Block Ice

Nick R tell Mrs John R to try rock salt - it keeps the ice longer from melt down.

Don`t get any tucker in contact with the ice or any that has started to melt!! Your tatse buds will get that briney feeling.

Have a good break mate.

Vinnie

I think it's true...but I would rather leave them as fresh water. If you are doing the blocks in milk containers etc, when they melt, you can drink them or use the water for a lot of other things, like the wiper washer, radiator if need be...and so on.

Adding ice lowers the freezing point of the ice - which makes it colder. But it doing that it will also melt at that lower temperature, and your cooler is full of salty water.

I tried it once then went back to normal (unsalted) block ice.

Jack

adding salt does not give any more thermal mass

fresh water ice melts at 0C

salt water ice melts at a temp lower than 0C...the temp dependant on amount of salt.

Water or solution in esky increases thermal gains to ice thus melting it quicker...

So if you want ice to last longer use fesh water and keep draining the water out

G'day Nick R,
A professional fisherman I know uses rock salt on top of the ice which is then covered with a wet towel or two.
This is to retain ice in a separate esky pending later use in his main esky.
He says the ice lasts longer this way.
What I do even at home is to attach a piece of garden hose to a hose attachment the male click on part (13m) and insert that in the plug hole of esky.
By placing a paver under esky thhis drains the water progressively, which in turn reduces the melting process , as mentioned by nudenut and others.
Pedro

Thanks for the responses, I'll be freezing bottles of FRESH water, no salt, in a variety of shapes to aid packing, at least if i get thirsty i can drink it!!! I have had salty beer, not that pleasant.
See ya on the track,
NickR

Freezing salt water will definitely give you a colder esky. Salted ice melts at a lower temperature. What I did once was prepare a layer of block ice for the bottom out of saltwater. On top of this I put normal feshwater ice. As the warmer freshwater ice melted, it dribbled on the saltwater blocks and refroze. Take it from me, I'm a chemist.
Watch out though. Saltwater in your car is not a good thing, is it really worth it?
I did my trick on a fishing trip so no worries about leakage or whatever but I wouldn't do it if the esky was in a car. A mate of mine checked out a ute for sale that had rust in one corner of the tray from this.
Hope this helps.
Cheers, Mark
PS as for how much, experiment. Dissolve as much as you can in normal temp water and see if your home freezer can freeze it. Sometimes it takes several days to freeze. If it does, you're on a winner.

Interesting point there,
There is a bit to esky management, got a mate who rafted the colorado river, in the grand canyon, on day 30 they still had a little ice, I think they did get 1 delivery, not sure. they emptied them 1 at a time and always kept transferring what ice they had left to where it could be useful. the water would have been drained off and when they set up camp they would put them in the shade with wet towells and stuff over them, so it can be done.
NickR