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Can I store oil paint in an airtight bottle? I read in a lot of forums that the space in the bottle (air) will dry out the oil paint. This confuses me, why can we store linseed oil in a bottle but not the oil paint?

I really need a container. I bought some affordable oil paints (100mL) but the container caps break easily, now I cover them with plastic bag and rubber band, it is messy. To purchase aluminum tube is not an option for me since they can't be purchased locally and importing them will cost more than than my paints.

  • Accepted answer sure is comprehensive but it missed an easy solution: use the bottles, fill with your oil paint and then add a thin layer of linseed oil to cover the paint and seal it from air. Voila! – rebusB Oct 6 at 20:32
  • Forgot to mention that the bottles or jars should be glass. Plastics will react, some sooner some later, with the oils and solvents in the paint, possibly with the pigments themselves. – rebusB Oct 6 at 20:48
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The problem with bottles

Oil paint doesn't really "dry", it hardens through a chemical reaction that turns the oil in the paint into a kind of plastic. The oil reacts with oxygen in the air and polymerizes.

If the paint is stored in a container with no air (like a squeezable tube), it can't start the hardening process until it's dispensed and exposed to air. If it's stored in a jar or bottle that isn't filled right to the top, the container will contain some air, and the oxygen will react with the paint. There may not be enough air for all the paint to harden initially, but it will harden as a cumulative process. The surface can skin over (which would need to be removed and discarded), and some of the paint below that could become partially polymerized, which will change its characteristics.

Every time you open the container, you exchange the air inside with fresh air, and more oxygen to react with the paint. Even if you open the container only briefly to take out some paint for use, you leave the container with fresh oxygen when you reseal it, which will react with the paint while it's in storage.

A container of just linseed oil can eventually do the same thing, but it's less susceptible. Without the paint pigment, the oil is better able to mix when you handle the container, so it has more tendency to become slightly polymerized throughout instead of the surface hardening.

Solutions

I can think of a few kinds of "adjustable" containers that would allow you to store the paint without air pockets:

  • Empty plastic lotion tubes designed for people who make their own cosmetics or want to repackage lotions for travel size. They're widely available (Google "empty lotion tubes").

  • Large plastic syringes (no needle, just a fairly large "nozzle"). It's easy to plug the nozzle hole to seal it when not in use. These are available on Amazon and other retailers. They're typically made of polyethylene and can be cleaned and reused, and 100 ml is a standard size.

  • Small, very heavy-duty resealable plastic bags/pouches that open on the narrow end. You can buy squeezable plastic pouches that are long zip-lock tubes designed to fill with juice and freeze to make popsicles, like these.

    They also sell refillable plastic "flask" pouches with a capped nozzle designed to hold and drink beverages like this. These tend to be bigger than your paint quantities, but you just squeeze out any air. Or keep the empty portion flattened as you fill the pouch so all the paint is at the open end and there is no air in the unfilled portion of the pouch.

  • Very heavy-duty plastic bags plus an accessory resealable dispenser cap. You can find these caps at places like Amazon or at big grocery stores in the gadget section. They are typically a spout with a snap-close lid plus a clamp that seals the bag around the spout. When you use up the contents, you can clean and reuse the cap. They go by various terms, but "plastic bag spout" as a search term brought up a bunch of examples on Amazon.

    You can also make your own. Cut the top off a plastic bottle that has a cap and neck with deep, continuous threads (more likely to find on a juice bottle than a soda or water bottle). Unscrew the cap and feed the opening of a very heavy-duty plastic bag through the bottle neck from the bottle side. Fold it over the threads of the neck. Then screw the cap on over the bag.

    A variation is to use the top of a plastic bottle that has a flip-top cap or other closure mechanism (like a bottle from shampoo or liquid dish detergent). The bottle should have some kind of indentation between the threaded neck and the rest of the bottle (so you can secure the bag without it pulling off). Wrap the opening of a very heavy-duty plastic bag around the indentation and use a zip tie to make a tight seal. Then you can use the cap's built-in dispenser.

  • Use a bag similar to an icing piping bag that is completely air tight (not rolled from a sheet), and that has a good sealing clip on the back and a nozzle with a sealable cap.

If you don't want to go that route and want to stick with a bottle or jar that will contain an air space, you can slow down paint hardening by displacing the air so there is no oxygen in the sealed container. Before you recap the container, squirt in a burst of "canned air" from a duster (like "Dust-Off"). The gas is propellant and an "inert" gas. Aim the nozzle at the wall of the container so the gas creates a vortex. Then immediately cap the container. This will displace most of the room air.

Another way to do this if you have access to dry ice is to drop a few very small chips of dry ice on top of the paint and lay the lid on loosely. Give the dry ice a few minutes to sublimate and displace the air, then tighten the lid. Use just a few small chips of dry ice so you don't freeze the paint. They will mostly float on a layer of carbon dioxide and sublimate quickly, and it doesn't take much to produce enough carbon dioxide to fill the top of the container.

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  • I honestly seen/thought almost all these solutions before but thank you for putting them together here which is great for other people to see. Also, providing the correct names of the materials is a big help. – dpp Oct 2 at 1:37
  • Syringe is what I will try because it is sturdy like a bottle. My only problem with it is the protruding plunger, it consumes unecessary space, I'm thinking of cutting it and have just one when I need it. I will then attach a capped nozzle with epoxy. Do you mind highlighting (make it bold maybe) the names of the materials in your answer for easy reference? Thank you. – dpp Oct 2 at 1:48
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    @dpp, a couple of thoughts for syringes. 1. You don't need to attach a separate nozzle. The syringe ends in a nozzle. You just need some form of removable cap. you can easily make one from a tip designed to attach to the syringe, a piece of soft tubing that you seal, or mold a cap out of a little silicone caulk. Syringes are usually made of polyethylene, and epoxy won't bond well with that, anyway. 2. You can get syringes with a removable pusher for the plunger. A lot of printer ink refill kits come with the ink in those. (cont'd) – fixer1234 Oct 2 at 3:28
  • If you buy syringes, they're typically a few dollars each, and you can clean and reuse them. If you cut off the plunger stem, you can find a way to push the plunger in. But it will be hard to get it out again for reuse. If it was me, I'd go with the lotion tubes. They're essentially what paint comes in, they work, they're easy to fill and use, and they're an inexpensive solution. – fixer1234 Oct 2 at 3:29
  • thanks for the heads up about polyethylene stuff, I didn't know that. Regarding the plunger problem when its empty, maybe I can install a thread or hook to pull it, I'll figure it out. I already tried one type of lotion tube with big lid and the spout and lid gets messy if you push it down the palette. I find capped nozzle appealing. I learned a lot! – dpp Oct 2 at 6:18

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