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I toured a winery that used a large stainless steel tank to dispense wine. The tank had a pour spout at the bottom and a floating lid on top. I was told that paraffin oil was poured over the top of the floating lid, such that it would fill any gaps and provide an inert, air-tight top. As wine was dispensed from below, the lid simply sank with the rest of the volume.

Yes, there are many ways to store photo chemistry: accordion bottle, adding inert objects into the bottle to fill space, hell, even using a smaller bottle! I'm not interested in other methods of storage or even in the stack ranking of these methods against each other.

No, what I'd like to know is, does this method pan out with photo chemistry?

The oil should float on top just the same as with wine, but I'm not convinced of its inertness with photo chemistry.


Edit for comments:

How would you get reusable solutions back into the container without disturbing the sinking lid? It's not like you're drinking the stuff, I hope.

1 part Adonal to 2 parts lime. Float the Grand Marnier and top with soda water. I thought everyone drank these??

Because of my limited time these days, I develop once a month or two and make one-shot's of all chems needed. This process intrigued me for use with off-the-shelf chemicals for before I mix them to working strength. (I have a bottle of fix, for example, that has been between half-full and 1/8 full for almost a year now.)

Question may be a bit cleaner with a list of Specific target chemistry. - Real question is how much reaction between a given chemistry and oil can take place, as it should not actually ever come in contact with the chemistry if done properly.

See above comment. Because of my own process, I'd be keen to learn of any reactions with all steps: Developer, Stop, Fix, Perma-Wash. I don't think Photo-Flo actually goes bad so, let's not worry about that one.

  • I would assume that sodium hydroxide, which is used as pH regulator in most developers will react with paraffin oil similar to how it reacts with fatty acids. – jarnbjo Jul 29 '19 at 16:29
  • Question may be a bit cleaner with a list of Specific target chemistry. - Real question is how much reaction between a given chemistry and oil can take place, as it should not actually ever come in contact with the chemistry if done properly. [Also, just in case you missed it, 'Wine-bag' may be worth looking up.] – TheLuckless Jul 29 '19 at 16:52
  • @TheLuckless I like the wine bag idea. Would be easier to obtain and use than messing around with floating lids and paraffin. – xiota Jul 29 '19 at 17:05
  • Even if the chemicals don't react with the floating lid and paraffin, I'd expect no benefit over using glass or plastic containers, so the additional effort wouldn't be worthwhile. – xiota Jul 29 '19 at 17:10
  • @TheLuckless the wine bag looks to me like (a better) take on the accordion bottle (I can't imagine the plastic on those bottles will survive thousands of manipulations) Except now I need to make sure that I never stumble into my darkroom drunk I guess – Hueco Jul 29 '19 at 17:10
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Adding a top coat of hot liquid paraffin is in the "how to do it books" for storage of photo chemicals. I did this 50+ years ago in my home darkroom in the water heater closet. Better is adding clean marbles or using plastic storage bottles and squeezing the air out. I have used nitrogen filled bottles. I have used nitrogen filled storage tanks. I have used floating lids of paraffin. Common was polyethylene stars that floated on top in storage vats. The small star shaped hollow floats interlocked and thus reduce the air liquid junction. Many 4x5 and 8x10 hard rubber processing tanks came with hard rubber floating lids. Lots of ways to reduce evaporation and oxidation. Developer formulas all feature a preservative that retards aerial oxidation and reacts with oxidized developing agents to neutralize staining agents. Many of the other chemicals of the process also feature preservatives.

From the comments:

Please explain why the use of marbles/squeeze bottle to get the liquid up to the bottle spout (minimal oxidizing surface area) is better than a lid that brings the oxidizing surface area to 0. I could take a guess at it but I'd like to hear your perspective on it.

Protection against aerial oxidation can be a mix of things depending on the type of container and type of fluid. My mother used paraffin when canning fruit and vegetables. I used paraffin when I stored chemicals in canning jars. Marbles displace liquid bringing the fluid to the top of the bottle neck of glass storage bottles. Plastic bottles leach plasticizer depending on type of plastic and type of fluid. Bottom line, many ways to accomplish this task including switching to dry photography.

  • Please explain why the use of marbles/squeeze bottle to get the liquid up to the bottle spout (minimal oxidizing surface area) is better than a lid that brings the oxidizing surface area to 0. I could take a guess at it but I'd like to hear your perspective on it. – Hueco Jul 29 '19 at 18:49
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    @ Hueco - Protection against aerial oxidation can be a mix of things depending on the type of container and type of fluid. My mother used paraffin when canning fruit and vegetables. I used paraffin when I stored chemicals in canning jars. Marbles displace liquid bringing the fluid to the top of the bottle neck of glass storage bottles. Plastic bottles leach plasticizer depending on type of plastic and type of fluid. Bottom line, many ways to accomplish this task including switching to dry photography. – Alan Marcus Jul 29 '19 at 19:09

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