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
Sidewalk chalk to use anamorphic drawing when drawing with sidewalk chalk. Nonanamorphic drawing are drawings that are drawn to be observed face-on, whereas anamorphic drawings are drawn to be observed from a different viewpoint. Julian Beever, in a Q&A with Adam Boretz, explained his drawing of his first anamorphic sidewalk chalk drawing, Swimming Pool: Sidewalk Sam was well known in the Boston area for his reproductions of European masterpieces, chalked or painted on the sidewalk. Sidewalk chalk Sidewalk chalk is typically large colored (and sometimes white or cream) sticks of chalk (calcium sulfate rather than rock chalk, calcium carbonate) mostly used for