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How does the amount of crisco in water affect how water freezes?
Crisco, and other shortening products, are made of oils and other fatty
molecules called lipids. These substances do not dissolve in water and
do not change the water's properties. Crisco is lighter than water and
will float on top of it. Crisco is also a lousy thermal conductor, and
a layer of it on top of your water not only will prevent thermal
conduction, but also reduce the evaporation rate. If the top of your
water tray is entirely covered in crisco, there will be no evaporation.
Evaporation helps to cool water down quickly (but you lose some
water in the process). Your ice should be the same whether or not it
has crisco on top of it, but you may have ever so slightly more of it
and taken longer to make it if there is a layer of vegetable shortening
(published on 10/22/2007)
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