The Potato, Explained
My First Centrifuge, and Somewhat-Clarified Tonic Syrup

Make Perfectly Clear Ice Balls Using Insulated Mugs

You can use the Cooler/Directional Freezing method to make blocks of perfectly clear ice. But those are big blocks and many people want to make clear ice balls. 

Typical ice ball molds make ice that is cloudy in the middle. One reader developed a method to take advantage of directional freezing but it involves using a big pot of water so it's not space-efficient.

Photo 5The natural next step was to use directional freezing in a small container with an ice ball mold sitting on top.

Thus, the water in the ice ball freezes first, then the cloudy parts are pushed into the water in the insulated container below it, which continues to freeze from the top down. All the water in the ice ball should remain clear. 

I attempted this, ordering insulated mugs and coozies online, but never found one that was the right size. Thankfully, two Alcademics readers were able to find insulated containers that are just right- and send me pictures and answer all my questions. Awesomeness. 


Stainless Steel Tumbler

The one that seems easiest was sent in by reader Doug Elder. He found this stainless steel tumbler that a single ice ball mold sits in. 

Photo 2-2

He says: 

  •  The hole in the mold must be pointed down at an angle. With the hole straight down, you end up with a clear ice "egg" instead.
  •  I fill the cups to the brim and gently wedge the molds into the cup with a finger over the hole until the hole is under the water. Do this over the sink and the overflow runs down the drain. I keep as much water in the cup as possible, so there is water visible around the edge of the mold. 
  • There is no problem getting the mold out of the cup. I usually give it 24 hours to freeze and there will be an inch or two usable puck of clear ice under the mold. I'll run a little tap water on the outside of the cup and around the inside edge to loosen up the belt of ice holding the mold in the cup. This doesn't crack the balls. 
  •  At 12 or 13 hours the sphere is only 80% frozen, but probably more clear than at the 24 hour point. 

 Update: In this post, I attempted and was successful at replicating this method. It works great!



Update: Mike Laine (see in comments below) found a smaller insulated mug to use: the Funtainer. This takes up less space in the freezer than the full-sized mug. He also poked a hole in the bottom of the ice ball mold for easier filling. See his post here.





Plastic Mug with a Stand

Reader James Carroll found another way that works. He found a plastic coffee mug. The ice ball mold sits on a smaller container inside the mug. 

He found the plastic, 16-ounce mug at Walmart, but it is also here on the manufacturers website. The smaller container is a small Rubbermaid container that fits inside it. 



  • Put container in mug.  Fill mug and container with water up to the brim of mug.
  • Fill silicone sphere mold completely with water. Put your index finger on the fill hole of the mold, turn upside down, and plunge into the mug.  Do this in the sink since the water in the mug will overflow.
  • So now you have the filled sphere mold sitting upside down on the filled container, inside the filled mug. If you freeze it like this, you will wind up with a clear egg.  Because the freezing water around the sides of the mold will squeeze the mold out of shape.
  • To get an ice sphere, use a straw to suck out the water in the mug until the water level in the mug is just below the rim of the container.
  • Takes about 20-24 hours to fully freeze.  You also get a cloudy big ice cube from the container.


Thank you so much Alcademics readers James Carroll and Doug Elder for being more diligent in solving the clear ice ball problem than I was! 

An index of all the ice experiments including best successes and many failures is here


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I just tried this, and it mostly works. I think I have a problem with the travel mug I was using. That's an easy fix though (too much of the mold was above the rim of the mug, meaning that freezing was occurring from more areas than just top down.

Any suggestions on how full to make the mold? The mold separated quite a bit during freezing (maybe 1 - 1.5 cm), significantly more than when I put the mold in the freezer flat.


It is actually fine (maybe preferable) for almost all of the sphere mold to be out of the water and directly exposed to the cold air. It you look at the original version that was done with a big pot of water, 95% of the sphere mold was exposed to the cold air. The key thing is just for the water under the exit hole of the mold to be unfrozen so that the air can be pushed out of the mold.

The mold should be 110% full of water. If it isn't completely full, you will get less than a perfect sphere. One reason why reason why the mold separates is because the water surrounding the mold is too high. When that outside water freezes, it squeezes the mold out of shape causing an egg rather than a sphere.

If the exit hole is just barely under water, you will get a perfect sphere. Any excess water will get pushed out of the mold (along with the air bubbles).

Brian Kenyon

Can you show pictures of what the ice ball looks like with the water levels? Im having trouble envisioning it.


