make crystal clear ice!
3 Steps
in this instructable I will show you how to make crystal cear ice without any special equipment! it is super easy! you will be surprised!

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## Step 1: Use filtered water!

the filtered water is much more pure and clean!
one of the things that causes the cloudiness of the ice is dust and
extra minerals in the water - the filtered water is much better for our clear ice!
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dUc0N says: Apr 27, 2012. 5:59 PM
This is also amazing for things like ice shot glasses. =-]
me says: Oct 9, 2007. 7:02 AM
when you freeze hot/warm water, it will freeze more quickly as regular cold water
Bas says: Apr 15, 2012. 12:08 AM
He means "when I boiled water and got rid of the gases that were dissolved inside, its freezing point came up to near zero it froze easier"
btcarnovale says: Jul 12, 2010. 3:32 PM
Let's do a "thought experiment". Start with two totally identical freezers. (This is a thought experiment, so they can be totally identical.) Take two identical containers. Put a sample of room temperature (let's say 70 deg F) water in one, and an equal amount of hotter (let's say 90 deg F) water in the other. Now put each of the containers in its own identical freezer. After some period of time the 90 deg water will have cooled down to 70 deg F. But in that same period of time the water that started at 70 deg F will have also cooled down. No matter what the period of time the water that started out hotter will ALWAYS BE PLAYING CATCH UP.  So it cannot ever freeze faster than the cold water.
TheChemist123 says: Jul 5, 2011. 1:32 AM
i'm guessing you didn't take chemistry when you posted this. actually, water that is 90 degrees has more energy than water at 70 degrees. for the most part, you see that this follows logic and common sense. the freezer, let's say, is at 0 degrees, just for simplicity.

now, think about diffusion, more specifically entorpy: movement of heat from a higher "concentration" source to a lower concentration source. this movement can be facilitated/sped up by larger differences in concentration.

since water at 90 degrees has a larger energy difference with a 0 degree environment than water at 70 degrees with a 0 degree environment, the water at 90 degrees will actually freeze faster, because the heat in the 90 degree water will diffuse/escape from the water much more quickly as a result of entropy.
btcarnovale says: Jul 5, 2011. 6:52 AM
The water at 90 will certainly be cooling off faster AT FIRST. But at some point the 90 degree water must be at 70 degrees.

Are you claiming that once the 90 degree water reaches 70, that it will then cool faster than water that simply started at 70?

Thought experiment:
Put 90 degree water in one freezer. Wait until it reaches 70. At that instant, you put some 70 degree water in another freezer.

Now you have two freezers, each with an identical container of 70 degree water.

What happens now? Why/how would the water in one freezer cool faster?

In my response to zmarsh below I attempted to encapsulate the above argument in a rigorous fashion. If there's an error in the math or logic, please point it out to me.

(And BTW, I was a double major math-chem until midway in my junior year at which time I realized that math was the place for me.)
tnsoftailrider says: Nov 12, 2012. 2:31 PM
LOL.Good thing you switched to math. Hot water can freeze faster than colder water under certain conditions. It is called the Mpemba Effect. Rather than write a dissertation here just take the time to Google it. It will enlighten your mind.
btcarnovale says: Nov 12, 2012. 3:32 PM
I have Googled it, and I have noted that every attempt to seriously defend it includes a lot of verbal "hand waving". The Wikipedia article says it best "There are no reliable sources that indicate exactly how to demonstrate the effect and under exactly what conditions it occurs."

