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