Best Ways to Cut Styrofoam With and Without Heated Tools

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There are a lot of ways to cut styrofoam and we tested all of them to tell you the best ways to cut styrofoam cleanly.

The best way to cut styrofoam is by using heated tools such as a hot knife or hot wire cutter. Heated tools will smoothly cut styrofoam without making a mess. A sharp box knife or an x-acto knife can also be used but they will become dull quickly and don´t cut quite so smoothly.

Best Ways to Cut Styrofoam

1. Hot Knife

A hot knife is an electrical knife that heats up and is mainly used for cutting styrofoam.

It cuts through styrofoam very easily and quickly without making a mess.

The heating element of the knife often runs from underneath the knife around the knife’s edge and then back under the knife.

I recommend using a hot knife with an integrated heating element and a long edge to ensure safety and versatility. A good choice is the hot knife from Dominox. You can check the price right here on Amazon.

This means you have to be very careful when using the hot knife so that you don´t burn yourself or the styrofoam.

It takes some getting used to using a hot knife because you have to hold the knife at a very steep angle to ensure that the heating element does not accidentally touch the styrofoam when you cut it.

How to Use a Hot Knife

A hot knife is fairly easy to use. Most hot knives only have an on and off button.

  1. Turn on the hot knife
  2. Wait until the knife is hot (takes 1 – 2 minutes)
  3. Place the styrofoam on a table
  4. Make sure that the part you want to cut is hanging over the edge
  5. Hold or clamp the styrofoam in place
  6. Mar the part you want to cut with a sharpie
  7. Slowly cut the styrofoam with the hot knife

When cutting the styrofoam you will quickly realize that the styrofoam melts quite quickly around the hot knife.

So you have to move quickly enough so that the styrofoam only melts as much as it needs to but slow enough so that you don´t force the knife through the material.

A perfect cut will be even, smooth, and have no discoloration.

2. Hot Wire

A hot wire is working almost the same way as a hot knife but it allows for deeper or more complicated cuts.

The hot wire is a wire that is strung between two fixtures. The wire heats up and can be used to cut styrofoam quickly and cleanly.

Here, only the wire gets how which makes it a little bit harder to burn yourself. Hot wires are also generally cheaper than hot knives.

Hot wires come in two main variants. A handheld variant and a stationary table variant.

If you want to cut foam for dioramas and your goal is to achieve a more organic shape then a handheld wire cutter is often the best choice. Something like this handheld hot wire cutter on Amazon, for example.

If you need to make clean 90° cuts then a table wire cutter is probably the best choice for you. Here is an example of a good table wire cutter with variable temperature on Amazon.

How to Use a Wire Cutter

Some wire cutters have a temperature setting. A wire cutter needs to reach a temperature of around 300°C (600°F) to cut through any type of foam smoothly. Some types of foam can be cut at 240°C (464°F) as well.

  1. Heat up the wire cutter (takes around 30 seconds)
  2. Measure and mark the cutting lines
  3. Clamp the foam down or align the foam with the wire
  4. Push the wire through the foam slowly

The wire cutter produces a much cleaner cut especially if you are cutting round shapes.

Push the wire through the styrofoam slowly and pay close attention to the way the styrofoam melts. If the styrofoam melts too much around the wire then either cut quicker or reduce the heat.

3. Sharp Box Knife

Using a sharp box knife can be quite messy if you don´t sharpen the knife after every cut.

A box knife can be used to cut styrofoam but it is quite tedious compared to using heated tools.

The styrofoam dulls the blade very quickly so it has to be sharpened after almost every cut to ensure that it cuts properly.

When the knife is too dull then the styrofoam will tear and create a huge mess that is very annoying to clean up again.

You can buy a regular box knife at your local crafts- or hardware store.

How to Use a Box Knife

You will need a box knife and some medium grit sandpaper (between 80 and 100 grit).

  1. Sharpen the knife by running the sandpaper along the edge
  2. Measure and mark the styrofoam
  3. Place the styrofoam on a cutting mat
  4. Carefully cut the styrofoam in multiple passes
  5. Repeat each step for the next cut

You can also use a knife sharpener for sharpening the boxing knife.

When I sharpen the boxing knife with sandpaper I usually place the sandpaper on the table and then run the knife edge at an angle over the sandpaper about five times.

5. Box Knife and a Candle

This is a trick I discovered recently.

You can cut styrofoam easier and a little bit cleaner when you heat up the box knife first.

Be very careful when trying this method as you can easily cut or burn yourself if you are not careful.

The basic idea is to heat up the box knife after sharpening it with the fire from a candle. The additional heat will keep the styrofoam from flying everywhere.

How to Use a Box Knife With a Candle

You will need the box knife, some sandpaper, and a candle.

  1. Sharpen the knife with the sandpaper
  2. Measure and mark the styrofoam
  3. Place the styrofoam on a cutting mat
  4. Heat up the box knife over the candle (The knife should be hot but not glowing)
  5. Carefully cut the styrofoam in multiple passes
  6. Repeat each step for the next cut

It is very important that the box knife does not get too hot or it might damage or melt the plastic enclosure that it comes in.

You only want it to be hot and not glowing red hot.

6. Guitar or Bass String

A guitar string or a bass string can also be used to cut styrofoam. The reason why I recommend this instead of dental floss is that it is easier to use and cuts styrofoam better than dental floss.

This is because of the rough surface of the bass string. You can almost saw through the styrofoam by moving the string back and forth.

This results in a much better and smoother cut than when using dental floss.

How to Use a Bass String for Cutting Styrofoam

You will need a clamp to fix the styrofoam in place while you cut it.

  1. Mark where you want to cut the styrofoam
  2. Clamp the styrofoam in place.
  3. Move the guitar or bass string up and down to cut the styrofoam

Apply a little pressure towards the direction that you want to cut in.

Cutting the styrofoam like this will make quite a mess if you don´t move the guitar string up and down enough.

How to Cut Styrofoam Without Making a Mess

The best way to cut styrofoam without making a mess is using a heated cutting tool like a hot knife or a hot wire. Styrofoam will melt at around 300°C (600°F). A hot cutting tool will melt through the styrofoam instead of cutting it resulting in less of a mess.

Styrofoam will always make at least a little mess when cutting it so the only way to avoid making a mess is by melting through it instead.

I personally recommend either using a hot knife or a hot wire for cutting styrofoam.

For hobbyists, a hot wire is probably the best choice in most situations.

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