Air bells can be eliminated by thumping the tank on a hard rubber pad several times each new chemical is poured in AND filling the tank to completely cover the top film.
I'm did that, and some of the air bells was on the bottom reel. No atter how hard, within reason, or banged, rapped etc. the air bubbles would cling to the top of the reels. The only way I could get rid of the bubbles was to use the stirring/twizzle stick, but this gives uneven development of the edges and center of the film.
That's fine as long as you have used stainless steel tanks and do not have airbell problems with them. I must admit to being unsure as to whether this was the case. All I could work out from what you said was that you were switching but not that you never had airbell issues with film on a stainless steel reel in a stainless steel tank
pentaxuser
No air bells with the stainless steel reels I borrowed from a friend.
This is an image from one of the films developed with the Paterson reels, showing the air bells. This is the worst example I got, most of the films had a lot less marks.
One of the rolls developed in stainless steel, the whole roll was just the clouds, and no airbells. Other test films (white wall indoor so even exposure of the whole frame) also show no marks.
And never use sparkling water.
Hehe ;o)
I used to get the occasional air-bell years ago but none at all when I started pre-washing the film before pouring the developer (quickly!) into my Paterson System 4 developing tanks. Actually I use four changes of water before the developer in order to wash out the dyes in the film. Ilford suggests prewashing is not necessary but since I use replenished Xtol the dyes have to go out otherwise they would accumulate in the replenished Xtol stock. The lack of air-bells is a side benefit. And I use at least 10% more developer volume than Paterson suggests to fend off surge marks.
I tried with and without pre-wash, with and without wetting agent, still got air bells no matter what with Paterson reels.
I agree also. Some water taps/faucets have what appear to be mini multi jets which can cause the water to foam and so trap air in the liquid.
I must admit I never had airbells in all the years I developed B&W. I never banged the tank but I did gently stir the water in the mixing cylinder and leave it for about 15-20 minutes before finishing the developer and water mix.
The D-76 stock is always resting 4-5 days after mix from powder. The working solution is being tempered, takes anything from 15 min to an hour, depending on ait temp. I'm mixing stock and water gently with a stirrer, and waiting to ensure all air bubbles ahve left the developer.
The reason for not trying to "fix" this issue is that I five years ago had the same experience with other brand new Paterson reels, so it must be something in my environment which causes the issues. Instead of spending too much time, film and chemicals trying to fix it, it is more efficient to use stanless steel instead. I just wan't reliable results, and I'm not religious about how I get them, as long it follows the path of least resistance. I prefer to make images, not to tinker with chemicals ;o)
When I tested tap water, it was filtered through a Paterson water filter, and left to settle down. But normally I use demineralised water for the developer.
Once again, thank you all for your kind help.
/michael