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#11
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Getting B&W chemicals to that temperature will probably kill them - they are designed to work around 20C and getting them too warm kills them. Colour - designed to work at 38C - you are probably still within the "safe" window. However, is you do stopper the bottle at 50C and allow it to cool to 20C - you only reduce the air volume/mass by 9% - is it really worth it ? Martin |
#12
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Everything is also cooled to less than 20c, as my darkroom never gets up to those heady heights, even in the summer, normally it is around 15c. I always have to use back ground heating. Nor can I see how heating them up will 'kill' B&W chemicals, they are not organic. Can you say what you base this estimation on? I don't do the same treatment with B&W chemicals as they naturally last far longer. eg. ID11 or D76 when mixed will last for at least 1 year in glass screw top bottles. Rodinal will last far longer. Last edited by John King; 23rd January 2020 at 08:35 AM. |
#13
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#14
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Vacuum Pump Chemical Preservation
I can confirm vacu-vin or similar wine pump stoppers work very well, they hold the seal and chemicals last much longer than any other system. I have also had success with wine bags in a cardboard box with a tap however it was a mess and while much cheaper at first they won't last forever and require much fuss when filling.
It is true they don't remove 100% of the air however breaking up a 5L kit into 5 1L glass bottles means whatever amount of air leftover will only affect the current bottle your processing with (if one shot) as long as you get through that liter within a week or so I cant imagine there would be any difference than if you somehow managed to remove ALL of the air from a 5L bottle as you used it. Sent from my iPhone using Tapatalk Last edited by maxwellmakosk; 23rd January 2020 at 02:33 PM. |
#15
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When mixing B&W chems from powder you generally use 40C water to dissolve the chemicals so I do not think heating to 50C will cause any issues.
Heating the chems will reduce the amount of dissolved air/oxygen in the liquid but will not remove it completely - if it did, tropical fish would all suffocate . I'm sure a google search would find out the actual percentages at various temperatures. This is why you need to reduce the number (or, the total length) of tropical fish over cold-water fish in aquariums of the same volume. Nor am I convinced about the amount of air removed by small hand-pumps being worthwhile. There is a reason real vacuum pumps cost hundreds of pounds - generating a reasonable vacuum is difficult. I'm pretty sure the main advantage is due to decanting into smaller bottles with their attendant smaller air gap above. That, plus the use of the well-fitting, air-tight seal, will help considerably as many bottle seals are pretty poor, often made of permeable plastic or waxed card etc. Taking out perhaps 20% of the air (I would be amazed if it is more) does not hurt, but I doubt that it is the main contributor - the excellent seal it provides is my best guess at where the major advantage lies. Regardless of all that, it certainly works but I would not rely on the "vacuum" alone. Once you have more than a few ccs of air, I think it's time to break out the Protectan/Argon/butane camping gas/butane lighter fuel/etc... |
#16
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Vacuum Pump Chemical Preservation
According to MLI Physics collection page 22 a vacu vin or similar can pull 400 mbar before the *click* which is quite substantial, almost half an atmosphere. Ill bet you could easily remove 50% of the air pulling past the click. Apparently people have broken wine bottles with them so I guess they can achieve the max pressure the glass can handle anyway. If going down the vacuum route it seems like a pretty good deal. Of course marbles, co2 is better if we're taking about amount of air removed.
I agree with Bob though I don't think even half an atmosphere is enough air to make a massive difference. But I imagine I helps create a good seal. Sent from my iPhone using Tapatalk Last edited by maxwellmakosk; 23rd January 2020 at 08:43 PM. |
#17
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I have no qualms about using the method again because I have actual physical proof that heating up to a reasonable temperature will work and work well, so why change it? It really is a 'no brainer'. As I said about B&W I only mentioned film developer. With Ilford Multigrade I used to decant a 5 litre cannister into 9 x 500cc glass bottles and the remaining 500cc were then decanted into 5 x 100cc bottles which are a convenient quantity for an evenings work in the darkroom when diluted 1-9 or even up 1-13. No heat is use because the keeping qualities in a small full bottle are very good. Last edited by John King; 23rd January 2020 at 09:46 PM. |
#18
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O-Level Chemistry to the rescue ... "Organic" just means "contains carbon". For example, engine oil is an organic compound (amongst other ingredients). No specific reason why an organic compound is susceptible to heat. As I mentioned, Ilford's ID-11 instructions are to mix at 40 degrees C so it is clearly safe at that temperature.
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