16 Feb Hot Knife

While insulation foam is a great option for creating backdrops and other elements of a set; cutting it into desired shapes can be tedious. We’ve found that a hot knife is the best option for carving shapes, letters and other curved pieces of the set. If you are looking for a straight, clean cut then it is best to cut with a sharp utility knife.

NOTE: You cannot use a hot knife on craft foam core because it will burn the paper that is attached to it. A sharp utility knife will work for craft foam core. In addition, when carving insulation foam with a hot knife, a respiratory mask should be worn to avoid inhaling toxic fumes.

Here is an example of the process we use to create set elements that require a hot knife:

Projected image onto insulation foam







Carving the image







Painting the image

  • Sue Coker Mathis

    We’re wanting to purchase a hot knife but there are lots of choices, ranging in price from $35-$250. Any advice?

    • Lisa Molite

      Hi there. Thanks for getting in touch! The hot knife we have is the one pictured in the photo above (I linked it below as well). We bought it several years ago and it cost about $100. It has been great for us and is still going. I will say – it is for very simplistic cutting. If you are looking for more detailed, precision cuts, you’ll want to invest in one that has more of a wire than a blade – so you can make curves and angles. Our edges don’t look too great when cutting curves, circles, etc… but from a distance (on our backdrop, etc.) it works out fine. We did find one hot knife that can cut through craft foam (the kind with the paper on it). The one pictured above will burn craft foam in seconds (like literal fire on the paper!) but is great for large items cut from insulation foam. The other we have (that we use for the paper covered craft foam) looks like an X-acto knife that you plug in and was pretty cheap ($19.99 at the local craft store). Here are some links to some I would consider. Hope this helps:

      Craft Foam Cutter:

      Precision Foam Cutter (for angles, circles, and real carving):

      Our hot knife that we use all the time:


    • Lisa Molite

      One thing I forgot to say – the wire type cutters are for more detailed type of work. If most of your foam cutting will be from large sheets of insulation foam – you’ll want to go with a thicker blade, like the one I linked that we use regularly. It is fast and makes life so much easier! It can tackle larger/thicker sheets of foam as well. Let me know what you decide on and how it’s working out!

      • Sue Coker Mathis

        Great! Thanks.