How can I prevent fresh blix from popping the Patterson tank lid?

Certain Exposures · Nov 23, 2025

I experience this issue with fresh chemistry, regardless of the C-41 kit I've tried.

I immediately 'burp' the Patterson tank lid by squeezing out as much air as possible when I fill it with blix. However, the gases cause the lid to rise as the tank spins, and I use a processor that holds the tank on its side. The gas forces me to disrupt the developing process to burp several times, and it causes a bit of leaking.

How can I avoid this issue without switching to a new tank style or changing my C-41 kit? I know ECN-2 does not do this. I prefer the simplicity of the two-step C-41 process.

I have no desire to switch to a Jobo tank or process because that setup is too large and expensive.

Is there an 'easy' win here? I wish the Patterson tank had a lid with more room to expand. That would be an improvement.

koraks · Nov 23, 2025

Use a stop bath (e.g. 1% acetic acid) between developer and blix. The tank will still need to be burped and the lid may pop, but the only thing lost is your virtually free stop bath. Then the blix won't pop the lid anymore.

Certain Exposures said:
I know ECN-2 does not do this

Yeah it does.

Certain Exposures · Nov 23, 2025

koraks said:
Use a stop bath (e.g. 1% acetic acid) between developer and blix. The tank will still need to be burped and the lid may pop, but the only thing lost is your virtually free stop bath. Then the blix won't pop the lid anymore.

Yeah it does.

Do you use distilled water for your stop bath or tap water? Have you noticed uneven development or 'splotchiness' on your negatives when you use stop bath during C-41 home development?

At one point, I tried a quick tap water bath between the developer and blix steps. I stopped (no pun intended) because I noticed uneven development/splotchiness when I did that. I suspected that the tap water in my area might contain impurities. I use distilled water for my developer and blix steps. I could try using distilled water to mix the stop bath.

koraks said:
Yeah it does

I don't recall my QWD Lab ECN-2 kits causing a similar issue with the tank lid popping. Maybe I have a rosy memory.

koraks · Nov 23, 2025

Certain Exposures said:
Do you use distilled water for your stop bath or tap water?

Doesn't matter; tap is fine. You need to mix a little acid into it; see my post above.

Certain Exposures said:
Have you noticed uneven development or 'splotchiness' on your negatives when you use stop bath during C-41 home development?

No; in fact, part of a stop bath's point is to prevent these issues.

Certain Exposures said:
At one point, I tried a quick tap water bath between the developer and blix steps.

Plain water is not a stop bath; there needs to be an acid in it. I suggested 1% acetic acid above.

Certain Exposures said:
I don't recall my QWD Lab ECN-2 kits causing a similar issue with the tank lid popping.

Whether the lid pops depends mostly on how much liquid you put into the tank, whether you depress the central part of the lid (so it can pop out, although this is not a 100% protection against spillage) and how well the lid fits in the first place. Whether or not the lid pops off is a bit of a random thing for these reasons.
Either way, a typical ECN2 process as people generally run it at home, involving often a ferricyanide bleach, should most definitely include an acidic stop bath after the developer (which will cause generation of CO2 gas which is what makes the lid pop), followed by a sulfite clearing bath and then the ferricyanide bleach.

pentaxuser · Nov 23, 2025

If it is any help and it may not be, based on what you have stated to koraks after his advice. I too only ever experienced a problem with the lid popping with stop bath and then only because initially I was not burbing the lid. I can't recall ever experiencing a problem with blix once I had burped the tank lid when using stop

In my case it was Jobo tanks on a Jobo processor so like you the tank was on its side continuously rotating and that I am sure added to the problem of popping

Frankly it might be just as easy to use the stop by inverting where it will still be inclined to pop but maybe less so because the tank is upright and if it does there is no loss of stop. Then use the blix with the tank rotating once agaín.

Worth a try but it's your decision

pentaxuser

loccdor · Nov 23, 2025

I burp the plastic bottles when mixing the C-41 chemicals. Shake them up a alot before developing the first film. Usually with the Blix, I squeeze the plastic bottle while it's 2/3 full with cap off, put the cap on while it's still squeezed, shake it up until it expands to full volume, then do it again a few times.

Certain Exposures · Nov 29, 2025

Thanks everyone. I will try testing an acid stop bath again next time.

