I.S. 27-1:1975

DECLARATION
1 GENERAL
  1.1 Scope
  1.2 Definitions
  1.3 Classes
  1.4 Chemical composition
  1.5 Sampling
  1.6 Testing
2 REQUIREMENTS FOR CLASS 'A' PLASTER (Plaster of Paris)
  2.1 General
  2.2 Chemical composition
  2.3 Coarse particle content
  2.4 Soundness
  2.5 Transverse strength
3 REQUIREMENTS FOR CLASS 'B' PLASTER (Retarded hemihydrate
  gypsum plaster)
  3.1 General
  3.2 Chemical composition
  3.3 Coarse particle content
  3.4 Soundness
  3.5 Mechanical resistance
  3.6 Expansion on setting
Appendices
A DETERMINATION OF CHEMICAL COMPOSITION AND LOSS ON IGNITION
  A.1 Determination of sulphur trioxide and calcium oxide
  A.2 Determination of soluble sodium and magnesium salts
  A.3 Determination of loss on ignition
  A.4 Determination of available lime
B EXAMINATION FOR SOUNDNESS
C METHOD OF DETERMINING TRANSVERSE STRENGTH
  C.1 Apparatus
  C.2 Standard sand
  C.3 Preparation of test specimens
  C.4 Transverse strength test
  C.5 Calculation of results
D DETERMINATION OF MECHANICAL RESISTANCE BY THE DROPPING
  BALL TEST
  D.1 Apparatus
  D.2 Preparation of test specimens
  D.3 Standard consistence
  D.4 Mechanical resistance test procedure
E DETERMINATION OF EXPANSION
  E.1 General
  E.2 Extensometer
  E.3 Zero adjustment
  E.4 Gauging and measurement
F METHOD OF STABILIZING CLASSES A AND B PLASTERS
G DETERMINATION OF FREEDOM FROM COARSE PARTICLES

Applies to common gypsum plasters suitable for use in building operations and in the manufacture of building materials.