We use a Cabela's Polar Cap Equalizer Cooler due to it's incredible ice retention. Couple that with the use of salt water ice blocks, and we have a super cool (no pun intended) way to keep all of our food the way it's supposed to be: COLD!
There is a little bit of science, and a LOT of trial and error that we went through to get to where we are now. I once saw a video on salt water vs regular water ice blocks, and it was enough to convince me to do my own tests, which supported what I found in the video. The end result is that I have salt water ice blocks in reusable containers that we use in our Cabela's cooler, and refreeze when we get home. The picture to the right is one of our salt water ice blocks after about 48 hours in the cooler. The fresh water ice block in this test was about 1/6 ice to water in comparison.
Here are some facts (Ok, you math wizzes out there, someone check my calculations on this, because I went to skool in Kentucky):
Pure water freezes at 32 degrees; salt water freezes a t a lower temperature, depending on how much salt is in the water. Here are some examples:
The thermal conductivity of water is much higher than air, meaning that air is a better insulator at keeping the outside temperature where it needs to be. Outside my cooler. My thought process is that if having water in contact with the inside of the box would increase the flow/transfer of heat through the walls of the box into the interior contents, it would therefore be conducive to not have any water in the cooler, which would further slow the thermal transfer of heat into the cooler, prolonging the desired cooling effect of the contents. I don't like soggy anything in my cooler, but I don't like salty soggy anything in my cooler either. So, that's one of the reasons why we use containers for our salt blocks.
So, here's what we found that works for us. On the outside:
And on the inside:
One last thing. We use POPCORN salt because it also turns the water yellow, so that we can tell them apart!
UPDATE: We used these salt water Ice Blocks on our Grand Canyon Trip. I packed the pre-chilled cooler on Sunday at 2PM. On FRIDAY the bacon still had ice crystals on it, but it wasn’t completely frozen. We expected it to thaw, but we did not expect Ice crystals! All in all our system worked very well on our trip, although we had one block that melted quicker than the other. We were very pleased with the outcome!