When I remember I hold the top and bottom of the tank in each hand and take the bottom hand in a circular path, simplest to try it one handed with coffee in a cup over a sink, to stir in the sugar.
But then I never get air bubbles, lots of dust, insects etc. yes, no bubbles... soft water wets better.
Unlike the rest of you I've done some practical experiments with a tank, reels etc, taking the lid off to see what happened, in fact a few times - first with plain water and no film and once I thought I'd solved the problem then again with some old film & dev.
Originally Posted by Martin Aislabie
Having had a Paterson tank with 7 rolls of film split when giving it a tap I don't advocate sharp taps
Here's a few things I found last year:
1. No amount of tapping removed air bubbles totally, although in some cases it ma be enough for then not show.
2. Nor did inversion agitation.
3. If you have the Paterson twist stick to agitate by turning the spirals that helps.
4. Two drops of Wetting agent entirely solved the problem, with the surface tension broken air bubbles disappeared completely and didn't reform.
Then some comments.
5. Developers and films vary some developer/film combinations may be more prone to air bubbles than others.
6. Water supplies are very variable, this will make a significant difference..
7. The main conclusions are that some developers may contain too little sequestering agents for certain water supplies, and in most cases when you mix up yourself from scratch won't necessarily contain any sequestering agent.
In my case using Pyrocat HD there's no sequestering agent but wetting agent has proved sufficient even with the very high salt/calcium levels of my local water supply. In the 16 months since changing my way of working I've had no air bubble marks on negative.
My suggestion to anyone having persistent problems is do some visual tests with your tank and some dry spirals, you'll find it can be hard enough to dislodge the air bubbles with no film loaded, it's even worse with a film in the spiral.
If you do this you should find what will works best for you.
I too have done this, firstly with plain water plus empty reels and repeated with Dev and sacrificial Film
Originally Posted by Ian Grant
Its alarming just how persistent and tenacious the air bubbles can be :o
As Ian says, everyone should try it
My standard Dev is ID11, which has enough wetting properties to assist in the task of dislodging the bubbles.
I have always steered clear of Pyro Devs because they seem to lack the wetting ability of the main stream devs like ID11/D76
However, I am still curious how the air bells seem to seek out and randomly attach themselves to some of my best negs
i never knew there was a special and significant
technique to rap the container to get the bubbles off ..
other than just hitting the tank on the side or bottom of the sink ...
this thread has been quite a read, thanks!
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It's also worth mentioning that often water supplies can vary in some areas.
In the UK my local water comes from two sources, either the very soft Birmingham Welsh water from the Elan Valley reservoirs or local boreholes which is very hard, it can also be a mix of the two.
Here in Turkey it's again from reservoirs but quite hard water, but when they dry up or run low in the summer we switch to a borehole and that water has a far higher salt/calcium level as we are very close to the sea. Either way none of it is drinkable
So when people get intermittent problems it may be their water supply was switched for a short time.