The "tip of the week" on the current FSM home page prompted me to share how I convert 35mm film canisters to airbrush siphon jars. Sure, we all use them for paint mixing and temporary storage, along with a million other uses, etc... but here's how I make them part of my actual airbrushing setup.
During any given session, I like to swap among several different colors and though I have a couple of glass siphon jars that came with my airbrush (Paasche H), two isn't enough much of the time. Cleaning and refilling midstream is a hassle. Lots of you solve this by keeping many more glass siphon jars around for just this purpose, however, I never found a good local source for these jars (though they are readily available online through the major airbrush retailers.)
I ran into a post in another forum where somebody had converted 35mm film canisters to siphon jars by cannibalizing the siphon tube and atttachement from an "official" jar and adapting them to the plastic lid of the film canister. "Great Idea" I thought, but getting those parts alone is even harder than finding complete siphon jars.
Being one who likes to tinker, and the fact that a siphon jar is a decidedly low-tech piece of equipment, I thought I could just make my own. For my Paasche H, the fitting that slides into the base of my airbrush needle is just slightly smaller than 3/16". Just about every hobby shop in the world is going to sell lengths of 3/16" (OD) brass tubing. I cut sections of tubing about 2 3/4" long and chucked it up in my power drill. With the drill clamped in a vice, I used a flat metal file to shave away an ever-so-slightly tapered tip about 1/2" long. This is just like turning a part on a lathe. In just a couple of minutes of repeated filing (turning) and test fitting, I could get a very nice "taper fit" of the brass tube into the base of the airbrush needle.
I then put a bend in the tube so the tapered tip is about 3/4" long and just shy of a full 90 degrees relative to the long section of tubing. (See note on bending below.)
I drilled a hole in the top of a 35mm canister that is slightly smaller than 3/16" (I used 5/32'"), and a smaller 1/16" vent hole. I pushed the tube though the larger hole, it makes a reasonably secure "press fit". Voila! 5 minutes of work and maybe a $0.15 worth of brass tubing produces a very serviceable siphon jar. I cranked out 6 of these things in less than 30 minutes. I don't try to secure the tube into the lid beyond the simple friction fit because 1) it's secure enough, and 2) it makes pulling it apart trivial for cleaning.
Note: Bending the tubing without kinking can be tricky, but I happen to have a tubing bender from my collection of car tools which is intened to bend steel brake lines. RC airplane modelers (I'm sure there are a few here) have other techniques they use to bend tubing. In the end, some minor kinking is perfectly OK as long as it's not severe enough to significantly restrict the flow of paint. I've even got one that I bent purely by hand where I straightened out the kinks with a bit of light hammer work. It looks a bit crude, but works just a good as the pretty ones.
3/16" tubing is fine for my Paasche, but other brands may need other sizes. Just make sure the ID is small enough so that when you taper the tubing, there is still enough material to fit into the airbrush! ID < airbrush hole < OD