Just a quick post to share an idea.
We fill old milk jugs with water and freeze them to use in our ice chest. If you do this, do not fill the jug all the way since the water expands when it freezes. Also leave the cap loose to allow air to escape as the water freezes.
We just recently finished a 5 liter jug of olive oil. The jug has about the same footprint as a gallon jug and fits in the ice chest standing up.
Ice tends to form on the top and works downward. This can distort a bottle even if the cap is left off. So my thought was to just put about two inches of water in the jug at a time.
Another thought came to mind. Why not add salt since salt water freezes at a lower temperature than fresh water?
So salt was added and the jug was shaken. Each time more water was added, more salt was added.
It got its first real test yesterday when we were at the farmer's market. It kept our other ice from melting throughout the day.
We also will put a couple inches of water in a plastic bottle and let it freeze and then fill with water to take with us for driving trips.
The next big test will be to see how "Mr. Salty" does on one of our shopping trips with ice cream.
jtk