Wikipedia:Reference desk/Archives/Science/2023 August 6

= August 6 =

When to stop using a can of deodorant
Is it a waste to stop using a can of deodorant before it runs out? Someone told me that a significant proportion of a can is propellant rather than the fragrance and once you get down to the last 1/5th or so of a can you should stop using it as only the propellant is left and the fragrance has mostly gone. Is this correct or complete nonsense? Does it make a difference if you shake the can before each use?

A bit of googling and a look at the wiki page on aerosol cans hasn't really helped me. Many thanks in advance.

This is NOT a troll post or a request to ask for information on how to dispose of aerosol cans! 51.9.13.201 (talk) 13:23, 6 August 2023 (UTC)
 * The propellant/deodorant mixture is homogenous. Otherwise, it will be easy to see phenomena like lack of deodorant after the can was stored for some time, and even more pronounced if the can was stored upside down. You see such behavior in spray paint cans, where the mixture is not homogenous - but not with deodorants. In conclusion, this rumor you heard is likely to be poppycock. Zarnivop (talk) 13:40, 6 August 2023 (UTC)
 * The aerosol that comes out of my aerosol can is not so much a homogenous mixture as a cloud of liquid drops suspended in the propellant gas. I think the OP refers to the liquid as "the fragrance" though it can be an odourless chemical such as aluminum chlorohydrate. A typical propellant gas is propane. The first sign of exhaustion of an aerosol can having non-miscible contents may be a change in "hiss" sound as it emits propellant alone. At this point the OP may enjoy a little more fragrance by rotating the can so that its internal pickup tube reaches the lowest corner; not to try this would be a waste. Philvoids (talk) 19:53, 7 August 2023 (UTC)