Xtol & Pre-soak

mshchem

Subscriber
Joined
Nov 26, 2007
Messages
14,663
Location
Iowa City, Iowa USA
Format
Medium Format
I remember in high school the H&W Control Film guys coming around telling people that acid stop bath created small explosions in the emulsion.

I used a lot of Plus-X. D-76 and Microdol-X. When I discovered medium format (my meager funds allowed me to aquire a Yashica TLR) I learned how to use a light meter and sunny 16. It was a miracle.
 

PhilBurton

Subscriber
Joined
Oct 20, 2018
Messages
467
Location
Western USA
Format
35mm
I have to say that as someone who hasn't done film development for about 30+ years now, but plans to start doing B&W again "soon" (whatever that means with the corona virus) I found this thread very instructive. I never did a pre-soak before, and I always used acid stop bath. That's what I will continue to do. The only difference from before is the choice of developers. Going forward I will start with Xtol.
 

RalphLambrecht

Subscriber
Joined
Sep 19, 2003
Messages
14,654
Location
K,Germany
Format
Medium Format
this is almost the question of religion. You will find strong believers in each camp. I do not presoak because I never saw a benefit. However, some believe that has the benefit of getting drum spiral and film to the same temperature as the liquid. I suggest sticking to manufacturers recommendations.
 

Donald Qualls

Subscriber
Joined
Jan 19, 2005
Messages
12,301
Location
North Carolina
Format
Multi Format
mshchem said:
I remember in high school the H&W Control Film guys coming around telling people that acid stop bath created small explosions in the emulsion.
Click to expand...

This is more or less correct with carbonate developers and very thin or soft emulsions. The carbonate evolves carbon dioxide gas by reacting with the acid, and the gas inside the gelatin creates bubbles that read in the print) as dark spots with light halos -- holes in the image silver surrounded by regions of increased density where the silver is compressed by the bubble.

This happens only with carbonate developers. H&W Control is one such, hence the warning. The films that developer was aimed at have very thin emulsions, as well.
 

john_s

Subscriber
Joined
Nov 19, 2002
Messages
2,141
Location
Melbourne, A
Format
Medium Format

I'm not religious about prewashing, and not trying to convert anyone.

But why does the displacement of water by developer NOT occur evenly, as long as one agitates as normal?
 

Donald Qualls

Subscriber
Joined
Jan 19, 2005
Messages
12,301
Location
North Carolina
Format
Multi Format
And moreso (despite that reasoning by analogy is always suspect) -- have you noticed that a fully dried sponge takes much longer to absorb anything than one that's been dampened first? In the case of gelatin, the swelling that occurs when it's immersed in water (whether that water is reasonably pure, or "contaminated" with alkali, halide solvent, and one or more phenol-based reducing agent) opens up the spaces in the "sponge" -- letting water in and out more easily than dry gelatin would.

The confirmation that it does no harm would be processing with a two-bath developer after a pre-soak. If wet gelatin takes longer to absorb developer, you might get lower contrast "underdeveloped" negatives (assuming the recommended Bath A time is only just what's needed for the developer to soak in, rather than prudently longer), compared to pouring Bath A onto dry film. In order to really tell you'd probably have to run tests to see what minimum Bath A time is required for normal results with dry film and with wet.
 

MattKing

Moderator
Moderator
Joined
Apr 24, 2005
Messages
52,980
Location
Delta, BC Canada
Format
Medium Format
I expect that it is essentially the opposite of what NB-23 suggests.
One way of assuring even take-up of developer is to pre-soak. You sometimes need to adjust the development time to take into account the effect of the pre-soak.
The other way is the way that the film manufacturers went - adjust the chemistry to ensure even take-up of developer when a pre-soak is impractical or reduces efficiency. The latter approach being clearly advantageous to higher volume commercial development lines where minimum time and high throughput are highly valued.
 

Andrew O'Neill

Moderator
Moderator
Joined
Jan 16, 2004
Messages
11,989
Location
Coquitlam,BC Canada
Format
Multi Format
The only film I ever prewashed was tmy-2 sheet film. I use BTZS tubes. If I didn't prewash in a tray first, a blue band of antihalation would be left on the film, that took quite a while to remove. Sadly I don't use that film in LF anymore as it's just too costly.
 

RalphLambrecht

Subscriber
Joined
Sep 19, 2003
Messages
14,654
Location
K,Germany
Format
Medium Format
This works for me too; two minutes in hypo clearing, clearing followed by a 10-minute wash and the bank is gone!
 

NB23

Member
Joined
Jul 26, 2009
Messages
4,307
Format
35mm

i will contradict you. And yes, the analogy is correct.

First of all, you seem to totally forget (probably on purpose) that modern films are engineered to wet evenly when dry. I’m not sure why you must contradict.

But let’s get back to the sponge. Have you ever had a sponge filled with paint? Like when you clean a mess of paint with a sponge? You would notice that the diluted paint inside of the sponge is very, very hard to totally evacuate. Even after many squeezes. This takes time, and it obviously is not happening in a linear/even fashion.

But now, surprise (!) you can’t squeeze film. So you must let the action of the water alone displace what’s inside of it and replace it with clean water.

