# Gas duster mystery

PuzzledMonkey
TL;DR Summary
Why does a gas duster "fizz" when put down but stop when held?
While using an ordinary gas duster (difluoroethane) to clean some electronics, I noticed something weird (see linked videos):
• After spraying the gas duster and placing it on a hard surface e.g. countertop, the can emits a fizzing noise.
• Picking up the can causes the fizzing to stop.
• The process is repeatable i.e. putting the can down starts the fizzing again. This occurs even if the can is placed down very gently.
• The duster can feels cold to touch, but not painfully so. I'd estimate the can surface temperature as between 0 and 10 C.
• Difluoroethane has a normal boiling point of -25 C, but the can is pressurized so it could be liquid inside.
• The fizzing sounds similar to a soft drink, suggesting that the contents could be liquid with some gas bubbles inside.
This is counterintuitive. If the difluoroethane is normally a cold liquid, the heat of my hand or motion of lifting it could vaporize some and cause it to bubble. But what I observe is the exact opposite: removing the hand causes fizzing, while holding the can makes the fizzing stop.

What is going on here?

Gas duster video 1
Gas duster video 2

Keith_McClary and Drakkith

## Answers and Replies

Gold Member
Is it possible that the hissing is not coming from the can per se, but from the condensation trapped under the convex base? Set the can down, trapped air escapes; lift the can up, no trapped air.

russ_watters and Keith_McClary
PuzzledMonkey
Is it possible that the hissing is not coming from the can per se, but from the condensation trapped under the convex base? Set the can down, trapped air escapes; lift the can up, no trapped air.

I tried placing the can on its side instead of vertically and sure enough, the noise went away! But this raises another question... while I have no doubt that water is condensing under the convex base, typically condensing water doesn't make the fizzing/bubbling noise that can be heard in the video. Here's a new video with the can on its side.
https://photos.app.goo.gl/ips3kutWC3hCKHFz7

Gold Member
... typically condensing water doesn't make the fizzing/bubbling noise that can be heard in the video.
I was thinking in terms of it bubbling through the imperfect seal between the can and the table.

Gold Member
This is likely due to the fact that the countertop has a much larger thermal mass and thermal conductivity to air. More heat equals more boiling. Does placing your hand on the bottom also cause the hissing sound?

BoB

Homework Helper
Gold Member
Obviously Satan is in that can!