Building prototypes and models is an essential component of any design activity. Modern product development is a multi-disciplinary effort that relies on prototyping in order to explore new ideas and test them sufficiently before they become actual products. A comprehensive modern prototyping approach is crucial to making informed design decisions, and forms a strategic part of a successful designer's toolkit.
Overall a useful resource, I think, but a couple of things don’t seem to make sense. First of all is the incessant advice to work “under supervision”, which makes absolutely no sense because if this is true then freelance industrial designers or industrial designers working alone in their own studio cannot possibly exist. Also, several materials were deemed harmful because they produce silica dust, but the author advices to use vacuuming for dust removal, which makes very little sense to someone who works with clay and taught the only safe way to removal silica dust is wet sponging/mopping.