Found some square cross section plastic (fruit juice) bottles about 1 litre. Round ones don't pack as closely.

Take a cup of salt, add to one litre of water (proportionally) and fill the plastic bottles. To the very top - no air. If you squeeze the sides a little, with experience, you will work out the amount to do.

Place in bottom of Chest type Freezer.

The water will freeze, expanding the bottle slightly perhaps (glass wil shatter!). It will stay cold if the power drops out.

The salt causes the specific heat of the water to be changed so that they will stay frozen longer than plain water.

They work well in Eskys too.

DON'T Try To Drink These! I mark them with a marker pen "SALT"

Plastic softdrink bottles seep gas, losing pressure. But if you like to keep some "flat" lemonade to drink to assist with really bad upset stomachs, if it is 6 so or months old works just fine. (Old Wives Remedy)

Robin