Random House issued a recall of a cookbook, Woman's Day Crockery Cuisine
, after realizing that one of the recipes "could cause a serious explosion."
The recipe in question was for "Silky Caramel Slices." The problem was that it instructed people to heat an unopened can of condensed milk in a crockpot for four hours. A statement from Random House noted, "If the recipe is followed, the condensed milk can could explode and shatter the lid and liner of the crockery cooker."
What the recipe neglected to mention was that you should add water into the crockpot surrounding the can. Initially I thought you should open the can also, but my wife (who's heard of this technique of cooking condensed milk on a stove top) corrected me. You keep the can closed so that the milk doesn't boil out of the can.
Marilynn Marter, writing in the Chicago Tribune
(May 25, 1978) explains:
The recipe in question was for Silky Caramel Slices and called for heating a can of sweetened condensed milk in a crockpot. Because of an unfortunately elusive line that should have instructed folks to fill the pot with water, following the recipe appears to have resulted in some unintentional pop-top cans and badly damaged crockpots...
The conditions that have made this underground recipe successful and therefore popular, especially with children, are water and temperature. By being heated in boiling water, the temperature of the can and milk do not exceed the boiling point. After a few hours of this, the sugared milk turns to a caramel pudding. In the Crockpot, however, especially without water, the temperature can build up rather like a pressure cooker. That was the most immediate cause of the problem.
The 'exploding' recipe (Silky Caramel Slices) is listed third from bottom, right-hand column.
The Tennessean - May 9, 1978