I invite you to make the following experiment yourself. Take a sponge filled with paint and NEVER SQUEEZE IT. Leave it under running water for 10 minutes, in your sink. Then, after 10 minutes, stop the running water and wait One minute for the water to drip out of the sponge, without touching it. After one minute has passed, take the sponge in your hand and squeeze it. You will see, your squeezing action will syphon out paint colored water. This will show you how difficult it is to clean a sponge without squeezing action.

At last, please realize that my example is not an analogy. Film and paper emulsion are indeed Sponges.
 
Last edited:

Bormental

Member
Joined
Mar 1, 2020
Messages
622
Location
USA
Format
Multi Format
Sponges my a$$. Why not use paper towels as an analogy? It sucks water in like nobody's business. Instead of pontificating on matters you know nothing about, just read the freaking manual, it says whether to pre-soak or not (depends on the emulsion, of course).
 

NB23

Member
Joined
Jul 26, 2009
Messages
4,307
Format
35mm

Do you presoak toilet paper before whiping? I hope not, imagine the unevenness...
 

Donald Qualls

Subscriber
Joined
Jan 19, 2005
Messages
12,301
Location
North Carolina
Format
Multi Format

NB23 said:
i will contradict you. And yes, the analogy is correct.
Click to expand...

No analogy is ever "correct" -- there are many that are incorrect at a level that makes them useful (electricity as water in a pipe system, for instance), but analogy always breaks down at some point.

The point at which the "emulsion as sponge" analogy breaks down is where you start to think of it as actually being a sponge. Water doesn't need to flow in and out of the gelatin, it just needs to be filled and swelled; once that's the case, chemicals dissolved in the water can diffuse in and out as well. They'll diffuse more slowly than they would in unhindered water, of course, but the water doesn't have to flow for this to occur. I reposted above the actual, simple, scientific test to determine if there's any advantage of disadvantage for presoaking with a particular film (independent of convenience issues like antihalation dyes). Rather than standing in the middle of the room screaming about how right you are, how about testing it? Then, whichever way your testing comes out, the next time this comes up (and it will, as long as we have film, developer, and water), instead of reasoning by analogy and giving thought experiments, you can say "back in 2020, I tested this using two-part developer X, and for film Y, the minimum required Bath A soak after a pre-soak is Z time (longer or shorter) than on dry film."

If you don't, I will, but it may take some time to load, shoot, and process enough film to arrive at the minimum Bath A time -- and that answer will only apply to one film (or, at best, one film family).
 

MattKing

Moderator
Moderator
Joined
Apr 24, 2005
Messages
52,980
Location
Delta, BC Canada
Format
Medium Format
Of course, in most cases, the "manual" is either silent about pre-soaking, or only refers to it in the context of continuous rotary processing.
This is how conspiracy theories are born!
 

Michael Teresko

Subscriber
Joined
Dec 22, 2018
Messages
70
Location
Oakland, CA
Format
Multi Format

The one time I tried a two bath developer, I used divided pyrocat-hd. I presoaked, as is recommended for PC-HD, and wound up with very uneven and underdeveloped negatives. I've read that presoaking may have been the cause, as the developing agents don't properly soak into the emulsion. Which raises the question, if presoaking is detrimental to even development, why is it always seem to be recommended for pyro developers?
 

Donald Qualls

Subscriber
Joined
Jan 19, 2005
Messages
12,301
Location
North Carolina
Format
Multi Format
What was your Bath A time? Is Pyrocat-HD recommended for divided use? Did the recommendation for a pre-soak in PC-HD specifically apply to the divided version?

Uneven/underdeveloped negatives in a two-bath developer are usually a result of insufficient Bath A time, leading to limited carry-over of the developing agent(s) into Bath B. This can also cause unevenness, as the insufficient developer will exhaust in highlights -- possibly quickly enough to badly undermine contrast, resulting in a very early shoulder and "flat" looking highlights.

Pre-soaking might also be beneficial for Pyrocat-HD and detrimental for Divided PC-HD (or simply dictate an extended Bath A time), because the relatively large pyrocatechin molecules may not diffuse into the wet gelatin rapidly enough in the divided Bath A, vs. being carried into dry gelatin with the water as the gelatin swells. That's part of what I'm recommending be tested to settle the question of when it is and isn't a good idea to pre-soak.
 

john_s

Subscriber
Joined
Nov 19, 2002
Messages
2,141
Location
Melbourne, A
Format
Medium Format
Maybe for divided development, if you want to presoak, a longer time in Bath_A would be in order. Extra time in Bath_A would not be a problem, would it?

(Here I'm assuming a true two part system, not a normal developer followed by an alkaline bath)
 

Donald Qualls

Subscriber
Joined
Jan 19, 2005
Messages
12,301
Location
North Carolina
Format
Multi Format

Correct, for a true two-bath developer, no development (or almost none) takes place in Bath A -- adding time to allow the developer to soak into emulsion will do no harm.

Something occurred to me, @NB23 . If starting with wet film causes unevenness, how do we account for the fact that every reversal process does this (perhaps we only get away with it because the second developer is carried to completion?), and C-41 processes routinely recommend it (for a 3:15 to 3:30 process!)? And in two-bath processes, Bath B is always introduced to wet film -- yet we don't seem to routinely get uneven development here (perhaps because in this case development is carried to complete exhaustion?).
 
You must log in or register to reply here.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…