The container must now be put into ice/salt water and cooled to
below 5 degrees Celsius. The easiest way to do this: take a coffee
can, put in water and salt to about half full, put container
(empty) into can, put plastic lid on can to keep container from
floating, put can in freezer, when water is frozen, take out,
remove lid, proceed. This will provide excellent cooling and also
keep container from floating.