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The nozzle of the spray bottle hardens quickly which makes it impossible to use after a few days and even hours.

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  • Great Stuff has a foam spray with a tip that automatically closes and claims it's good for 30 days of use. That doesn't get you 'months' of use though.
    – rtaft
    Commented Nov 28, 2022 at 16:21
  • 3
    Prepare all your jobs that need some spray foam and use up a whole can at a time ? So you're saving up the tasks, not the foam itself.
    – Criggie
    Commented Nov 28, 2022 at 18:07
  • Those cans have expiration dates. You can find old unused cans that are useless: When you shake it you can't hear anything. I've also found old unused cans where you can hear the chemicals when you shake it but the nozzle is already plugged. Trying to unplug them leads to disasters of epic proportions. Commented Nov 29, 2022 at 15:28

5 Answers 5

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You can reuse the same spray over and over simply by injecting some drop of acetone, then pour it out, and do it again 3 times to be sure nothing remains. The trick is to do it just after using it (like in a few seconds). You can then use a cotton swab to limit the exposure of the plastic with the acetone (but it evaporates quite quickly so it might not be needed).

Idem for the straw and "gun" part (the black plastic part on my picture): as soon as you stop using it, put it vertical, the gun part on the top, poor quickly some acetone on the gun, it will slowly dissolve the foam (it takes 1 or 2 minutes to reach the bottom and to exit the straw ― cf. the warning below about this solution).

enter image description here

Bonus: **by mixing 10gr of polyurethan foam with 80gr of acetone you can waterproof stuff with this water-like substance, but only if you put several layers (at least 3). A single layer isn't hydrophilic nor waterproof, but ‘breathable’. If I remember well, each layer is pierced by some tiny bubbles and thus tiny holes. So, the more layers you add, the more waterproof (but also rigid) it becomes. With this cheap stuff I waterproof my camping gears, and humid walls. Molds can't pass through several layers. (But be careful: acetone can dissolve / destroy many stuffs like some type of plastic). If needed put a layer of paint over it at least to protect it from UV, and because, if you take the cheapest foam, it'll be UV sensitive, the coating will turn yellow, then brown after a few weeks/months (which can be quite nice).

⚠ WARNING: be very careful to not touch the mix of acetone and polyurethan foam, not even with gloves as it contains isocyanates (present in the hardener or catalyst of polyurethane-based two-part paints. It will be dissolved by acetone and will easily penetrate your skin and most gloves ― I recommend applying it using a paint roller or, if you really need to touch it, using Butyl gloves, or (cheaper) 2 layers of latex gloves under some DIY gloves made out of PP plastic bags ― latex gloves will only protect you for few minutes, maybe even seconds).

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  • 2
    +1 : acetone definitely works. The "Pro" foam gun cleaner I get to clean up smells & behaves just like acetone, and I also use acetone on a rag to clean up the gun after use.
    – brhans
    Commented Nov 27, 2022 at 22:22
  • Seen on a builder's tips site a few years back: There apparently exist containers filled with a soft material that has a small hole in the center, into which a fingertip can be inserted. The bottle is them topped off with acetone. It's marketed as a nail-polish removal tool, but the tip said it was pretty darned good at cleaning the tip of pro-style foam guns. Makes sense, I guess. I haven't had reason to go looking for it so that's all I can tell you.
    – keshlam
    Commented Nov 28, 2022 at 3:11
  • Do they sell the straws separately? I upvoted for the ingeniousness but I wouldn't be trying to use that stuff without a straw on the second go-around.
    – MonkeyZeus
    Commented Nov 28, 2022 at 19:10
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    When working with acetone do not touch your glasses. Remnants on your hands or gloves will damage & breakdown the coating on the lenses and possibly the frame.
    – P2000
    Commented Nov 28, 2022 at 23:09
3

While the glue's still fresh, wet a couple of cocktails sticks or matchsticks & insert them into the nozzle & both ends of the solid part of the trigger that screws to the can's nozzle.
Cyanoacrylate is activated by water, of course, so this helps adhesion.

The flexi tube you can roll between your fingers to crack away the last use residue, or put a damp pipe-cleaner down it before it sets [you get those from craft shops these days, as no-one smokes a pipe any more;)

You then just pull all these out before next use & the residue should come with them.

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  • I'd like to correct you on one point: My across-the-street neighbor does, in fact, seem to smoke a pipe! ;)
    – FreeMan
    Commented Nov 28, 2022 at 16:45
  • Hahaha! I've not seen one 'out in public' in years.
    – Tetsujin
    Commented Nov 28, 2022 at 16:46
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You might consider upgrading to a pro foam gun:

foam gun

You would need to buy a refills, but they are usually cheaper and it will last for months because you can close the tip of the gun.

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  • 1
    The same applies for foam gun: no need to close the tips if you let acetone pass through (as soon as possible). They usually sell a "special" product to clean it: it's just acetone (just don't pour it on the plastic part)
    – JinSnow
    Commented Nov 29, 2022 at 12:51
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A little acetone will help soften up tip of the can. Then some patience and you should be able to get it clear.

You can use some Romex cable insulation as a makeshift straw. 12/2 or 14/2 seem to work best. 14/2 being the best fit of the bunch. Just cut a piece the size you need and pull out the 3 inside wires & paper leaving just the outer shell. Place that over the can tip.

-1

If you are asking about the consumer spray-can foams:

As the label on the can says, you should expect it to seal itself closed after the first use (or more specifically, a few hours after the first use). I don't know of a safe way to clear the can after this happens. If you insist on trying anyway, AT LEAST wear good safety goggles; getting a shot of this stuff in your face could eliminate your need to worry about using it again in the future.

You can reuse the screw-on nozzle/tube with some effort. Though since each can comes with a new one, it's unclear that the effort is worthwhile.

I really hate throwing out a still pressurized can, but that's what one has to do. They're cheap enough that this shouldn't be a serious problem, if you plan ahead and have multiple uses lined up for that day. Ideally, dispose of it as Hazardous Material, since someone else could do themselves harm by trying to puncture the can (see top of this note).

I don't know whether cartridges for the pro foam guns have the same self-sealing one-time-use property.

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  • The pro foam guns don't. I've used them months after last use. Commented Nov 28, 2022 at 19:46
  • Now that's a good reason to consider the investment. But the disposables are cheap, and I can usually line up enough projects to get my money's worth out of them. I just wish there was a better way to dispose of them. I've been almost tempted to rig a remotely triggered puncturing mechanism, but...
    – keshlam
    Commented Nov 28, 2022 at 20:50
  • A remote triggered puncturing mechanism would make for a fun geyser of foam, but why not just trigger the foam into a garbage bag and let it spray until it's sputtered itself out? Same result, less fun, less likelihood of danger, easier to clean up the foam mess.
    – FreeMan
    Commented Oct 17, 2023 at 13:54
  • Mostly that I don't usually think of emptying then until they've started to clog. Which is admittedly my own fault.
    – keshlam
    Commented Oct 17, 2023 at 14:19

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