Ask A Scientist General Science Archive

name         David E. G.
status       educator
age          50s

Question -   Rock salt is used for making ice cream.  We have found table salt actually lowers the 
temperature of ice water several degrees more.  Why is table salt not used?
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David,

It works quite well because it is more soluble than rock salt. It is not used much because it costs quite 
a lot more than rock salt.

Regards,
ProfHoff 669
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No reason. It "works" better because table salt is a much finer grain and so it comes to equilibrium with 
the ice/water quicker. The only "ice cream maker's" reason might be that you do not want the temperature 
to get too low. There is probably some differential in price, but both forms of salt are so inexpensive 
for home-made ice cream compared to the other ingredients, that is not an important consideration.

Vince Calder
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I am not by any means an expert on making ice cream, but I am willing to make a guess.  If it is correct 
that table salt lowers the temperature even more, the water might freeze faster and create ice crystals in 
the ice cream.  I doubt most people want gritty ice cream.  You could try an experiment--try one batch with 
table salt and one batch with rock salt and see what happens.

Pat Rowe
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Rock salt is cheaper.

Some ice cream makers do recommend using table salt, so there is obviously no operational reason not to use 
it.  But if rock salt will suffice, using table salt in an ice cream freezer is like washing your floor 
with distilled water - too much added cost for not much added benefit.

Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
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