Be sure to refill by weight. Buy a full screw top canister and weigh it with a kitchen scale, note the weight in grams, write it on the can and in your phone.
Then later, when it’s empty, put it in the freezer for several minutes, pull it out and refill it with the other canister, but only fill it to the weight it was originally at. It will gladly take more gas, but there will be less headroom or no headroom, and the canister has a high chance of exploding.
The Internet will tell you not to do it, and how unsafe it is, how the valves aren’t meant for that many uses, and it’s definitely gonna explode etc etc. But if you do it smart, you’re fine. And don’t reuse the same screw canister many many times, you’re already saving money, reuse it a few times then recycle it and start over.
Also NEVER EVER EVER refill them with any amount of propane! Yes the normal canisters come with a percent of propane in them to help in cold weather. But getting the partial pressure mixture right is almost impossible at home, and propane will definitely make your canister explode. It’s vapor pressure is too high. That’s why the pure butane canisters are so thin, and the green pure propane canisters are so thick and heavy, because they need to be to hold back the pressure.
I was wondering how you’d get it past the point where it’s just equal pressure to the other cannister; I assume that’s the reason for freezing the one being refilled, and I’m guessing the cannister that’s being refilled needs to be a smaller than the one that it’s refilling from?
You’re welcome!
Well it’s more complicated than that, and I’ll be honest I don’t THOROUGHLY understand everything about it.
But the idea is to move the liquid from one canister to the other, that’s why the “giving” canister is upside down. But because you’re moving the liquid itself, you can accidentally fill the entire canister with liquid, no room for the vapor to expand into when it gets warm, and boom! So be careful. As long as you weigh it you’ll be safe 👍 You freeze the receiving can because cold gas has a lower vapor pressure. And you can put the giving can in a bowl of warm (not hot!) water to increase it’s pressure and make the transfer happen faster. You’ll feel the giving can get cold as you fill the bottom can.
Fun fact, this is how air conditioners work! Take any gas (preferably not flammable, but that exists too), decompress it in a pipe so it boils into a vapor and absorbs a bunch of heat, making the pipe cold and you can blow air over it to cool your house or fridge.
Then that boiled gas vapor goes into a compressor that increases the pressure in a second pipe, enough that the gas has no choice but to condense into a liquid again. This releases all the heat that was captured in the boiling phase. Now you’ve got a hot pipe, and you put it outside and blow air over it to cool it off, further liquifying it. Then you take the liquid and release it back into the low pressure boiling pipe inside and start the process all over again!
How do you refill the screw mount canisters from the other sort?
A special adapter from Amazon, like $20.
Be sure to refill by weight. Buy a full screw top canister and weigh it with a kitchen scale, note the weight in grams, write it on the can and in your phone.
Then later, when it’s empty, put it in the freezer for several minutes, pull it out and refill it with the other canister, but only fill it to the weight it was originally at. It will gladly take more gas, but there will be less headroom or no headroom, and the canister has a high chance of exploding.
The Internet will tell you not to do it, and how unsafe it is, how the valves aren’t meant for that many uses, and it’s definitely gonna explode etc etc. But if you do it smart, you’re fine. And don’t reuse the same screw canister many many times, you’re already saving money, reuse it a few times then recycle it and start over.
Edit: this is the one I bought, it’ll do the trick. https://a.co/d/eHJDQGL
Also NEVER EVER EVER refill them with any amount of propane! Yes the normal canisters come with a percent of propane in them to help in cold weather. But getting the partial pressure mixture right is almost impossible at home, and propane will definitely make your canister explode. It’s vapor pressure is too high. That’s why the pure butane canisters are so thin, and the green pure propane canisters are so thick and heavy, because they need to be to hold back the pressure.
Wow, thank you for the very thorough write-up!
I was wondering how you’d get it past the point where it’s just equal pressure to the other cannister; I assume that’s the reason for freezing the one being refilled, and I’m guessing the cannister that’s being refilled needs to be a smaller than the one that it’s refilling from?
You’re welcome! Well it’s more complicated than that, and I’ll be honest I don’t THOROUGHLY understand everything about it.
But the idea is to move the liquid from one canister to the other, that’s why the “giving” canister is upside down. But because you’re moving the liquid itself, you can accidentally fill the entire canister with liquid, no room for the vapor to expand into when it gets warm, and boom! So be careful. As long as you weigh it you’ll be safe 👍 You freeze the receiving can because cold gas has a lower vapor pressure. And you can put the giving can in a bowl of warm (not hot!) water to increase it’s pressure and make the transfer happen faster. You’ll feel the giving can get cold as you fill the bottom can.
Fun fact, this is how air conditioners work! Take any gas (preferably not flammable, but that exists too), decompress it in a pipe so it boils into a vapor and absorbs a bunch of heat, making the pipe cold and you can blow air over it to cool your house or fridge.
Then that boiled gas vapor goes into a compressor that increases the pressure in a second pipe, enough that the gas has no choice but to condense into a liquid again. This releases all the heat that was captured in the boiling phase. Now you’ve got a hot pipe, and you put it outside and blow air over it to cool it off, further liquifying it. Then you take the liquid and release it back into the low pressure boiling pipe inside and start the process all over again!
I am using a simpler one, like this. But yours looks pretty cool, you can do screw mount to screw mount with it too, right?
Nice! I didn’t know this existed!
Yes mine does canister to canister as well 👍👍