Fibreglass - the clue's in the name...

I've been working on the King costume this last two days and one of the main parts is a fibreglass bulldog, representing Britain. I have never had to work with fibreglass before and for some reason it hadn't occurred to me that fibreglass might have some properties of glass.

Like the fact that it IS glass.

That goes some way to explaining why I have glass splinters in my hands tonight then...