Ice failure

TonyG

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Nov 19, 2010
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Ummm, adding salt to ice doesn’t do anything to the temperature. It lowers the freezing point, which allows it to be liquid at the same temperature that it had been frozen before salting. A salty slush can be 20° and liquid. Being liquid, it transfers heat away from the tuna much faster, leading to colder fish. Keep in mind that it also leads to a faster transfer of heat from the sides if he fish box.

Add enough salt and you can freeze the tuna!
That is not true. Salt.added to ice reduces the temperature. Measure it. With the right mixture you hit the eutectic temperature of the mix which is -21 C.

Google "temperature of salt ice mixture"
 
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Wild Bill

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Tim, I am not sure where you were going with that first sentence either. You went on to say you can freeze tuna with the right slurry mixture. How is that not changing temp? Inquiring minds and all.
 

TonyG

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Tim, I am not sure where you were going with that first sentence either. You went on to say you can freeze tuna with the right slurry mixture. How is that not changing temp? Inquiring minds and all.
It is a collision between belief and science. Science wins.
 
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TonyG

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This is confusing. I'm just going to buy colder ice and than you guys.
You can indeed get much colder ice than just at freezing. That helps a tiny bit. But the cooling power of ice is in the transition from solid to liquid and the absorption of the latent heat of fusion. So if you take really cold ice and warm it 1 degree, it sucks up just 1 calorie per gram, more or less. Not much. The transition from 0degree C ice to water sucks up 80 calories, more or less. That's huge.

Mostly speaking, it's not the cold of the ice, it's the melt transition that does the work.
 

Swede

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Just give the ice guy a 12 pack of Bud Light he gives you the cold ice. Not the warm ice from the other totes.
 
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sgwill122

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Tim was right, salt does not decrease the temperature of ice, it decreases the freezing point of water. Adding salt definitely cools your fish faster assuming you have ice that is significantly below 32 degrees. If your ice is at or very near 32 degrees salt will do almost nothing.
If you use 20 degree ice on your fish the ice absorbs heat from the fish and begins melting turning to water which cannot be any cooler than 32 degrees or it would be frozen. You still have solid 20 degree ice floating in 32 degree water. By adding salt the water can remain liquid at a much colder temp causing much faster temperature transfer.
So if you want to be accurate you can say adding salt to ice makes the water colder.

You can goto the link below or just read what I copy and pasted below for site with science in its name.

https://sciencing.com/adding-salt-water-make-colder-5459114.html

So how does salt (sodium chloride) make water colder? In essence, it does not. Salt works to depress the freezing point of water so the water can become colder than 32 degrees Fahrenheit (zero degrees Celsius) before it turns to ice. In fact, water containing salt can reach temperatures of nearly minus 6 degrees F. When ice cream is made, cream is placed into a canister and rotated within an ice bath. If no salt is added to the ice bath, the lowest temperature it can reach is 32 degrees F. While the cream can freeze at this temperature, it can do so more quickly at a lower temperature. When salt is added to the ice bath (usually rock salt in ice cream making), it comes into contact with the thin layer of water on the surface of the melting ice. The salt dissolves and the water becomes salty. This salt water has a lower freezing point, so the temperature of the ice bath can get even colder, thus freezing the ice cream more quickly.
 

Wild Bill

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To be accurate you would say the salt lowers the freezing point of water and also the temp at which the ice will melt. this rate increase of the melting of the ice results in the lower temps in the slurry than possible with fresh water ice with no salt added. The latent heat of melting does most of the heavy lifting as alluded to by Tony. The resulting mixture is colder than 32 and everybody knows the surface area of water vs a solid allows a much more efficient transfer of heat. How ever you want to say it that works for you is fine with me but bottom line is it gets shit colder faster.
 

Wild Bill

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I believe I also get what Tim was getting at now as I was taught the meaning of latent heat was a change in state without a corresponding change in temp.
 

TonyG

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I believe I also get what Tim was getting at now as I was taught the meaning of latent heat was a change in state without a corresponding change in temp.
Bingo. And the original post by tim was incorrectly stated.

