Re: Why do you use kosher salt rather than table salt when making ice-cream?

There are two areas in which one can 'use' salt when making ice-cream.  
Since I am not sure whether you are asking about salt as an ingredient or 
salt in the brine used during freezing, I will talk a bit about both:

Kosher salt is normally used as an ingredient in ice-cream instead of 
iodized salt in order for ice-cream manufacturers to claim their product to 
be 'Kosher'.  It is a naturally iodized salt, in contrast to table salt you 
typically buy in the store, which has been chemically purified and refined 
to a more uniform grain size.  I do not know of a true compositional (aside 
from impurity level) or functional difference between kosher and table 
salts when using them as an ingredient, although I would expect the flavor 
to be slightly different between the two.

Conversely, rock salt is the salt of choice for freezing when you churn
your own ice-cream by hand.  Ice cubes and rock salt are packed around the 
exterior of the freezer barrel, creating a cold brine solution.  The brine 
keeps the freezer barrel uniformly cold and improves heat transfer between 
the ice and the ice-cream mix.  I don't use table salt as a substitute 
because it is more expensive than rock salt and the brine does not need to 
be edible.

I hope I've answered the right question for you.  Feel free to email me 
directly if you need more information about ice-cream.

Kieran