does anyone know how I can open or loosen a metal screw cap of a bottle of polyester resin which is stuck with the resin? Last time I used this resin was 3 months ago and I wiped the mouth of the bottle as usual. I tried to put the bottle upside down and soak the cap part in hot water, and also put the bottle in the freezer for a couple of minutes but the cap doesn't move at all. Thank you.

3 Answers 3


If the resin has completely set, you may need to break the cap or bottle to get out the remainder. However, it may just be extremely viscous, so you could try slow, steady force with a rubber band wound around the cap to get a better grip (squeezing with pliers will just break the container).

Gently heating the top in hot water may also reduce the viscosity, allowing the rubber-band trick to turn it.

There are also rubber strap-wrenches, but they might also crack the bottle, though less likely to do so than pliers.

  • Thank you DrMoishe Pippik. I heated the top part of the bottle in hot water and turned with a rubber band on but it didn't work. I ended up with cutting the bottle a bit and decanting the resin to a glass container covered with black paper to avoid sunlight. I actually tried everything I could do - put a rubber glove around the cap and placed in between door hinges and screwed, heated up the cap, using nail colour solvent around the cap, etc. The cap just warped. I will avoid buying the resin in the same type of bottle and I'll think about the solution for the future. Thank you :)
    – coyosa
    Commented Sep 1, 2015 at 0:30
  • @coyosa Remember that you could also use a non-lubricated condom like I explained here.
    – Alex
    Commented Sep 2, 2015 at 6:14

Punch a hole in it and either use the last of the product or pour the remainder into a new container.

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Or use the longest channel locks you can find and rip that sucker off.

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  • Thank you, yes I cut the bottle a bit and poured the resin to a glass container covered with black paper to avoid sunlight. That was the only solution this time.
    – coyosa
    Commented Sep 1, 2015 at 0:32

For the future, put a bit. Of Saran Wrap over the bottle top, and then screw on the closure. It will now be real easy to remove the cap.

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