Stopping Prints Before Fixing with Tf-5 without running water

faberryman · Jun 23, 2023

The instructions for Kodak Indicator Stop Bath call for a 63:1 dilution. Presumably Kodak did not just pull that number out of the air, but maybe I give them too much credit. For those of you who use a more dilute solution, how did you determine that a more dilute solution was adequate? What is your motivation for using a more dilute solution? Is is to lesser the odor? Is it to save money? Something else?

BHuij · Jun 23, 2023

My line of reasoning is that I want to keep my TF-5 as close to neutral pH as possible. Its strong concentration and near neutral pH are what make it capable of very quickly and effectively fixing a print completely, and then rinsing out quickly as well. While it sounds like it's buffered enough that some residual developer and/or acidic stop bath won't be causing wild pH swings anyway, I've been getting away with plain old water stop with no measurable or observable problems for over a year, even with fiber paper. Not only that, but my water is itself somewhat alkaline (pH of about 8.1 out of the tap). So introducing even a significantly less concentrated acidic stop bath is, I think, balancing the scales of pH on either side of 7 better than plain water, and there's no need to use full-strength acid bath.

All of this is very much armchair chemistry, and I suspect it's not going to have much of an effect on anything anyway. So I guess at the end of the day, I'm doing it because I think it's theoretically a bit better for my workflow than using either plain water stop or full-strength 1:63 stop, and even if I'm wrong it's probably no big deal one way or the other.

MattKing · Jun 23, 2023

faberryman said:
The instructions for Kodak Indicator Stop Bath call for a 63:1 dilution. Presumably Kodak did not just pull that number out of the air, but maybe I give them too much credit.

The 63:1 is a natural target - the one pint bottle of concentrate mixes up to exactly to eight US gallons of working solution - a useful volume for your average, US based deep tank commercial processing line .
The majority of historic Kodak packaging was sized for US units - the switch to metric was one of the revolutionary aspects of X-Tol.

koraks · Jun 23, 2023

BHuij said:
Not only that, but my water is itself somewhat alkaline (pH of about 8.1 out of the tap)

But it's virtually unbuffered. This makes its pH virtually irrelevant. Any pinch of whatever will totally dominate whatever tiny amount of something is causing your water's pH to not be precisely 7.

faberryman · Jun 23, 2023

MattKing said:
The 63:1 is a natural target - the one pint bottle of concentrate mixes up to exactly to eight US gallons of working solution - a useful volume for your average, US based deep tank commercial processing line .
The majority of historic Kodak packaging was sized for US units - the switch to metric was one of the revolutionary aspects of X-Tol.

So why not choose 126:1 and then a half pint bottle would mix up exactly eight gallons of working solution?

MattKing · Jun 23, 2023

faberryman said:
So why not choose 126:1 and then a half pint bottle would mix up exactly eight gallons of working solution?

I'm not sure that one could - at least not safely.
As it is, that 63:1 concentrate is strong enough to discolour a laminate countertop if you spill it and don't clean it up quickly, and it smells really, really strong - throat catching strong.

Sirius Glass · Jun 23, 2023

faberryman said:
The instructions for Kodak Indicator Stop Bath call for a 63:1 dilution. Presumably Kodak did not just pull that number out of the air, but maybe I give them too much credit. For those of you who use a more dilute solution, how did you determine that a more dilute solution was adequate? What is your motivation for using a more dilute solution? Is is to lesser the odor? Is it to save money? Something else?

What is wrong with RTFM and following directions? Is it really all that hard? We all know that people dilute Kodak Stop Bath With Indicator because it is just so damned expensive!

john_s · Jun 23, 2023

The concentration has an effect on working life/capacity. I am not a very productive darkroom worker so a dilute SB doesn't get anywhere near exhausted. I toss it at the end of a session, so it's less wasteful to use it dilute.

faberryman · Jun 23, 2023

MattKing said:
I'm not sure that one could - at least not safely.
As it is, that 63:1 concentrate is strong enough to discolour a laminate countertop if you spill it and don't clean it up quickly, and it smells really, really strong - throat catching strong.

Sirius Glass said:
What is wrong with RTFM and following directions? Is it really all that hard? We all know that people dilute Kodak Stop Bath With Indicator because it is just so damned expensive!

I was suggesting to Matt that the reason Kodak recommending 63:1 dilution was more than simply because a pint made eight gallons of working solution which would fill a US deep tank commercial processing line.

MattKing · Jun 23, 2023

faberryman said:
I was suggesting to Matt that the reason Kodak recommending 63:1 dilution was more than simply because a pint made eight gallons of working solution which would fill a US deep tank commercial processing line.

I'm sure Kodak started first with four criteria - typical volumes for working strength stop bath, appropriate dilution for working strength stop bath, safe and economical concentrations for the concentrate and convenient and useful package size for the bottle.
The final numbers - and the mix dilution chosen to go from concentrate to working solution - were influenced by the measurement system used - ounces, pints, quarts and gallons (all US). There are 8 US pints in a US gallon - thus the factor of 8x8=64 (63:1).
A European centred manufacturer would have been much more likely to end up with metric friendly relationships - 500 ml to make 10 litres being the choice made by modern Ilford.

faberryman · Jun 23, 2023

MattKing said:
I'm sure Kodak started first with four criteria - typical volumes for working strength stop bath, appropriate dilution for working strength stop bath, safe and economical concentrations for the concentrate and convenient and useful package size for the bottle.
The final numbers - and the mix dilution chosen to go from concentrate to working solution - were influenced by the measurement system used - ounces, pints, quarts and gallons (all US). There are 8 US pints in a US gallon - thus the factor of 8x8=64 (63:1).
A European centred manufacturer would have been much more likely to end up with metric friendly relationships - 500 ml to make 10 litres being the choice made by modern Ilford.

