> A CO2 canister output pressure changes with temperature and volume
Temperature yes, volume, not really. The CO2 is in liquid state, maintaining its vapour pressure. Although if the starting volume is low, then the liquid could substantially cool down during the extraction and lower the vapour pressure that way.
All of this is irrelevant though, as the pressure is regulated down to espresso extraction levels during the extraction. It looks like it's done by hand by eyeballing the pressure gauge, pretty wild.
Also not much CO2 enters into a hot liquid, CO2 solubility is drastically down at this temp, as the article notes.
Temperature yes, volume, not really. The CO2 is in liquid state, maintaining its vapour pressure. Although if the starting volume is low, then the liquid could substantially cool down during the extraction and lower the vapour pressure that way.
All of this is irrelevant though, as the pressure is regulated down to espresso extraction levels during the extraction. It looks like it's done by hand by eyeballing the pressure gauge, pretty wild.
Also not much CO2 enters into a hot liquid, CO2 solubility is drastically down at this temp, as the article notes.