Wrenchin’ Wednesday: How to refill aerosol cans to get every last bit

Phillip Thomas

There are few buzzkills quite like grabbing an aerosol can of paint, lube, or starting fluid only to find that it’s flatter than an abandoned bottle of Coke. In those cases, for one reason or another, the propellant pressurizing the can has left the party. Sometimes it happens on its own, with the contents slowly leaking past the valve at the tip of the can. Other times, when you’re spraying but getting no fluid (say the can is too sideways or upside down), you’ll then end up with a portion of leftover product in the can with no way to spray it back out.

Over time, these inefficiencies can stack up to a waste of cash. Not only aren’t you getting the product you’ve paid for, it has the potential to stop a project in its tracks while you run up to a parts store to restock whatever secret sauce it is you’re looking to spray.

Does it have to be this way? Nope. The fix is real simple: take the can and a rubber-tipped air sprayer, and use your air compressor to repressurize the can.

Phillip Thomas

Of course, we’d really recommend safety glasses or a face shield, as there’s always a chance the product can spray out, but if you get the rubber tip of your blow gun square and work precisely it should seal up enough. You’ll want to push the nozzle of the can open while blowing air through, give or take about 10 seconds. Remember: a depressurized can starts at atmospheric pressure (about 14–15 psi), while your blow gun is backed by 100+ psi. This forces the compressed air into the can, repressurizing it, and allowing that last bit of product to be forced out when you press on the valve once again.

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    Many spray cans are using propellants that are about 70psi at 70 degrees. The cans are usually burst rated for twice their working pressure, but they’re never intended to cycle more than once, made as disposable.
    Be careful, as your can could burst and, while it’s not likely to blow your arm off or anything, the seam is the most likely point for it to fail and it WILL be sharp and make you change your pants.

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