If you're willing to believe in something like that, maybe we should talk about a bridge that I have for sale.
tnsoftailrider says: Nov 12, 2012. 6:26 PM
As a college professor myself (Electrical Engineering), I tend to rely on research that either supports a hypothesis or does not support it. Instead of a simple Google search do a "Google Scholar" search. It is at the top of the search page under "more." There you will find nothing but scholarly research on the subject. You will find it has been throughly researched and found to be true (hot water freezing faster than cold water) under certain conditions. The experiment has been repeated many times. BTW, the reason Wikipedia articles are not allowed in college research papers is because ANYONE can write an article or edit it without any real knowledge of the subject. I wouldn't bet the farm on the information you find at Wikipedia. However, if you would rather believe Wikipedia than Harvard, The American Physical Society, and the American Journal of Physics then that is your call.
GummiBear says: Feb 9, 2012. 5:23 AM
I know a saying that is... "Heat goes where its HOT to where its NOT"..., and because the water is hot and the water and air around it is coooold, it will leave very fast (because it has a lot of potential energy) and drop to a temp lower than the 70 degree one. Say, 60. Then they will freeze at a normal rate, and guess which one freezes first? ( I am just a 6th grader so thats all i know...)
BlueberryCheesecake says: Aug 18, 2012. 11:20 PM
Not quite. The fallacy here is that water (or anything else) doesn't cool in leaps. It doesn't cool down 30 degrees, then stops, checks its own temperature, reconsiders what speed of cooling would be apropriate, and then continues cooling at the new speed.

What it actually does is it cools down in really really tiny steps (infinitesimally small for the methematically minded). So it cools one really small step (it's not an actual step even, but it's easier to imagine if you view it as tiny tiny steps) and then cools another tiny step and so on, and the speed changes in equally extremely small steps. Now if you imagine these steps to become as small as they could possibly be you will see that the speed changes CONSTANTLY.

To sum up, once the water that was initially 90F reaches 70F it will at that point cool exactly as slowly as water that was 70F to begin with. Same with water that started at 95F or 110F or 75F, because the speed changes constantly and in tiny steps, not in big leaps and will always reach the same value at 70F.

You can imagine it a bit like the shape of a skateboard halfpipe (slow,gradual change in incline) vs stairs (flat, then a drop, then flat again and so on).
SumGie says: Aug 4, 2011. 9:23 AM
The error is that freezers have thermostats.
The compressor cycles according to the internal temperature of the freezing chamber. When you put more heat into one freezer than you do into the other, you trigger the thermostat to turn on the compressor in that freezer faster. There is hysteresis. *(did I spell that right?) in this process. The freezer puts more effort into removing heat than is needed to achieve freezing. That freezer will temporarily get colder than the other one. So the hotter water has more effort applied to removing its heat than the cooler water does. It can, therefore, indeed be frozen sooner.

If you were simply using a heat sink (such as a quantity of existing ice) to remove the heat from the water, this would not be so, but since you are using an active system, it is.
zmarsh says: Jun 29, 2011. 6:27 PM
The hot water is hotter and it will need to cool down more, but it still cools down faster. It's possible that they will both be ready at the same time
btcarnovale says: Jun 29, 2011. 11:57 PM
OK, for the sake of argument, let's assume that hot water reaches 0 C sooner than the same amount of cold water. (This eliminates having to deal with the non-linearity of crystal formation.)

so if TH is the length of time for the hot water to reach 0 C, and TC is the length of time for the cold water to reach 0 C, and DT is the difference between those times, then

TC > TH ________because the cold water takes longer to reach 0 C, and

DT = TC - TH ____DT is how much more time it takes for the cold water to reach 0 C than it took for the hot water.

But since the hot water starts out at a higher temperature than the cold water did, the hot water will at some point in its cooling reach the temperature that the cold water started at. Let's call this time D. From there, the amount of time for the hot water to reach 0 C should be equal to TC, the amount of time for the cold water to reach 0 C. At this point in time the hot water has cooled to exactly the temperature that the cold water started at so from here it should take that same amount of time to reach 0 C.

Now we can represent the amount of time for the hot water to reach 0 C as:

TH = D + TC ______Because the hot water MUST at some time go through the temperature that the cold water started at.

Now substitute the right hand side of the second equation for TH in the first equation.

DT = TC - TH

DT = TC -(D + TC)

DT = TC -D -TC

DT = -D

But DT and D CANNOT be the negative of each other because they are both positive numbers representing durations.

So TC cannot be larger than TH.