This time I had important (to me) frames to develop so I went with my usual approach to avoid any surprises.

loccdor said:
I burp the plastic bottles when mixing the C-41 chemicals. Shake them up a alot before developing the first film. Usually with the Blix, I squeeze the plastic bottle while it's 2/3 full with cap off, put the cap on while it's still squeezed, shake it up until it expands to full volume, then do it again a few times.

Thanks, I use amber growlers instead of plastic bottles. I do follow the guidance to pour the blix back and forth between two bottles. That hasn't helped much so far.

blee1996 · Nov 30, 2025

I also use Paterson tanks for color processing (C41, E6, ECN-2). I only use inversion for all developers (and prebath if ECN-2), and use the twiddle for everything else (stop bath, fixer, bleach). I get consistently good results, thus consider inversion not necessary for blix.

My agitation regime with twiddle for bleach and fix: five turns clockwise and 5 turns counter clockwise in about 5 seconds. 30 second for the first minute, and then 15 seconds for each subsequent minute.

loccdor · Nov 30, 2025

Certain Exposures said:
amber growlers instead of plastic bottles

I used to use those but the extra weight combined with the fragility (not only from impact, but from heat changes) made me go back to plastic. While glass is less porous, my chemicals still last a really long time.

Samu · Dec 4, 2025

koraks said:
Plain water is not a stop bath; there needs to be an acid in it. I suggested 1% acetic acid above.

No, it is not. But as long as I know, there is one exception to the rule. when using water wash as a stop bath is mandatory for good results. It is E-6. The original process had an acid stop bath, but mainly, due to economical reasons, this was changed to 2 min water wash after FD. The composition of the first developer was changed to match with this change. So, the process works now optimally with the gradual effect of the water wash.

Certain Exposures · Dec 7, 2025

@koraks and @pentaxuser I assume you heat the stop bath up to the same or similar temperature as the developer and the blix? I am about to run a roll through the chemistry so I could test this again today.

Also, do you use the same stop bath for both C-41 and B&W until it's exhausted? Or do you use separate bottles of stop bath for color and black and white to avoid cross contamination issues?

koraks · Dec 7, 2025

Certain Exposures said:
I assume you heat the stop bath up to the same or similar temperature as the developer and the blix?

Yes; in general that's also the best idea, although in all honesty, the temperature of the stop bath isn't very critical. But it's good to avoid sudden temperature changes, so I'd keep the stop bath at around the same temperature as the developer and the bleach.

Certain Exposures said:
Also, do you use the same stop bath for both C-41 and B&W until it's exhausted?

I use it one shot. It's a very dilute acetic acid solution. It's essentially free anyway; there's no point in reusing it.

Certain Exposures · Dec 7, 2025

Thank you.

Samu · Dec 7, 2025

Certain Exposures said:
@koraks and @pentaxuser I assume you heat the stop bath up to the same or similar temperature as the developer and the blix? I am about to run a roll through the chemistry so I could test this again today.

Also, do you use the same stop bath for both C-41 and B&W until it's exhausted? Or do you use separate bottles of stop bath for color and black and white to avoid cross contamination issues?

I can´t answer on behalf of other people, but personally, I use different batches of stop bath for black & white and for C-41. I haven´t tested it, but the presence of carryover from other processes does not help in any way. Acetic acid is cheap. so this is not a question.

koraks said:
I use it one stop. It's a very dilute acetic acid solution. It's essentially free anyway; there's no point in reusing it.

I have used 3% acetic acid, as I´m too lazy mixing it all the time. It really is not important, if it is new or used, as long as it is acidic. The only reason for using 3% is my laziness of mixing new solutions all the time.

Certain Exposures · Dec 7, 2025

Thanks, @Samu .

pentaxuser · Dec 8, 2025

Certain Exposures said:
@koraks and @pentaxuser I assume you heat the stop bath up to the same or similar temperature as the developer and the blix? I am about to run a roll through the chemistry so I could test this again today.

Also, do you use the same stop bath for both C-41 and B&W until it's exhausted? Or do you use separate bottles of stop bath for color and black and white to avoid cross contamination issues?