Look up eutectic as I posted. The mixture of ice and water (pure) is around 0C (32F). Add stuff like salt or even sugar, other minerals and it depresses the stable temperature of the mixture. Ideal mixture ratios of salt/ice/water get down to -21C. Ice melts taking up energy to maintain that stable temperature (eutectic). This is also how the old ice cream makers work & how you can fuck with friends beer coolers by tossing in salt and burst their beers.

All we give a shit about is what temperature is the mixture. This is why we add salt.

When we toss in hot tuna, then the ice melts even faster in a salt/ice/water solution then it would for an ice/water solution - drawing away heat even faster than just ice/water.

Which is why people have been doing it forever.

-t
 

Salmon King

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Well, I probably incorrectly stated it but I’m a business major not a scientist.

My point was that the energy (or lack there of) of the whole thing doesn’t change when you ice it. But the water in the slurry is colder for sure.

To the OP, it is likely that saltwater got into the fish hold and melted the ice. However, it was probably a danged cold liquid that might have cooled the tuna just fine.
 

dragonballs

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All I know is everyone that has ever cut fish for us always say how cold our fish our compared to anything else. We do have an insulated hold and carry a tote of ice in that hold. We slurry and add pool salt. Also we gut and gill fish before putting in the hold. Anyone that wants to come check the temp can help on the next offload Saturday afternoon.
 

aquasport18

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Just line a walls in box with 1 inch styro foam and seal the lid with that felt material around lid then put a rubber mat bout 2 inches bigger than your lid no water gets in anmd the mat helps cool it and waterproofs the cracks better worked for me B
 

KimH

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All I know is everyone that has ever cut fish for us always say how cold our fish our compared to anything else. We do have an insulated hold and carry a tote of ice in that hold. We slurry and add pool salt. Also we gut and gill fish before putting in the hold. Anyone that wants to come check the temp can help on the next offload Saturday afternoon.
Ball park of quality of pool salt per tote? Half bag? Full bag? Couple handfuls? I can never seem to get the mixture correct.
 

wdlfbio

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About 10% salt to ice I believe, to get it to the lowest temp. Plus some water. It’s the combo of all 3. The liquid aspect eliminates all air around the fish, so you get maximum heat being pulled from the fish. This is what folks who open the belly and remove guts get such cold fish, sooner. Plus, removing the guts removes added hot material. Less to cool down.
 

FishPimpII

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About 10% salt to ice I believe, to get it to the lowest temp. Plus some water. It’s the combo of all 3. The liquid aspect eliminates all air around the fish, so you get maximum heat being pulled from the fish. This is what folks who open the belly and remove guts get such cold fish, sooner. Plus, removing the guts removes added hot material. Less to cool down.
10%??!?! Wow that’s way more salt than I would have guessed. I thought the commercial flake ice was something like 7lbs of “salt” per ton of water. Maybe I’m off by a factor of ten or 20?
I bet 10% salt ice bath is liquid at a crazy low temp. Will have to give it a extra salty shot next time. As well as removing guts/gills after bleeding.
Thanks all for the insights both experienced and scientific.
 

wdlfbio

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I think that’s to push it down to 17° or some silly low temp. I do 1-2 gallons for the 50 gallons of ice in each 1/2 tote (we don’t fill the totes full). Plus the saltwater. It gets it to 30° or less.

My damn hands hurt from the cold while cleaning the fish. And we never dug into the ice. Just grabbed the tails...

E8C2C1C3-F9F5-48E8-9C81-1389D570DD19.jpeg
 

sgwill122

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10%??!?! Wow that’s way more salt than I would have guessed. I thought the commercial flake ice was something like 7lbs of “salt” per ton of water. Maybe I’m off by a factor of ten or 20?
I bet 10% salt ice bath is liquid at a crazy low temp. Will have to give it a extra salty shot next time. As well as removing guts/gills after bleeding.
Thanks all for the insights both experienced and scientific.
To get to max cooling effect of -6F you need 23% salt by volume. Seawater is 3.2% salt and has a freezing point of 28F. You would need approximately 3.5 cups of salt per gallon of water to get it down to -6F. The temperature drop is linear as you add more salt. You need to figure out how cold your ice is to know how much value there is to adding more salt, if you have 31 degree ice there is little value. I have no idea how cold our ice is to start or once we start dumping it on fish.
 
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wdlfbio

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A 40# bag of water softener salt is $5-$6 at HD or Lowe’s and is enough for a few trips. Cheap.
 
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