The original "Belon" method pictures illustrate. Only the very bottom of the mold is under water. Since the sides of the mold are out of the water, they don't get squeezed out of shape when the water outside the mold freezes and expands.

Camper English

Yes - And just to add to this, one reader was having trouble as his freezer is very cold. So he had the ice ball nearly totally out of the water but it was freezing so fast that it froze the ice ball from the outside-in so fast and blocked the hole on the bottom of the mold. Perhaps in this case it would actually be preferable to have the ice ball mold lower into the water.

Camper English

As JC says below, a good illustration is here:

The only difference is that instead of a big pot of water, it's a small insulated mug around the ice ball.

Mike Laine

I have found that a film of plastic wrap over the raised ball mold and container adds a trapped air insulation. The side of the mold and top of the exposed water directionally freezes second to the top of the ball. When using an insulated cup, vacuum thermos, or double insulated container I get good results. I keep my freezer at zero degrees which makes it difficult to get a clear ball but the plastic wrap slows the freeze just enough to get clarity with bottled water since the initial freeze point is on the exact top to the inverted ball mold and the plastic wrap is in direct contact. I also use a 1 1/2" piece of PVC spacer long enough to raise the ball above the lip of the container. I also design slots only at the bottom of the PVC to release frozen water pressure from the mold. I appreciate all the pioneer work you have done. The clear ice balls are fabulous!

Mike Laine

Camper English

Sounds like a good trick, thanks!

Mike Laine

I put together a few of my experiments on a website available below. Using plastic wrap or bubble wrap seems to work the best for me at 0 - 8 degrees F.

Camper English

Nice! Glad you got it figured out.


I tried this method and got really good results, other than some small air bubbles (think ball of ballpoint pen) that form in the center vertically as the ice forms. Does anyone know of a way to remove these?

Camper English

Typically when I see lines of bubbles it's due to either 1. There being a bunch of air still in the container (ball) - I suggest filling it not from the sink (with its aerator) but from a pitcher like a Britta so there is less air in the water, or 2. Jostling/movement. If you open the freezer door a lot and it shakes the container, this tends to create lines of bubbles. Good luck!


Thank you for the help, I put a new round in there last night and took it out this morning to find the best ice I've made. I'll be honest, it never occured that my sink had an aerator! This website is awesome.

Camper English


Mike Laine

Hi Camper ..... I have had to change my iceball experiment website. The address is now . You don't provide edit opportunity. Can you please change the addresses on my posts to this one for your readers? Thanks .... Mike

Camper English

Mike - Unfortunately I cannot edit comments, only leave them or delete them. Hopefully readers will see this update - actually I'll update this post with a link to your page. Great update and work identifying the Funtainer as a small-sized version of the thermos!


1) Thanks so much for your site! I have learned a ton on here and really appreciate it. 2) I found a way to make clear ice balls that I think is easier. You can find a description/pictures below. It essentially just uses some plastic ice ball molds floating in an igloo container full of water. You have to chisel them out afterwards but you can make a bunch at once and I like plastic much more than silicone.

Camper English

Awesome, thanks. Would you mind if I steal an image from your page to include in this post with a link to your site?


My ice balls are SOOOO much simpler to make but, perhaps, not quite as perfect as yours. I bought a six-ball plastic tray. I filled the top of the tray with just enough spray foam insulation to expand to the top of the sphere BUT NOT COVER THE HOLE. I sprayed just enough insulation foam on the exterior underside of the bottom tray to cover ONLY HALF of the sphere. In other words, when the trays are filled and put together, all parts of the mold are insulated EXCEPT THE BOTTOM HALF OF THE MOLD. My balls freeze from the bottom up. I put the mold into a plastic bag to catch any water pushed out, which is very little. I also cut out some foam on each end to use a c-clamp to keep the freezing water from pushing the top and bottom apart. I lay a folded hand towel on top of the mold to slow the freezing of the pushed out water.
Once you insulate your tray it can be used over and over. If your spray foam insulation OVER expands covering too much of the bottom or top (holes), you can EASILY trim it off with a paring knife.

Camper English

Thanks for the tip!

Clear balls

Howdy everyone. I am using an insulated mug approach and need help. My Ice Balls (i'm using the death star silicone mold) Are crystal clear until the last 3/4 inch of the mold, then I get some bubbling. Is the cause of this the temperature of my freezer? I cant make it any warmer.


Camper English

While some people report better success with small bubbles by boiling water, I haven't found success with that.

My guess would be vibration from whatever you're sitting it on in the freezer and/or jostling in the freezer.

