# How would air pressure affect a tube of glue?

I read a post on a forum from a guy who said that when he snipped open the end of a tube of super-thin superglue, the glue squirted out and bonded his fingers.

He attributed the unexpected squirting to the glue having been packaged at a lower altitude than that at which he lived, and the disparity in air pressure causing the glue to squirt out on being released.

I would have thought that the other way round would have been more plausible … ie if the glue had been packaged at a lower air pressure initially, then the increased air pressure while opening would have caused a squirting.

That’s just a WAG of course, no doubt physicists will supply enlightenment.

I know when I lived in Santa Fe (7000-ish feet above sea level), I got in the habit of opening certain things very slowly because they were packaged and sealed at a higher air pressure.

And recently I bought a tube of sunblock near the shore in Kona, Hawaii (at sea level) and then brought it up to the top of Mauna Kea (13000 feet up), and it was like a bukakke flick when I opened it up.

Air pressure is greater at lower altitudes, ergo a tube of glue opened at an altitude higher than where it was manufactured will tend to outflow if it contains any air. If the glue is next to the nozzle and the air is somewhere else in there, then the expanding air will push the glue out.

I will note that superglue tends to be packaged in squeezable foil tubes, and it’s just as likely that the foil had been crimped enough to be squeezing the glue all by itself, even before any air pressure difference got factored in.

It’s the residual air in the package that matters. If the package is completely full of liquid, then it doesn’t matter at what altitude is was filled. If there is some air in the package, then the pressure difference matters - if the air inside is higher pressure (packaged at a lower altitude), then it will tend to force contents out when opened.

When packing for trips that involve air travel, I try to eliminate as much air as possible from toiletries (toothpaste, sunblock, etc.). The cabin and luggage compartments of commercial aircraft undergo a substantial pressure drop during the flight - they maintain a cabin pressure at cruise that is equivalent to being in open air at an altitude of 6000-8000 feet - and if those items aren’t sealed well, any air remaining in them can expand and drive the contents out into your luggage.

I live at 11,200 feet. If I buy a bag of chips at low altitude, say Denver, they sometimes burst open by the time I get home. Makes quite a pop too. It’s all about any air in the pakaging.