Ti TABLE OF CONTENTS. 



Distribution of gypsum in Canada 25 



References on gypsum deposits 26 



Excavation and handling of rock gypsum 29 



Mining methods 29 



Working gypsum-earth deposits 30 



CHAPTER II. 



CHEMISTRY OF GYPSUM-BURNING. MANUFACTURE OF PLASTERS. 



Chemistry of gypsum-burning 31 



Classification of plasters 32 



Commercial classification 32 



Manufacture of plaster of Paris, "cement plaster", and wall plaster 33 



Grinding gypsum and plaster 34 



Calcining in ovens 37 



Calcining in kettles 37 



Designs of kettles 39 



Temperatures attained 44 



Actual equipment of kettle-process plants 44 



Calcining in rotary cylinders 46 



Cummer system 46 



Mannheim system 49 



Addition of retarders and accelerators 50 



Wall plaster. ... 51 



Packing weights 52 



Costs of plaster-manufacture 52 



Analyses of gypsum used in actual practice 53 



References on plaster-manufacture 55 



CHAPTER III. 



COMPOSITION, PROPERTIES, AND TESTS OF PLASTERS. 



Chemical composition of plasters 56 



Theoretical composition 56 



Actual composition of plaster of Paris 56 



Actual composition of cement plasters 56 



Physical properties and tests of plasters 57 



Weight and specific gravity 57 



Fineness of calcined plasters 58 



Tensile strength 58 



Compressive tests and effect of same 61 



Adhesive tests 62 



Rate of set and hardening 64 



Theory of the action of retarders and accelerators 64 



Materials used as retarders 64 



Effect of retarders on strength of plasters 65 



