How strong to tap the bottom to free the air bubbles?

[arigram]

This is the right approach with me.

You mean with your film tank or your own naughty self?

 

[naugastyle]

About half the impact of rock-paper-sizzers.

Couldn't be clearer.

I find I tap too hard, but it's due to frustration from having 3 rolls come out with bubbles. Considering that until the first roll happened (1 1/2 years ago) this had NEVER happened before and I'd never made any sort of special tapping effort, I was baffled. Especially when it happened twice more. I do worry about cracking the tank though so I should probably pull back a bit.

 

[Tom Stanworth]

This is a bloody good question. It is all down to where you are. I have never had problems in the UK but have severe problems in Kabul. see this thread for solutions to drying marks (another problem in Kabul) as it also helps on air bubbles too. FWIW, although I can dislodge some air bubbles by banging th base of the dev tank on a hard floor, I cannot remove them all. Adding a tiny amount of wetting agent to the dev seems to help a lot.

(there was a url link here which no longer exists)

 

[Willie Jan]

If you drop it on the floor, the bottom will get cracks and light enters the tank...

Be gentle with it!
I never tap it, if you gentle rotate it f.i. the first minute and have a presoak before the developer is put in, this will not be a problem at all.

 

[Martin Aislabie]

How do we know without opening the tank to look? Maybe an experiment with outdated or sacrificial film would be in order. I use such vigorous agitation that there sholud either be no bubbles or bubbles everywhere, But I still give it a good rap when I set the tank down.

This is very good advice

Sacrifice a film - it pays dividends in the long run.

I not only "drop" my tank (somewhere between half and once inch) but I also give it a generous (vigorous) rotating wiggle too

It is most critical at the initial fill, when the air can stick to dry film and/or reel.

At subsequent agitations the tapping and wiggling can be reduced

Its amazing down tenacious air bubbles can be.

It’s something of a Catch22 situation – you need enough spare room in your development tank to allow thorough turbulation (hence mixing) of the developer, without excessively aerating the developer

Some films/developers/water types are more likely to aerate than others – so its worth checking how your combination behaves.

Martin

 

[CBG]

The bottom of your stainless steel tank should look mangled like you assaulted it with a large hammer.

Ummmm ... wait, wrong forum.

No, go gentle.

 

[Sirius Glass]

Firm but gentle.

 

[NormanV]

You've got me worried. I have not had a problem with air bubbles in 40 years, now you have all made me think that I am doing it wrong.
I give a couple of gentle taps with the tank on the ss draining board, 3 or 4 inversions (depending on how energetic I feel) then 1 inversion per minute.
I have noticed the water from the drinking fountain at work is milky until the air bubbles clear but fortunately I don't have that problem at home.

 

[Steve Smith]

This reminds me of some advice my father gave me many years ago on how tight to do up motorcycle cylinder head bolts. He said "do them up until they break then back them off a quarter of a turn!".


Steve.

 

[bobwysiwyg]

This reminds me of some advice my father gave me many years ago on how tight to do up motorcycle cylinder head bolts. He said "do them up until they break then back them off a quarter of a turn!".


Steve.

Yeah, who needs those pesky torque tables.

 

[Sirius Glass]

Yeah, who needs those pesky torque tables.

Years ago, I saw a neighbor putting the heads back on his car. He was sitting in the engine compartment with the ratchet wrench saying, "Torque, torque, torque ..." as he tightened the bolts.

Steve

 

[Tom Stanworth]

if you live in an area where water, temp, humidity of whatever the hell it is conspires to put bubbles on your film, rapping the tank WILL NOT solve your problem. Trust me, I have been there for three years. Tapping tanks removes large air bells and some bubbles, but most bubbles remain.

I even have one spiral that for reasons unknown will put lots of small clusters on one or two frames of every film you use with it...

