text: Tablets can be made in virtually any shape, although the requirements of patients and tableting machines mean that most are round, oval, or capsule-shaped. More unusual shapes have been manufactured, but patients find these harder to swallow, and they are more vulnerable to chipping or manufacturing problems.
  Tablet diameter and shape are determined by the machine tooling used to produce them; a die plus an upper and a lower punch are required. This is called a station of tooling. The amount of tablet material and the placement of the punches in relation to one another during compression determine the thickness. Once this is done, we can measure the corresponding pressure applied during compression. The shorter the distance between the punches, the greater the pressure applied during compression, and sometimes the harder the tablet. Tablets need to be hard enough that they do not break up in the bottle, yet friable enough that they disintegrate in the gastric tract.
  Tablets need to be strong enough to resist the stresses of packaging, shipping, and handling by the pharmacist and patient.  The mechanical strength of tablets is assessed using a combination of simple failure and erosion tests, and more sophisticated engineering tests. The simpler tests are often used for quality control purposes, whereas the more complex tests are used during the design of the formulation and manufacturing process in the research and development phase.  Standards for tablet properties are published in the various international pharmacopeias (USP/NF, EP, JP, etc.).  The hardness of tablets is the principal measure of mechanical strength.  Hardness is tested using a tablet hardness tester.  The units for hardness have evolved since the 1930s but are commonly measured in kilograms per square centimetre. Models of testers include the Monsanto (or Stokes) Hardness Tester from 1930, the Pfizer Hardness Tester from 1950, the Strong Cob Hardness Tester and the Heberlain (or Schleeniger) Hardness Tester.
  Lubricants prevent ingredients from clumping together and from sticking to the tablet punches or capsule filling machine. Lubricants also ensure that tablet formation and ejection can occur with low friction between the solid and die wall, as well as between granules, which helps in uniform filling of the die.
  Common minerals like talc or silica, and fats, e.g. vegetable stearin, magnesium stearate or stearic acid are the most frequently used lubricants in tablets or hard gelatin capsules.