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Making a Clear Ice Block from the Bottom Up

6a00e553b3da2088340120a77d8b26970bNearly five years ago I figured out a method to make clear ice blocks in a picnic cooler in what we now call the Directional Freezing or Cooler Method. It works from the top-down. Now a reader has figured out a moderately easy way to freeze in a cooler from the bottom-up. 

An index to all of the ice experiments on Alcademics is here.

In the top-down method, one simply fills an insulated cooler with water and leaves the top off. The water freezes only from the top down, and all the trapped air and impurities are pushed to the bottom, where a cloudy 25% or so will form if you let it freeze that long. 

Freezing From The Bottom-Up

Commercial ice machines like the Clinebell freeze blocks of clear ice by freezing from a cold plate on the bottom, while a water pump near the surface keeps water circulating (thus preventing ice from forming on the surface). 

Reader Nome Park wrote me to tell me about a method he developed that sort of combines these two methods for the home user, producing a mini-Clinebell-type block. 

The cooler is insulated on all sides except for the bottom, and a small aquarium pump is used to keep water circulating at the top. 


The white area on the bottom is the interior of the cooler with the foam/plastic cut off so it's no longer insulated on the bottom.



  • A big freezer, like a horizontal freezer.
  • A larger cooler. He uses a Coleman 20-can Party Stacker cooler, which is taller vertically and thus best for freezing bottom-up
  • A small aquaium pump


1. Cut the cooler bottom outside layers off a few inches up from the bottom. Park did this using a Dremmel tool and a knife. *Important* You only want to cut off the outer plastic and the foam insulation. Do not cut out the interior plastic otherwise it will not hold water. 


2. Insulate the top lid. Park made a 2.5-inch thick piece of foam that fits snuggly inside the cooler (since the lids on these coolers tend not to be insulated. (Pump is just there for scale. It is not attached.)


3. Fill the cooler with water up to where the foam will hit it from the top. 

4. Hang the (unused for your fish tank) aquarium pump from the top, so that it's just beneath the surface of the water. Put the foam piece on top and the lid on that. Park cut a little section out for the pump power cord. 


5. Turn the pump on and wait for it to freeze. In Park's freezer, it takes  2 days and 2 hours to freeze (50 hours) into a block that isn't all the way frozen. If it goes too long (t 72 hours or so) the pump will freeze into the block and probably break.

6. Remove the cooler from the freezer, turn off the cord, turn the cooler upside-down, and wait for the block to slide out. (An hour is about normal). Now you're ready to cut it up. 



I asked Park if he tried this without the pump just to see what happens, but he had not tried it, basing his system on the Clinebell. 

So, for you ambitious sorts with large freezers, this might be a way to make larger blocks than with the small cooler at home. 

Thank you much to reader Nome Park who not only took the time to perfect this method but also to send me detailed description and pictures.