Furthermore, TC must be larger than TH, because if they were ever equal that would mean that D were 0, i.e., at some pair of hot and cold temperatures, the hot water would have to cool INSTANTANEOUSLY to the lower temperature.
grino says: Oct 14, 2011. 11:58 AM
Call me in the winter when your hot water lines burst before the cold ones . Sorry no fancy formulas just plain simple reality . I am a 3rd degree black belt in plumbing waterology have phd in turdherding. Ask any pumber or heating guy and he will tell you the same thing only in plain english . Hot water will freeze quicker than cold .
btcarnovale says: Oct 14, 2011. 2:11 PM
LOL. Good thing I spent my career doing simple things instead of plumbing.

The next time you see a picture taken by the Hubble Space Telescope, THAT was the kind of thing I did for a living until I retired. (And NO, I was not involved with the flawed optics. I worked on the spacecraft itself, not the payload.)
capt_skinny says: Sep 27, 2011. 7:32 PM
TH = D + TC ______Because the hot water MUST at some time go through the temperature that the cold water started at.

This step contains the logical leap. Yes, the hot water temp MUST at some point be equal to the initial cold water temp, but those are temperatures. It's an assumption to say that the rates of temperature change will also be equal at that point.

btcarnovale says: Sep 27, 2011. 8:59 PM
If you are going to assert that the rates of change will be different, the onus is on you to provide a reason for that to be the case.
capt_skinny says: Sep 28, 2011. 7:41 AM
I'm not asserting that the rates of change will be different. I really don't know. I'm asserting that it's an assumption to conclude they WILL be the same merely because the temperatures will be the same.
btcarnovale says: Sep 28, 2011. 8:34 AM
My assumption is based on the foundation of scientific inquiry. I.e., that two identical systems will consistently behave in the same fashion. That's why different groups will repeat experiments done by others to verify that the same result is obtained.

If you think that my assumption is unwarranted, the onus is on you to provide some reason why you think that is the case.

I also assume that the force of gravity will remain relatively constant throughout the course of my day (subject to the known variations due to irregularities in the distribution of the Earth's mass).

Would you also question that assumption? If so, why? If not, why do you question my assumption that two identical pans of water in identical freezers will freeze at the same time?

prioret says: Jul 14, 2010. 12:18 PM
Your assuming that water freezing is a Linear process. Its not. Phase changes and crystal formation are non-linear. Do a quick search on Mpemba Effect before you do your thought experiment.
kricketone says: Jul 13, 2010. 2:39 PM
well it does here hummm shot a hole in your logic .
pdub77 says: Jul 12, 2010. 7:39 AM
Not true. Anything warmer takes longer because it requires more energy and therefore more time to reach the freezing point.
qualia says: Feb 9, 2012. 10:58 PM
Not true. Anything warmer takes longer because it requires LESS energy and therefore more time to reach the freezing point. the positive energy input is applied to the freon, not the water.

just felt like contradicting someone on this glacial movement towards a eureka moment. dont take it personally.

spent three years plumbing before i decided an obligation to clear drains is not a recurrent theme i wanted in my life.
pdub77 says: Feb 10, 2012. 6:30 PM
I don't think I agree with your logic. Not about the drains, but the energy being applied to the freon. I agree with the drain part. As for the contradiction, doesn't the water require more energy and therefore the freon as well? Isn't it all in the same system with the same goal in mind? More energy applied to freon is specifically because the water is warmer and therefore requires more cooling, right?

