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> Protective gas for chemicals in bottles |
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#21
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I use PoundLand Air Duster spray - comes with a tube (like some lubricants do) is typical propane/butane mix.
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#22
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https://www.poundshop.com/air-duster-aerosol-200ml.html https://www.poundshop.com/gas-lighter-refill-300ml.html Terry S |
#23
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Might be worth seeing if the Poundland air duster cap with the "straw" fits the Poundland lighter refill can - best of both worlds!
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#24
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Preservation
Going completely off pist here.
Using any inflammable gas in an enclosed space such as the darkroom is just too damn dangerous for me. All it needs is a small spark created when switching something on is enough. Preservation of chemicals, especially the developer is quite important, but different developers have different rates of decomposition once they are mixed. Excluding any oxygen with an inert gas blanket may sound like a good idea but may very well be a waste of time. I tried Tetenal a long time ago and found it to be only slightly better than a waste of money. Some developer concentrates will go off, irrespective what you do unless you can use them up in a short time. (Ilfosol is one that come to mind) For may years I have adopted the principal of decanting developer from the main container (E.G. Multigrade developer in 5 litre cannisters) into 10 1/2 litre glass bottles - they must be glass with plastic inserts in the caps. I don't use a very large quantity of B&W developer these days because I largely print colour. Once the developer is decanted out and stored in the sealed glass bottles, it is then further decanted out into 5 x 100cc bottles when I need to which is enough for an evenings printing. I have used MG developer up to at least 1 year after it was transferred into the smaller bottles and it was just as good as fresh. I don't obviously know what film developer you use, but my staple is ID11 or D76, whichever is the cheapest when I am buying. Once mixed and again stored in the glass bottles the life is AT least 18 months. I know others like FX39 and Rodinal have a long life anyway. A long time ago I used a home made developer called Beutler and that had a shelf life of seemingly indefinite years. It was a poor man's Rodinal! Google the name and you can get the formula. It is even still listed in the Digital Truth charts. Colour film developer is also very stable stored this way, in fact the C41 developer of choice for me is Digibase in 5 litre kits. That has a life after opening (but not mixed) in excess of 8-10 months. I know this because I am 3/4 of the way through a kit and there is no discolouration of the main parts of the developer, so long as they are not pre mixed. Even if pre mixed but not used they can last a couple of months RA4 developer. (Apart from my recent misguided change from the Kodak Ektacolour RA4 to ADOX) I have always found the Kodak RA4 to be very stable and long lived, even when mixed and partially used in a NOVA tank. It must be regularly replenished and I do this after every session. I keep a check list of how much I have printed and replenish as needed. Like MG developer when I mix the replenishment RA4 I generally make 1 litre and split them into the 100cc bottles, each of them is sufficient fresh developer for 800 sq ins of paper. That is 10 sheets of 10x8) In the past I have used RA4 in a NOVA for close on 12 months because of regular replenishment and only then cleaned it out to reduce the build up of tar. It may sound a bit drastic but when I mix the RA4 replenisher, I heat the full but still uncapped bottles in a small microwave (not the household one) to around 50C and then screw the caps on. As the liquid cools the volume physically decreases and it forms a semi-vacuum inside the bottles which means less oxygen, and in theory a longer life. But going back to basics. all water will absorb oxygen, that is a scientific fact. Fish could not live in water unless it did. All my mixing water for long term RA4 is boiled first which drives off the dissolved oxygen and water with very little oxygen present in the 1st place. I would suggest this is far better than covering the surface of chemicals with an inflammable inert gas or any inert gas. You are only trapping dissolved oxygen in the chemicals to carry on degrading the contents anyway. It is not the oxygen above the surface it is what is dissolved in it in the 1st place. The bottom line is, you can do almost anything to preserve chemical activity but given time they will all loose effectiveness. Last edited by John King; 16th February 2022 at 08:58 AM. |
#25
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I read the instructions on a tin of Tetenal Protectan today.
It reads "DO NOT turn the can upside down during spraying." When I tried inverting and spraying it blasted out a stream of liquid gas. Cheers.
__________________
It will all be over by Christmas. |
#26
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I am most of the way through my current can of Protectan and have two in reserve. I'm glad to think that I can just use them and be spared all the complicated speculation generated by this thread. They last 6 or 7 years each and I'll be 79 shortly.
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#27
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The 'speculation' suggested about protecting developer by spraying a small amount of inert gas to cover the surface in the long run cannot work for the reason I mentioned, i.e. the dissolved oxygen will continue to decay the developer anyway, at best it will only slow it down.
Think of it this way by means of an analogy. If you are trying to preserve a piece of furniture by painting it, but then you find it has woodworm. you have to destroy the woodworm before applying paint because the little blighters will continue to enjoy a 1st class meal. |
#28
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My chief issue is Ilford Multigrade developer concentrate, after the bottle has been opened. Ilford's technical data sheet says "Once opened use the concentrate completely within six months". I don't know whether my darkroom has exceptional oxygen levels, but the concentrate always turns dark brown before I reach the end of the bottle, always well within six months. This cannot be the result of oxygen already in the water, otherwise it would have oxidised before opening. Ilford used to advise against using developer that had oxidised beyond a pale straw colour, but I was never clear whether this referred to the concentrate or working strength. I liked to imagine it meant the latter, because that gave me more leeway. Maybe the advice was given only for 'stock' developers like ID-11? I have actually never noticed any bad effect from using visibly oxidised print developer concentrate: no precipitates, no staining, no obvious loss of potency. I wonder what proportion of the developing agent has been oxidised when the concentrate has reached, say, the colour of beer (taking Old Hooky as a standard, perhaps)? |
#29
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If there is one thing this thread confirms its that nothing in photography is cast in stone and can be seen as a precise science. Black and white photography is not black and white. It applies to practically all aspects, type of developer, vigerious or gentle agitation, stop bath or water or acid or alkali, tempertatures, process times, shelf life, film box speed or not, exposure calculation, etc. etc. The only thing that matters is what works for you, Wise people listen to all views, take note and then form their own opinion on their own practical experience.
I will now run for cover, bye. Tony Last edited by Tony Marlow; 17th February 2022 at 10:13 AM. |
#30
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That was split from the 5 litre container around 14 months ago when I rebuilt my darkroom. That 6 month instruction to use it completely will be due in part to an open bottle is at more risk of oxidisation and if they didn't make it known that this may happen could leave themselves open to litigation. What is common sense to one person is a key to making a quick buck to another. I have yet to have my staple film developer ID11 or D76 'go off', because they too are stored in glass not plastic bottles. After over 55 years using a darkroom I know what works and what doesn't Possibly why fresh chemicals don't 'go off' may be due to the likes of Ilford and Kodak using a preservative or even de-oxygenated water in the make up we simply do not know. I do believe though that using a gas to preserve chemicals in a bottle is akin to snake oil. Last edited by John King; 17th February 2022 at 11:11 AM. |
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