- The foam curing process generates a bit of heat, so don't use on something that melts easily (e.g. chocolate).
- As the foam expands, it exerts some pressure, so don't use on something that's easily crushed (e.g. origami).
-two part polyurethane foam (available from marine supply vendors like this)
-a rectangular container (I used a plastic food storage container)
-a saw or large knife
Step 1: Wrap the Object
Step 2: Create a Cardboard Divider
It doesn't have to be perfectly centered but make sure you leave some room top and bottom so that the foam will surround your object.
Tape the cardboard into place in the container. Again, it doesn't have to be perfect, just as long as it's reasonably secure.
Step 3: Mix the Polyurethane
Note: The foam expands a lot. The stuff I have expands 16:1. I only needed about 125ml (4oz) of each component to nearly fill the container.
Stir until it starts to thicken a bit.
Step 4: Pour Foam
Step 5: Remove From Container
Step 6: Trim and Pull Apart
What you're left with should be a roughly rectangular block that holds your object securely.
This one came out a bit wonky but you get the idea.