Milk Jug Ice...add salt

[BucksnDucks]

Howdy Randy,
I might be a little late but just listened to your podcast from a few months ago when you talked meat care and milk jug ice. I've been using frozen jugs just as you described with the exception of using salted water. Salt water freezes at a lower temp and ice stays frozen longer. I use all sizes and really like the small square one liter water bottles.

Steve

 

[JohnCushman]

Thanks for the tip! I'll give this a try.

 

[Big Slick]

Great idea, most people forget that homemade ice cream is turned with plenty of salt.

 

[cowboy]

Howdy Randy,
I might be a little late but just listened to your podcast from a few months ago when you talked meat care and milk jug ice. I've been using frozen jugs just as you described with the exception of using salted water. Salt water freezes at a lower temp and ice stays frozen longer. I use all sizes and really like the small square one liter water bottles.

Steve

How much salt do you add, and is there a better type of salt to use over another. I'd like to try this.

 

[Big Fin]

Good point. I do know some guys use the water to drink as it melts, which would eliminate the salt option for them.

 

[RobG]

I know salted ice (which fishing boats use) can freeze meat, which you might not want. Is it an issue with bottles?

 

[Corax]

Here are some numbers on the subject (from a retired chemical engineer).

The basics: Ice keeps stuff cold because it absorbs the heat needed to melt it (latent heat) at a low temperature. Pure water freezes at 32 deg F. No surprises here.

23% salt in water will lower the melting point to about -6 deg F. Put in that much salt, and all of the ice will freeze (assuming your freezer runs that cold) and melt at that temperature. 23% salt is known as a eutectic mixture because it does not change temperature or composition on freezing.

At lower amounts of salt, the solution will start to freeze at a higher temperature, and gradually get colder as pure ice freezes out, leaving a more concentrated solution. When the last drop freezes, the temperature will be -6. If there is only a little salt in the water to start with, most of the water will freeze at close to 32 deg, and it may not be apparent that there is some concentrated salt solution lost in the ice crystals.

So if you want to take advantage of the lower temperature, put in 10 - 20% salt. More than 23% is just wasting salt.

 

[Jerky]

Sorry guys, but I don't think this helps with meat storage. Adding salt doesn't change the thermal mass, just the melting / freezing point.

A hind quarter doesn't care if it's next to a 10 degree jug of ice or a 10 degree jug of salt water.

A tub of cold salty water cools beer down faster because of the surface contact. I don't let my meat float around like that.

 

[sagebrush]

Forgive my stupid question (wait a minute, the only stupid question is the one I don't ask), to achieve a 23% salt solution, how much salt do I add to the water in a one gallon jug? I use one cooler for pre-cooked frozen entrees and frozen raw foods to keep from making a trip into town until I've been in the field 7-9 days. Be nice if I could extend the duration of my stay by keeping food frozen longer.

 

[rideold]

23% by weight is the way I understand it.

 

[vanish]

Salt water freezes at a lower temp and ice stays frozen longer.

Part A ( freezes at a lower temperature) is true. Part B ( stays frozen longer ) is false.

Part A is irrelevant here, as a normal freezer is taking them both the to same temperature.

Part B, The specific heat of salt ice is less than that of normal ice, and it will take LESS heat to melt it than normal ice.

Salt Ice's advantage comes from AFTER melting, where it takes more energy to warm it than normal water.

However, if you're getting to the water stage, there's a problem.

 

[Curvebow]

Water weight is 8.34 pounds/gallon. Therefore 1.7 pounds of salt is needed to be added to a gallon of water for a 20% solution. (8.34 x 20% or 0.2 = 1.67) For a quart bottle (1/4 of a gallon) = .42 pounds of salt to be added....

 

[Joe Hulburt]

However, if you're getting to the water stage, there's a problem.

So if your goal is to have ICE in your cooler salt gives zero advantage and could actually have a negative effect if I'm understanding correctly. Two jugs in my freezer will eventually be the exact same temp regardless of salinity level but the one with salt will turn to liquid sooner.

I'll definitely do a comparison next time I live out of a cooler for a while just to see if my logic is incorrect.

 

[hank4elk]

I like having nice cold well water to drink when a milk jug thaws.Don't drink salt water so...

I still have food & water jugs frozen in a 120qt Igloo cooler after 5-6 days of hunting in NM. Many times I have to take food out to thaw for a meal.
Shade is your coolers biggest friend in camp.

 

[BucksnDucks]

Good point. I do know some guys use the water to drink as it melts, which would eliminate the salt option for them.

Yep this can happen. A melted bottle ended up at a buddy's cabin and his guest was not real happy when he gave his whiskey a splash....ooops.
I like having a designated cooler at truck just for ice like you mentioned.

 

[BucksnDucks]

Corax, You sound like you have a pretty good handle on this. 10 to 20 seems about the sweet spot.
In my experience the ice mixture in jugs seemed to last longer, don't knowif it had any ability to cool faster. I usually hang quarters and meat then try to place in cooler with a little room for air to circulate, then jugs on top and sides.
Jugs touching meat with no bag or barrier can freeze, so don't rest your tenderloins right on the bottle.
Whether salt makes a difference or not I believe keeping the meat from sitting in melted ice makes a big difference.

 

[Corax]

How much salt to add to the water - put 2 lbs of salt in the jug then fill the jug with water.

The saltwater should stay at -6 degree the whole time it is melting, which will allow you to keep frozen food actually frozen. As noted above, you need to have enough salt/ice that it does not all melt the first day. You will certainly go through more jugs of the mix than with water ice.

 

[Corax]

Bucks Ducks - thanks. You have a good system. I have not measured but agree that the jugs will probably last longer than block or cube ice. The downside is that the food is probably slightly warmer (dry, but warmer) than with block ice. Sounds like a OK tradeoff.

I plan on using the salt method next year for frozen food instead of the dry ice I used this year.

 

[Whiptail]

Are you guys sure of the science on this one? It's been almost 30 years since I took chemistry but I *thought* adding salt to water lowers the specific heat(amount of energy it takes to heat one kilogram of a substance by 1 kelvin).

https://socratic.org/questions/how-does-salt-change-the-specific-heat-capacity-of-water

Here's a graph:

 

[COEngineer]

I like this topic. Science and hunting combined!

What I have gleaned:
1) Salt water stays at a lower temperature while it's melting (good if you want the other things in the cooler to stay colder than 32 degF)
2) Salt water absorbs less heat overall,see graph above (bad)