Did Kodak take the same approach for suggested dilutions of developers, fixers, hypo clearing agents, and the like? Are the optimum dilutions of Kodak chemicals so unimportant that packaging convenience trumps them?

MattKing · Jun 23, 2023

faberryman said:
Did Kodak take the same approach for suggested dilutions of developers, fixers, hypo clearing agents, and the like? Are the optimum dilutions of Kodak chemicals so unimportant that packaging convenience trumps them?

Products were designed for ease and speed of use in a commercial environment. The make up of the concentrate and the choice of dilution was based on the photographic effectiveness and consistency that resulted. However, for most things like stop bath, a range of dilutions would have sufficed, but a particular one within that range was chosen, and that choice was influenced by considerations such as practical package sizes and commonly encountered final volumes of working solutions. If an 8 gallon tank was a commonly encountered one, a single 16 ounce bottle of concentrate could just be dumped in and diluted until the tank was full - no measurement required. That ease of use was a real advantage in the commercial world.
In times of yore, there most likely would have been a variety of package sizes, tailored to a variety of common uses.
All the other chemicals were somewhat similar - it was an ecosystem where considerations of end user needs and the practicality of matters like shipping and storage space influence the size of the cans, bags, bottles or boxes sold. And that ecosystem was mostly oriented toward commercial users - not the generally low volume users mostly found on Photrio.

BHuij · Jun 23, 2023

@koraks Interestingly enough, my tap water is actually quite well buffered from pH changes. Between darkroom printing, alt process, and keeping aquariums, I'm fairly intimately familiar with what comes out of the tap around here I have a lot of carbonates in my water (about 10 dkH), so it isn't quite so easy to swing the pH.

koraks · Jun 24, 2023

BHuij said:
my tap water is actually quite well buffered from pH changes

Well... 10dkh is equivalent to around 180mg/l calcium carbonate. That's an insignificant buffer in the context of photographic processing solutions.

koraks · Jun 24, 2023

Eugen Mezei said:
How will these stains look?

Mostly yellow discoloration of white and light areas of the prints; tends to pop up particularly on the borders and often is worse along the edges of the paper where chemistry easily permeates the fiber base.

Eugen Mezei said:
How can they be removed?

By incinerating the print. That's why it's probably a good idea to try and prevent them.

lantau · Jun 24, 2023

faberryman said:
So why not choose 126:1 and then a half pint bottle would mix up exactly eight gallons of working solution?

The explanation is very simple. You can't have acetic acid, which is stronger than 100%. According to the SDS, Kodak Stop Bath concentrate is actic acid at a strength of about 80-85%.

Another observation: that also means that, according to those, who say how dangerous concentrated actetic acid is for the lay user, most people here shouldn't be using this product.

But I've noticed that D76 and Xtol have this notice on the packaging: For professional use. That is from memory. Maybe there is even an 'only' at the end. Of course these developers contain borate. So strictly speaking it is not legal in Germany, probably the entire EU to sell these to consumers. At least not by mail order.

Maybe stop bath has the same notice on the container?

RalphLambrecht · Jun 24, 2023

DowntownDan said:
Hi all,

I use TF-5 for both film and paper and usually use a running water stop, but for reasons too tedious to enumerate, I recently lost light-tight running water and am running my trays in a blackout tent.

Without rubbing water, what’s the appropriate procedure for stopping prints prior to fixing with TF-5?

Do I just add time to the water stop? Agitate more vigorously? Split in into two trays and just move from one to the other halfway through?

Would I need to change the tray water for every print? Every 2-3 prints? Would it help to switch to a more dilute or slower-working developer?

I assume that with RC it would be less critical than fB as it’s easier to rinse off the developer.

Any help is much appreciated.

Dan

why not use a regular 2% citric acid stop bath?

faberryman · Jun 24, 2023

lantau said:
The explanation is very simple. You can't have acetic acid, which is stronger than 100%. According to the SDS, Kodak Stop Bath concentrate is actic acid at a strength of about 80-85%.

The question was intended to be rhetorical in nature.

bluechromis · Jun 24, 2023

MattKing said:
FWIW, the late Photo Engineer (aka Ron Mowrey) posted here on more than one occasion that TF-5 was co-designed by him to be strongly buffered, in order to be fully usable with acid stop baths, which in turn he recommended people use.

While the PE recommended using an acid stop for film, Bill Troop, who devised or co-devised the TF series fixers, argues in favor of alkaline fixers and water baths. The main reason I am aware of that the PE favored stop baths is that he had experienced instances of dichroic fog when not using an acid stop. As I understand it, that fog results from very strong developer and weak fixer. Bill Troop says it is very unlikely to get dichroic fog with modern films. I did not see the PE say when in his long career he experienced dichroic fog or if it ever happened with modern films. In any case, allowing one's fixer to become weak can lead to many problems and best to avoid it.

DREW WILEY · Jun 24, 2023

When processing film, whether in trays or a drum, I insert a brief plain water rinse between the stop step and the fixing step. That should alleviate any lingering questions about pH carryover. But I don't bother with that extra step when developing papers. I have a specific reason for that, but don't want to bother explaining it right now.

I still have several gallons of glacial acetic acid on hand, probably enough to make all the dilute stop bath I need for the rest of my life. I never mix it anywhere near as strong as 2%. No need to.

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