Making ice

[thrillseeker1]

I have about 10 large flat freezer blocks I picked up at Bunnings at $2 each. They are filled with salt brine so defrost at about -2oC. I sometimes add a bit of saltwater to make a slurry but normally just bury the fish under the freezer blocks. I also make 4L icecream containers of salt water for bigger trips. These take over a week to get nice and cold. When they melt they don't dilute the slurry

That would be true if the salt ice froze homogeniously but that's not actually what happens.

Salt water(3.5% NaCl) starts to freeze at roughly -2C and in a container, freezes from the outside in. The ice is fresh water(it's one method of desalination)with the residual, a more concentrated brine liquid pushed to the inside of the block.
As the temperature drops, the brine gives up more fresh ice and becomes more concentrated until -21C where everything freezes.
Below -2C, the brine is held in liquid pockets inside the fresh water ice, the exterior of the ice block is fresh water with a melting point of 0C.
The block has to completely melt to release all the salt.

[thrillseeker1]

To summarize,
Salt water frozen in sealed bottles is inferior to fresh water, as a coolant and a big pain in the'A' if it's spilled.
Sea water added to the esky along with frozen bottles(of any ice) will almost never go below 0C.
The killer slurry is made with sea water with added salt, mixed when it's hot, and then adding a large mass of smashed ice because the freezing process has to start again , as I explained earlier, the dynamic equilibrium has to be tipped in favour of freezing rather than melting. Not enough ice, the brine will never go below freezing and the salt water is diluted.

Freezing salt water is a waste of time.

[Marlin_Mike]

Who woulda thunk it???????????? I been putting water in old plastic drink bottles and ice cream containers and putting it in the freezer. In the morning its this hard cold solid block thing. To think there are a billion other ways to make ice. Put some water in something and freeze it.............aint rocket science is it?????????????????????????

[Volvo]

Dunno!!??, bought three aprox 25 kilo bags of good hard crushed ice for $7.50 per bag late this arvo and unless one has ample space about the house , shed or garage n unless your out regular and hard to get to good Ice I still cant justify makingn storing Ice.. and have been there , done that..Just my thoughts at present..
Mind you , had I the extra space an ice making machine might be a thought but one would want a few trips out a year to warrent one??..

[timddo]

Question. Where the he'll do you get 25kg of ice for $7.50. I want to know.