The Complete Handbook of Craft Foam & Styrofoam

Chapter 1: Understanding Craft Foam & Styrofoam

Craft foam and Styrofoam are so common that they are easy to overlook, but the difference between a professional result and a failed project often comes down to understanding what these materials actually are. This chapter is about that foundational knowledge. It will explain the chemistry and structure of the two main material families, how they are manufactured, and why their physical properties determine what you can and cannot do with them. Before you cut your first sheet or glue your first seam for a serious project, you need to know why one foam is soft and another is rigid, why some paint melts the surface, and why a part need to be sealed before it is painted at all.

First, we need to be clear about the terms themselves. "Styrofoam" is a trademarked brand for a specific extruded polystyrene foam (XPS) made by DuPont. In common usage, it has become a generic term for all white, rigid foam, especially expanded polystyrene (EPS). This book uses the term in its broad sense to refer to rigid EPS and XPS foam, but you must know the difference in the workshop. Expanded polystyrene is the white, brittle foam that comes in large blocks and is often used for packaging and floral arrangements. It is made from tiny beads of polystyrene that are expanded with steam and fused together. Extruded polystyrene is the blue, pink, or green dense foam that is usually sold in boards for