This post has been modified after its initial publication because further testing revealed problems with the described method of drying film. Under some conditions it may still result in acceptable results.
The part of my film development process that is still iffy is drying. Dust specks embedded in the emulsion; chemical streaks when using a wetting agent; mineral water marks if not (even with a final distilled water bath). What has worked best so far is to physically remove the water from the film before hanging it to dry. However that is prone to scratching the film. Especially when using a reusable film squeegee. I want a mostly fool proof process to not worry about screw ups with “important” photos.
If one is interested in this problem and search for solutions, for example on https://www.photrio.com/forum/home, it becomes evident that many people have problems with drying film with a good results. The solutions are as many as there are people having problems. I have tried many of them with varying results.
I got this idea that perhaps a ventilation fan would be able to blow most water off the film before hanging it to dry in the shower cabin. Possibly also subconsciously inspired by https://philipus.com/project-film-dryer-prototype). Blowing air on film requires that it be filtered or there would be lots of dust permanently stuck in the emulsion.
The resulting monstrosity (around 85x50x30 cm in size) is built using readily available ventilation supplies and blow filtered air on film reels.
The fan I procured is not strong enough to blow water off of film so the initial idea for this device failed. The film dries by evaporation in around 20 minutes using slightly heated air or 30 minutes using room temperature air. Drying using heated air in this way results in a stronger film curl (since it dries on reel) and may also dry the film unevenly. In the picture the film is held at a specific angle against the light to make the effect more pronounced. The uneven drying is just barely visible when drying using room temperature air. I don’t think it would show up in prints or scans. Both the amount of film curl and uneven drying patterns seem to vary with film type. I have tried 3 different film types.
Another disappointment is that the problem with water marks persisted. It’s quite easy to remove water marks on the shiny side of film though. For example by using a clean microfiber cloth, possibly dipped in some distilled water or isopropyl alcohol.
The key takeaway from this project is that the air filtration really works. There was no dust in the emulsion in any of the 10 or so test films I dried using this drier.
Maybe the next step is to build a full height dryer as I have the necessary parts now. It’s basically just an air tight cabinet that is around 180 cm high. It could be made quite narrow but would definitely have to live in our basement if it is ever built.
Tested modifications not shown in the video.
After having run quite a few undeveloped rolls of films through the device to observe effects I finally worked up the courage to do a live test.
This is probably my cleanest developed film yet. There are actually no water marks even though I frequently observed such during the simulated test runs. There are also no signs of uneven emulsion side drying.
There is some moderate film curl caused by the on reel drying but nothing troubling. Here’s the film hanging to really make sure it’s dry before sleeving.
I will not bore you with the full details of my development procedure. Here are the bits that I think matter.
A final bath in distilled water with a weak wetting agent solution for 10 minutes. The wetting agent was Tetenal Mirasol 2000 diluted 1:1000 instead of the prescribed 1:400. This is accomplished by preparing a stock solution diluted 1:10 in isopropyl alcohol and then diluting this 1:100 in the distilled water.
Shake of as much excess water as possible before placing reel in the drying tube.
Dry using room temperature air; in this case 22 Celcius and 50% relative air humidity.
Dry for 35 minutes using moderate air speed. I don’t have the means to quantify this, the RPM controller was used to lower fan speed.