Calcium sulfate an unusual property: when mixed with water at normal (ambient) temperatures, it quickly reverts chemically to the preferred dihydrate form, while physically "setting" to form a rigid and relatively strong gypsum crystal lattice: This reaction is exothermic and is responsible for the ease with which gypsum can be cast into various shapes including sheets (for drywall), sticks (for blackboard chalk), and molds (to immobilize broken bones, or for metal casting). Mixed with polymers, it has been used as a bone repair cement. Small amounts of calcined gypsum are added to earth to create strong structures directly from cast earth, an
Simon in the Land of Chalk Drawings Simon in the Land of Chalk Drawings Simon in the Land of Chalk Drawings is a British children's animated series about the adventures of a young child named Simon, who has a magic blackboard. Things that Simon draws on the chalkboard become real in the Land of Chalk Drawings, which Simon can enter by climbing over a fence near his home with a ladder. The stories often revolve around the unintended effects that Simon's drawings have on the Land of Chalk Drawings, such as when an upset Simon draws a picture of his angry self, which goes on a rampage.