DIY Gas Burst Agitation for 1 gallon vertical tanks

[John Layton]

Was about to ask this also...about plastic. Small diameter pvc could be utilized...straight sections glued up with the appropriate curved or right angle sections. Or you could lay out three or four tubes side by side...connected at several points between them to allow gas to pass freely around...and leave a few end caps unglued but sealed until the pressure can be adjusted for evenness before final gluing.

Does any of this make sense? I ask because I've been thinking about gaseous burst...as a DIY project - and pvc is something I'm used to working with and its cheap...and available.

[Sam L]

John,

Yes, I believe plastic would work but you might need to design your tanks around it. PVC is a lot thicker than metal tubing. I only had about 3/4" at the bottom of my tanks and 1/2" at the ends. The plenum has to sit up 1/4" off the floor of the tank and I didn't want it to touch the hangers. For me, that meant the plenum had to be 1/4" in thickness.

I'm not sure how much easier PVC is than flexible copper tubing but if you have the tools and are comfortable with it I think that will go a long way.

Check out this excellent thread, which shows both commercial metal and home-made plastic plenums:
https://www.largeformatphotography.i...gen-Processing

There is historical guidance from Kodak. I never got my hands on the actual bulletin but many threads relay what it said: < 1/32" holes pointing downward in the tank; holes every half inch offset from the center line; plenum held off the floor 1/2". I suggest you really need 1/64" holes for a 1-gallon tank. There are a lot of ways to satisfy these specifications.

The overall goal is to evenly lift the entire volume of developer 5/8" with a 1 second burst. The claim is that the rise and fall causes the agitation more than the random bubble action. I think they both matter: the randomness of the bubbles creates random chemical wash patterns that blend out over the development time.

A bad plenum will lift some part of the liquid more than the rest, creating a wave and uneven agitation. I saw this with my first attempt (the S-shaped stainless version). This happened because the holes were too big (1/32") and the plenum didn't form a loop.