Clare Gaylard Glass 

Good for building up a batch of twisties, also known as Zanfirico cane. The first time I saw some of these canes I couldn't deconstruct them at all, I had to see them being made. They are a lovely way of demonstrating the properties of glass, the rapidity of movement between liquid and solid states and how the glass (I tend to anthropomophise...) 'wants' to disperse itself fluidly, evenly and smoothly.