How to Make Crystal Clear Blocks of Ice

Introduction: How to Make Crystal Clear Blocks of Ice

Do you want perfectly clear blocks of ice for use in an ice ball maker, or maybe just for fun?  Follow these instructions and have great ice in any size you want.  Only requires a few dollars worth of equipment:
Expanding insulating foam
A plastic container, such as a glass or pitcher
Plastic wrap and/or foil



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    16 Discussions

    This is really interesting. You make very nice ice slugs this way. The ball press that you made looks cool too. Was aluminum cheaper than steel? I think someone I know uses a steel ingot to make theirs and it's considerably smaller with good weight. I like the finish on yours more.

    If you ever want to see how clear ice is made professionally, find your closest ice sculpting studio and ask for a tour. They make crystal clear ice blocks bigger than you and if you need ice "slugs" for your ball maker they can make those too. It's fun to see.

    Very cool.

    Just wild thought what would happen if the bottom was left uncover and the top gets a foam cap. My thought is if freeze from bottom up, the top not lock in so you could let it all freeze bigger block and you not have come get out at the right time, not sure if it would work, I not have the time to try it right now, but later I have try to make some clear ice.

    Thanks for the posting.

    I feel like I'm missing something here. You have two plastic containers in the video, but I don't see how they are being used:

    - You spray expanding foam on the outside of the translucent plastic jug, then
    - You put the clear plastic cup inside the expanding foam.

    Are these two different configurations? Or did I miss a step regarding the two different containers? Do I put the small one inside the large one and fill the gap with foam?

    1 reply

    Apologies for the confusion! The different size containers (cup and pitcher) are indeed for two different configurations. The pitcher makes quite large blocks, while the cup makes blocks that are the perfect size for my ice ball maker.

    Whichever size you choose, you just need one, and to put the foam on the outside of that. Though if you really wanted to avoid getting foam schnibbles everywhere, you could use a nested approach.

    More recently, I have make a unit with 4 cups in a square, with foam both between them and around the outside. I can thus make 4 blocks at a time. It just barely fits in my freezer.

    would you mind posting a picture or video of what happens if you put the completed clear ice blocks back into the freezer? I want to see how much further freezing increases cloudiness

    2 replies

    Here you are.  The frosty pic is a block just out of the freezer after it had been sitting in there (in a plastic bag) for several weeks.  After 10 minutes or so, the surface melts and it looks clear, as shown in the other image.  There is no internal cloudiness.


    thanks a ton! this is super interesting and now I'm inspired to make my own clear-ice maker. Will let you know how it goes.

    While letting the water rest, you can probably shorten the rest time by having a cheap, $10 vibrating back massager sit on top (or perhaps a waterproofed vibrating massage of a shape which can fit into the cup?). This is essentially done by concrete and professional ice factories to vibrate the bubbles out.

    1 reply

    Good idea! I'll have to give that a shot.

    I did try using an ultrasonic jewelry cleaner to remove the remaining bubbles. It did in fact work well, but it's a bit tedious--right now, the process may be slow but at least it doesn't require too much human intervention. A vibrating massager thing would work well, I think.

    Thanks for sharing! I've been trying to do this for ice cubes - how would you suggest tweaking this for this smaller size?

    1 reply

    Some people say that boiling works fine for something as small as ice cubes, but I couldn't say for sure. I only know it doesn't work for the large blocks.

    I would consider using something like this to start with:

    Then, just spray the foam insulation around the sides and bottom as usual. Make sure to wrap the whole thing in plastic wrap or the like so it stays removable--you'll need to run water on the backside to remove the ice. And again, you'll need to remove the tray from the freezer before it's finished. I'd guess that 8 hours is enough for typical-size cubes (about an inch long).

    So simple since you dont have to boil water or buy distilled.

    Nice job!

    im gonna try this, but i am just gonna wrap a scarf or something around the glass and see if that insulates the bottom of the cup enough first. maybe insulate the cloth with plastic wrap to trap the warmer air inside it.

    1 reply

    Good luck! You really need quite a bit of insulation to make this work properly.

    I tried simply using an insulated mug, but it didn't insulate as well as the foam, and it was impossible to get the ice out afterward! The foam shell is nice because you can slide the container out and then run the whole thing under water.

    Let me know how your experiment turns out!