don’t know if this is any use in WD ( could be for someone who is close to the sea )
http://www.weather.nps.navy.mil/~psguest/polarmet/vessel/iceform2.html
when i first read the post, i thought it was refereing to a beer vessel, and to know when to stop adding ice to your beer 8O
The equation might apply to beer carrying vessels as well as ships! Perhaps you can do some experiements and report back to us. Hic!