Or do you mean that the energy (in the form of heat) must leave the warm water?
qualia says: Feb 11, 2012. 1:05 AM
Nah its just the grammar in the sentence left it open about what the subject "anything warmer" represented. I was tired, this was a featured instructable and i didnt realise the comments were this old at the time. What you meant after the above comment is now as clear as ice (the boiled kind).
pdub77 says: Feb 11, 2012. 5:34 AM
HA! Cheers, man.
prioret says: Jul 14, 2010. 12:18 PM
Look up Mpemba Effect.
pdub77 says: Jul 14, 2010. 1:19 PM
This may be true for a very specific set of variables. I will concede that. As a general rule of thermodynamics, however, I stand by my original statement. I am no scientist, though, so I could be wrong on most anything. (not that scientists couldn't be wrong either. . .) = )
zpollack says: Jul 11, 2010. 2:45 PM
i think it has to do with the spacing of the molecules. in the hot water they are more spaced out so there is more room for the cold air to come through and cool it. in the cold water the molecules are tighter and less room for the cold air to come in.
Kasm279 says: Jul 11, 2010. 12:21 PM
Longest comment tree on instructibles?
raybob says: Jul 11, 2010. 8:23 AM
From Scientific American: "It all depends on how fast the cooling occurs, and it turns out that hot water will not freeze before cold water but will freeze before lukewarm water. Water at 100 degrees C, for example, will freeze before water warmer than 60 degrees C but not before water cooler than 60 degrees C. This phenomenon is particularly evident when the surface area that cools by rapid evaporation is large compared with the amount of water involved, such as when you wash a car with hot water on a cold winter day. [For reference, look at Conceptual Physics, by Paul G. Hewitt (HarperCollins, 1993).]
Buskieboy says: Jul 11, 2010. 3:02 PM
I've tried this double boil, but used tap water so my results weren't as great. There was still a core of cloudy ice at the center. I should use filtered water, but I need cubes in hot weather so I'll make due. Although this is a great idea for parties etc. I'm fanatical about my ice cubes and I have noticed that hot water does freeze faster than luke warm, but not as fast as cool. The one thing I HAVE noticed is that hot water makes HARDER cubes and they stick more in the tray. The also shatter crack and crumble into small chips/shards too. Some cubes almost leap out by themselves, while others you have to hammer away at, or slightly warm to melt out. Weird. I think the luke warm ones are best while the really hot ones freeze too hard.
skylane says: Jul 11, 2010. 8:09 AM
This is just too funny. When I was a kid this myth was around LOL People still believe it.. LOL The simple truth is... the hotter the water, the longer it takes to cool then freeze. No matter what kind of scientific doubletalk someone tries to throw in... too funny...
mashee says: Jul 11, 2010. 5:16 PM
I thought it was funny too; the amusing part is that you're actually wrong. Your arm-chair-science loses I'm afraid. Though admittedly there's a lot of rubbish explanations to the real science behind it.
jridley says: Oct 12, 2007. 4:18 AM
No, this is an urban legend and is easily disproven. The reason it SEEMS to happen is that if you put warm/hot water in an ice tray, much of it will evaporate before reaching the same temp as the cold water, and so there is much less water to freeze at that point. Try putting equal amounts of cool and warm/hot water in a ziplock bag to prevent evaporation. The cool water will freeze first. Or you can prove to yourself that evaporation is taking place; put an equal quantity of cold and hot water into an ice tray, freeze them both (monitor speed if you wish to) then weigh the resulting cubes. The ones frozen from hot water will be lighter.
mtxe says: Oct 19, 2007. 10:54 PM
Evaporation is not likely to be much of a factor in a freezer.
jridley says: Oct 20, 2007. 8:20 AM
You're kidding, right? It's got the highest temperature differential, plus the relative humidity inside is practically zero. You'll get FAR more evaporation per minute in a freezer than you will in the average house. What makes you think you won't get evaporation in a freezer? Have you ever put a pot of hot water outside in the winter? it steams like CRAZY.
mtxe says: Oct 20, 2007. 9:17 AM
I never said "you won't get evaporation in a freezer".

"You'll get FAR more evaporation per minute in a freezer than you will in the average house."

It should evaporate at relatively the same rate(the only difference is that the water in the freezer would cool more rapidly thus reducing evaporation)

"Have you ever put a pot of hot water outside in the winter? it steams like CRAZY."
Its not evaporating more/faster.
(the "steam" isn't actually steam but rather a mist caused by the evaporating water vapor condensing back into water once it hits the cold air)
thepelton says: Feb 21, 2009. 11:20 PM
Evaporation in a Freezer is what causes Freezer Burn.
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