By: Halacha Yomit team of OU KOSHER
May One Make Ice or Ices on Shabbat?
The Dovev Meisharim (siman 55) writes that changing water into ice is forbidden on Shabbat. Moreover, he writes that even if the water was placed in the freezer before Shabbat, if it freezes on Shabbat, the ice would still be forbidden because of muktza. The change in form from liquid to solid turns it into a new entity, which is muktza.
The Chelkat Yaakov (OC 128) and many other poskim disagree on both these points. Not only is ice that forms on Shabbat not muktza, but it is not clear that there is any prohibition to make ice. This is because one does not actually create ice. All one does is place water in a cold environment and the ice forms on its own. Although you may not chop ice with your hands to actively melt it into water, you may place ice in a bowl and let it melt on its own into water. The same should be allowed in reverse; water should be allowed to freeze into ice on its own.
The Chelkat Yaakov is unsure of this last point, and therefore recommends not making ice on Shabbat unless there is a pressing need.