The following is a sample of a question that I commonly get, along
with my response:

> i recently inherited an old fashion crank ice cream maker from my
> parents unfortunatly they have lost the recipe book that came with it.
> my children would like to try making ice cream in it so i pulled some of
> your recipes. the only problem i have is the ratio of rock salt to ice.
> can you give me some idea as to what this might be?
 
I have some instructions from a 1975 book.  If, BTW, you have a
White Mountain Ice Cream machine, you might want to send email
to White Mountain itself; see my "links" page for their URL.

Steve
=====
The following is from the book "The Natural Foods Ice Cream Book," by
Robert Soman, Pyramid Cookbooks, 1975, ISBN 0-515-03575-0.  I assume
it is out of print.

ICE

Get the ice ready.  Aproximately 10 pounds of ice in small sizes is needed
for a 2-quart freezer (20 lbs for 4-quart; 25 pounds for 6-quart [note:
I can't tell if this last is a typo; the salt scales linearly -- sm]).

If you are not measuring the ice by the pound, a rough guide is that
the freezing process will require approximately as much ice as will
fill the bucket without the can.

The ice should be cracked/crushed into small pieces (ice cubes may
be sufficient).

SALT

Have the salt ready.  It is a more critical element than the ice, so
measure out the required amount carefully.  (The 2-quart freezer needs
1 cup of salt, the 4-quart 2 cups, and the 6-quart 3 cups).  You may
want to use 3 separate containers.  Rock salt is preferable; however,
fine table salt may be substituted.  Just decrease the amount by 1/3.

FREEZING

Assemble your machine [I'm skimping on the instructions -- sm].  Fill
the can no more than 2/3 full to leave room for expansion.  Start the
unit turning before packing with ice and salt; it must be moving
freely.  There will be 3 evenly distributed layers of ice and salt.
The first layer is ice to a height of about one-third of the distance
between the bottom of the bucket and the drain hole.  Then evenly
sprinkle the first portion of salt over the entire surface of the ice.
Repeat this proceedure two more times.  Your third layer of salt
should come just below the drain hole in the side of the tub.  This
hole should be left open at all times for drainage of excess brine.

Pour a cup of cold water evenly over the top layer of salt (1.5 cups
for 4-quart; 2 cups for 6 quart).  The top layer of ice will move down
quickly as it starts to melt.  Add more ice to the leve of the can
cover.  After cranking for a while (15 min) the ice level will be
low and should be refilled.  The process should take 20-30 minutes.