The other thought would be that the insulating mug isn't the right one, in that the water in there is freezing too soon; though typically that would result in cloudy ice on the bottom of the ice ball rather than bubbles.

Mike Palmer

The short answer is: use bottled Mountain Spring water. (Thanks to Mike Laine for that tip. I've been working on this for two years and never thought to try bottled water.)

The long answer: I emailed Camper about this very thing a few days ago! The faster that water freezes, the more sensitive to clouding it is. And it seems especially sensitive in that last quarter of a freezing sphere. You need really pure water to get perfect, clear ice spheres.

I've been using double filtered tap (city) water - 15 grains hard, no iron, run through a large charcoal filter and a Brita in the fridge - to make ice spheres for two years. I thought that would be pure enough.

I can get perfect, clear spheres in a dorm fridge, set at 30 degrees. But that takes 36 hours. I've never been able to get perfect, clear spheres in our prosumer zero degree freezer - until now. It's always that last quarter that tends to cloud. (I also tried softened tap water. No joy.)

Now, part of my problem was that, until recently, my rig wasn't quite right. It has to be insulated really well, so that cold air impinges only on the top of your mold. Here's the test: When you pull a sphere out prematurely, is the bottom of the unfrozen sphere mostly flat? Or does it "cone in" to the center of the sphere? (Unlike an ice cube, which tends to freeze linearly, a sphere, having a non-uniform mass distribution, tends to freeze non-linearly, with the inside bottom freezing last.)

If the sphere is coning in significantly, then that means that your insulation isn't good enough. Cold air is freezing the sphere from the sides. This makes the clouding worse. You need more insulation around the sides of your mold and/or your tumbler.

I'm using a variation of Mike Laine's Funtainer. (I found a slighter cheaper Thermos brand 10 oz food container at Walmart. For some reason, 18 g, double walled, vacuum insulated "thermoses" have suddenly become cheap to make in China. They weren't available two years ago when I started these experiments.)

I snug the food container half way down in a giant spray-foam filled rig I made. I use double hole'd molds. I put the molds right side up, so that the thicker part is at the bottom. (To slow down freezing at the bottom. Also, I have to put my mold in a baggie because my molds leak at the split line.) When I use bottled Spring water, I am able to turn out perfect, clear ice spheres in 18 hours in a zero degree freezer. So far, no other variation of tap water has worked for me.

Camper English

Thank you for this detailed information and tips!

Mike Laine

I've received many requests on how to make clear ice balls in a recreational vehicle ie. 5th wheel, trailer, motor home etc. The problem being that these vehicles are on springs and walking jiggles bubbles into the freezing ice. I have the answer. Hang the ice ball unit using a net like a hammock. Please see the bottom of my site for pictures.

Camper English

Lol that is awesome, thanks again for sharing!


Does the bottom of the ice cube mold need to be in contact with the water? If so, why?

Camper English

Yes because the hole faces the bottom and needs to drain out into the water beneath it.

Joe H

Not the cheapest option I admit but nonetheless an option:

Click the shop link for different product options.


Any trick to get clear speheres using the Trovolo round ice molds?

Camper English

Hi - I tried to comment on the other page but it didn't work. I would try a set-up like this:

and set your tovolo ice ball trays at the surface. They make several models so I'm not sure which ones you have.


Hi -- I've been trying to make clear spheres using a "Crystal Clear Ice Ball Maker" from Alchemy Bar Goods. My spheres come out clear on the outside by have numerous streaks inside that extend from top to bottom. The streaks look a lot like they're composed of tiny bubbles.

I've been using hot (distilled) water. I fill and assemble the kit as directed and leave it in the freezer for 24-26 hours. Interestingly enough, the ice that forms at the bottom of the insulated container is perfectly clear.

The freezer is set to 0.

FWIW, I've also tried a variation on the wire loop method using Tovolo molds, which I place on a cooling rack in a pot of water. Ice spheres produced using this method look about the same as the ones I get from the Bar Alchemy kit.

Any suggestions?

Camper English

I find that streams of bubbles are often caused by vibration that knock some air loose. Opening/closing the freezer door, moving the container once it's freezing, etc. are often the cause. Or just a freezer that vibrates a bit when the compressor comes on.

Michael Scott

What does Chuck mean when he says "hot (distilled) water"?

I've heard that regular bottled, distilled water (cold) freezes clear.
Does it? And does it taste ok?

Also, any reason why a Styrofoam coffee cup wouldn't work as the "insulated mug"?

Camper English

@Michael Scott - Distilled water doesn't work. You might want to start at the overviews here:

Nothing wrong with styrofoam cups if they insulate well enough!

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