Hi, Sol! Surrounding the vessel with ice water will give a more uniform and reproducible effect, with no loss of thermal gradient. Just add more ice in case it all melts.
It seems to me you will get more convection at a lower temperature with the same amount of heat. Or, heating could be increased without increasing the temperature. (heat and temperature are not the same thing.) I will hazard a guess and say that the quality of the CS will go up. Best regards, Matthew
