i dont know what rock salt is
i wondered whether regular table salt would work
i found this:
table salt 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,
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table salt “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.
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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.