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Unread 2010-10-19, 9:13   #1
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Unread 2010-10-19, 12:46   #2
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I found this there.
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Unread 2010-10-19, 13:36   #3
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Whoe does that trick with ice, salt and water really cool a beer in 3 minutes? What is the science there?

If you fully submerge a beer in ice water it gets cold pretty fast... maybe 10-15 minutes. But what does the salt do? Make the water absorb heat faster from the can?

Dr. Much... explain please.
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Unread 2010-10-19, 13:50   #4
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When you add a salt to water and the container feels cold, yes, an
endothermic reaction is taking place. The solution is grabbing heat from
the surroundings to get the salt to dissolve. When you add a salt to
a pure solvent (say, water), the freezing point will go down and the
boiling point will go up. That's because the vapor pressure of the pure
solvent is lowered (this would be easier to explain with a phase diagram).
Remember, the definition of BP is the temp at which the solution's vapor
pressure equals the external pressure. By lowering the vapor pressure,
the whole phase diagram shifts...BP to the right (higher), FP to the left
(lower). You may want to check out a intro level chemistry text or at
least draw out the phase diagram to see more clearly what gets lost is
just words here. Did you ever try boiling water without heating it?
If you have the means, hook up a vacuum to a flask of water. You don't
change the vapor pressure of the water, but you reduce the external
pressure enough so that the water does boil. Good question!
-Joe Schultz

So, more importantly, it seems we found an even faster way to chill the wort while brewing beer. Dump some rock salt in tub with the ice.

Mythbusters:

http://kwc.org/mythbusters/2005/03/m...a_sixpack.html

Final results: * Ice + water + salt: 5 minutes * Ice + water: 15 minutes * Freezer: 25 minutes * Ice: 30 minutes * Fridge: 40+ minutes
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Unread 2010-10-19, 14:01   #5
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Now that is mythbusters information that I can put to use! We should definitely do the salt in the icebath trick. I was even thinking previously of having a two stage wort chiller... where we get another coil of copper tubing and put that in an ice bath in a cooler, then run a hose from that to the coil that is immersed in the wort. So when the water is getting to the wort, it is icy cold as opposed to the temp that it comes out of the faucet. I have been bothered by this cooldown time in our recent batches. Over an hour is not good.


This is reminding me that we are due to brew a batch of beer.
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Unread 2010-10-19, 14:09   #6
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Unread 2010-10-19, 14:19   #7
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Yea was that out loud?
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Unread 2010-10-19, 14:28   #8
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I do agree though, this is totally useful knowledge.
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Unread 2010-10-19, 15:58   #9
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Did you ever make "coffee can ice cream"? we did this in 7th grade science. It's built on this principle. In a small metal coffee can, you put the milk and sugar and whatever then seal it up. Put that inside a big coffee can with ice and salt and seal that one up. Then you just have to roll the can around for a while and since it gets much colder with the added salt, the ice cream freezes in about 30 minutes.

Fun "experiment" to do with your kids if you got 'em.
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Unread 2010-10-19, 19:55   #10
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What, no one comments on how to get Free porn on a Nokia tv system?
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Unread 2010-10-19, 20:01   #11
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Quote:
Originally Posted by Domestic Goddess View Post
What, no one comments on how to get Free porn on a Nokia tv system?
Two smilies,
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Unread 2010-10-23, 19:33   #12
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Glad you guys found an answer while I was out. Just a pointer, a salt water ice bath can get the cooling temperature down to around -20 C. But that temperature is only at the interface of the ice and water, so to make sure you are truly at the cryostat temperature (constant cold) bath, it needs to be saturated (no more salt dissolves) and packed with crushed up ice (lots of surface area). It should be more of a slushee than a liquid if you're doing it right.
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Unread 2010-10-25, 8:02   #13
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Quote:
Originally Posted by AsMuch View Post
Glad you guys found an answer while I was out. Just a pointer, a salt water ice bath can get the cooling temperature down to around -20 C. But that temperature is only at the interface of the ice and water, so to make sure you are truly at the cryostat temperature (constant cold) bath, it needs to be saturated (no more salt dissolves) and packed with crushed up ice (lots of surface area). It should be more of a slushee than a liquid if you're doing it right.
So how much salt would we need, and what kind of salt do you use? I am thinking we might try that this weekend.
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Unread 2010-10-25, 19:09   #14
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Regular table salt should be fine. Wikipedia says the solubility of sodium chloride is about 350 g/L so realistically you need quite a bit for a saturated solution. If I use a saturated solution of something in the lab, I never try to figure it out, I just keep adding the salt until there's a pile that won't disappear at the bottom. That's technically the definition of saturated. It should get you to -20 C or so. Don't worry about getting the slushee consistency for what you are doing. It would be difficult at the volumes you need, just keep packing with ice.

I just found a bath to get you to -40 C/F. Calcium chloride in water does that. I believe most "concrete friendly" deicing salts are calcium chloride.

Reference:
http://en.m.wikipedia.org/wiki/Cooli...edirected=true
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