It has been a while since I developed C41 but I am sure that as my b&w stop is in a Nova slot processor permanently I would have made it up separately for the Jobo and then placed it in a bottle that fits the part of the Jobo that holds the stock. If I only did one C41 film I would have kept the stop in the bottle and stored it for either some RA4 prints or another C41 film I would not have discarded the stop after one session unless I had done a printing session of several prints

I saw no point in dumping it after single use, be that one film or say 3-4 prints but neither is there any point in overusing it eíther

As for temperature, the stop bottle was in the heated water so came close to the "right" temperature anyway but as koraks says temperature for stop is not critical

pentaxuser

Certain Exposures · Dec 8, 2025

Thanks a bunch.

I tested this Sunday. Thankfully, I do not see the same splotchiness I saw in the past.

I wonder if that was because I used water as stop bath instead of acid. The instructor at my darkroom class taught us to use water as a stop bath for B&W film. Maybe I should reconsider that one, too.

This was the fourth time I used this batch of C-41 chemistry so I can't judge the impact on the blix popping the lid just yet. Usually the first three rounds are the worst.

loccdor · Dec 8, 2025

I use 3 agitated water baths as a stop bath except in rare cases. It works for almost everything.

Certain Exposures · Dec 8, 2025

@loccdor does that method work for you when you do C-41?

Correction: I do see some of the splotchiness that I mentioned was the reason I stopped using stop bath in the C-41 process. I went through more scans while editing. It's just not as obvious as it is with a pure water bath.

I'll have to share an example at some point. No promises on the timeline at the moment.

mshchem · Dec 9, 2025

My first thought is this is just air pressure not gas forming. Keep everything at the same temperature. Paterson tanks are poorly suited for rotary processing. The reel spins freely in the tank,

Jobo fixes the reel to the tank so when you rotate the tank the reel doesn't stay still or languish, it goes along with the tank. When the tank reverses, the reel reverses and it forces the solution to flow through the reel (and the film)

I developed a lot of color C-41 and E-6 in Paterson tanks over the years. Let the tank sit in a water bath. It could be a pain especially with 6 bath E6, had to baby sit it

blee1996 · Dec 9, 2025

In my Kodak C41 5L kit, there is no stop bath. Immediately after color developer, you pour in bleach. I suppose bleach will stop any remaining traces of developer.

mshchem · Dec 9, 2025

Yes, shouldn't need stop bath with standard C41 chemistry. But this is a blix kit. Certainly nothing unorthodox about using stop bath after developer.

loccdor · Dec 9, 2025

Certain Exposures said:
@loccdor does that method work for you when you do C-41?

Yes. Pretty much the only time I use stop bath is developing something special like Adox CMS 20 II that specifically calls for it. If several quickly agitated washes can remove fixer, I see no reason why they can't remove developer too. The one case I would consider using it (other than specialty films) is if your development time is extremely short. But I'm able to do the 3.5 minutes of C-41 without it in a Paterson tank no problem. But something I'm sure to do is immediately agitate very hard with the stick right when the water goes in. I wouldn't want to pour it in and wait around, it's going to be the quick agitation that does the work.

Others mileage may vary, isolate your variables and see what works for you.

Certain Exposures · Dec 30, 2025

Thanks everyone.

@mshchem , the processor I use accounts for that with something called a 'penguin'. Here's a video from back when I tested the prototype.

Certain Exposures said:
@loccdor does that method work for you when you do C-41?

Correction: I do see some of the splotchiness that I mentioned was the reason I stopped using stop bath in the C-41 process. I went through more scans while editing. It's just not as obvious as it is with a pure water bath.

I'll have to share an example at some point. No promises on the timeline at the moment.

@koraks I reflected on this and I think the splotchiness might have been from lens flares.

I used stop bath during my C-41 development again today. However, it was for a chromogenic black and white film. I doubt there will be anything worth commenting on. I will try stop bath on a few more test color rolls, eventually.

How can I prevent fresh blix from popping the Patterson tank lid?

Certain Exposures

koraks

Moderator

Certain Exposures

koraks

Moderator

pentaxuser

loccdor

Certain Exposures

blee1996

loccdor

Samu

Certain Exposures

koraks

Moderator

Certain Exposures

Samu

Certain Exposures

pentaxuser

Certain Exposures

loccdor

Certain Exposures

mshchem

blee1996

mshchem

loccdor

Certain Exposures

How can I prevent fresh blix from popping the Patterson tank lid?

Moderator

Moderator

Moderator

Privacy & Transparency

Privacy & Transparency