Styrofoam in a blender They are put into a blender with enough added water to float the squares near the top. Blending for about 1-2 minutes and then draining in a sieve will give you a nice Perlite substitute. It has the consistency of coarse sand, but very lightweight.
Keep this in mind if you start seeing lots of spiders around your place. Natural spider killer or preventer... take one cup of vingar, one cup of pepper, a teaspoon of oil and liquid soap. Put it into a spray bottle and spray along the outside of your outside door and along windows