I had not worked with shrink plastic in ages, but finding my shrink plastic sheets again I thought I'd make some experiments...
Shrink plastic consists of large flexible sheets which, when heated in an oven, shrink to small hard plates without altering their color or shape. The base material consists of thin, flexible polystyrene plastic sheets. They usually come in white, black and transparent (both frosted and shiny). Prior to heating, the plastic sheets can be colored with felt-tip pens, acrylic paint, colored pencils, permanent inks, etc. and cut into shapes.
When heated in an oven or with a heat gun, the plastic shrinks by about five-eighths and becomes thicker and more rigid, while retaining the colored design.
The colors get much richer and as you can see, from thin sheets the objects get thicker and dimensional. Amazing, isn't it?