 

[Rolleiflexible]

if you live in an area where water, temp, humidity
or whatever the hell it is conspires to put bubbles
on your film, rapping the tank WILL NOT solve your
problem. Trust me, I have been there for three years.

I believe this to be true. Not
infrequently I get bubble marks
in my negatives, even though I
slam my tanks (steel tanks, Hewes
reels) hard against the steel sink
rim. For example:

http://www.flickr.com/photos/sandersnyc/2591542119/


It's a nice but ineffective idea,
at least for me. Like much of
photography, I believe this
practice to be an old wives' tale,
without any demonstrable basis.
(Yet I still do it, for fear that
the bubbles would be even
worse without it.)

 

[Ian Grant]

Here's what you get

No amount of tapping removed them completely, this was after sharp taps !!!

Commercial developers often contain a water softening/sequestering agent & sometimes a trace of wetting agent. But sometimes this isn't enough in certain areas.

Tom & I have talked about this in another thread recently, both of us have particularly poor tap water.

I've eliminated the problem entirely by adding a couple of drops of wetting agent per litre of working strength developer. Care is needed because too much wetting agent will cause foaming and give worse problems.

Ian

 

[Perry Way]

if you live in an area where water, temp, humidity of whatever the hell it is conspires to put bubbles on your film, rapping the tank WILL NOT solve your problem. Trust me, I have been there for three years. Tapping tanks removes large air bells and some bubbles, but most bubbles remain.

I even have one spiral that for reasons unknown will put lots of small clusters on one or two frames of every film you use with it...

In this case, what would be wrong then about a pre-wash with straight distilled water to ensure uniform wetting (as well as extending life of fixer), followed by using one-shot developer that has been mixed with distilled water also? It seems logical to me this is a case when you spring the extra $0.75 a gallon it costs to buy distilled water.

 

[Ian Grant]

You can get these air bubbles happen with distilled water too, so a pre-soak isn't necessarily the answer. Agfa recommended not using a pre-soak for this reason 100 years ago

Ian

 

[B&Wpositive]

I literally *slam* my tank down on the floor pretty hard several times. Somebody's probably going to tell me that it's not a good thing to do, but I do it because I used to get clear spots on my film.

I'm not a pre-soak proponent.

 

[clayne]

This slamming and pounding that some people are doing all seems like overkill. I rap it against a towel covered surface a few initial times after filling it to the brim (stainless tank of course). Never had a single problem with air bubbles.

 

[Rolleiflexible]

This slamming and pounding that some people are doing all seems like overkill. I rap it against a towel covered surface a few initial times after filling it to the brim (stainless tank of course). Never had a single problem with air bubbles.

It was a gradual escalation, from
loving taps to sharper raps to
hammering nails. Throughout,
the bubbles persist.

 

[Martin Aislabie]

This slamming and pounding that some people are doing all seems like overkill. I rap it against a towel covered surface a few initial times after filling it to the brim (stainless tank of course). Never had a single problem with air bubbles.

Quiet how much GBH you need to apply to your tank to displace the air bubbles varies enormously and is dependant upon a number of factors

Clearly it varies with both Developer and water quality.

If you only need to tap gently – then you are lucky

I have to tap and wiggle/shake my tank quite hard.

Ian G needs to resort to adding tiny amounts of wetting agent.

We are all trying to achieve the same thing (no air bubbles) – but what we have to do to get there varies considerably (YMMV!)

Martin

 

[Xmas]

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.

Noel

 

[Ian Grant]

Visual tests

Ian G needs to resort to adding tiny amounts of wetting agent.

We are all trying to achieve the same thing (no air bubbles) – but what we have to do to get there varies considerably (YMMV!)

Martin

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.

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.

Ian

 

[Martin Aislabie]

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.

Ian

I too have done this, firstly with plain water plus empty reels and repeated with Dev and sacrificial Film

Its alarming just how persistent and tenacious the air bubbles can be

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

Martin

 

[removed account4]

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!

 

[Ian Grant]

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.

Ian