Types
Dry, hard floral foam -- made from plastic -- is just one foam manufacturing process available to the flower and decorating industries and consumers. You can create your own foam using a liquid floral foam, as well. The benefits of the liquid product over dry and hard foam include less storage space requirements and the ability to create foam that fits any container size and shape, without having to cut the final product to fit.
Foam Ingredients
A solid plastic, in the shape of a small resin granule known as polystyrene, is the key ingredient used to make dry, hard floral foam. Additives can be included in the manufacturing process and a blowing agent is added to make the melting material foamable. Polyurethane is the main ingredient in liquid foam, along with a hardening agent.
Read more: http://www.ehow.com/info_8768943_floral-foam-making-process.html#ixzz2kLB4VgPb