Ilford had said to me in direct reply to the direct question of what is the minimum amount of stock needed and then pose questions which stem from the consequences of it being necessary, allegedly, to use 250ml of stock.

If users wish to use 250ml of Perceptol stock each time then that is fine by me but if they would like to use less and still get successfully developed film then I felt I owed it to them to say what Ilford had said, namely 70ml was the minimum needed. Most people want to get value for money and film enthusiasts probably belong to the "most people" group so do not want to spend more than is necessary. I certainly belong to that group seeking value for money.

On the basis of 250ml minimum, that is only 4 films per litre packet and that must make Perceptol top or nearly top of the league in terms of price per film. It way exceeds what Xtol costs for instance. At that price it has to be so much better than other developers to justify the cost, doesn't it? Secondly I find it strange that if you only get 4 films per 1L packet, why Ilford does not supply a 5L or even 10L packet. Most other developers in their designated containers will normally process more than 4 films and 5L would at least process 20

pentaxuser