Tablet hardness testing

Tablet hardness testing, is a laboratory technique used by the pharmaceutical industry to test the breaking point and structural integrity of a tablet "under conditions of storage, transportation, and handling before usage"[1] The breaking point of a tablet is based on its shape.[2] It is similar to friability testing,[1] but they are not the same thing.

Tablet hardness testers first appeared in the 1930s.[3] In the 1950s, the Strong-Cobb tester was introduced. It was patented by Robert Albrecht on July 21, 1953.[4] and used an air pump. The tablet breaking force was based on arbitrary units referred to as Strong-Cobbs.[3] The new one gave readings that were inconsistent to those given by the older testers.[3] Later, electro-mechanical testing machines were introduced. They often include mechanisms like motor drives, and the ability to send measurements to a computer or printer.[3]

There are 2 main processes to test tablet hardness: compression testing and 3 point bend testing. For compression testing, the analyst generally aligns the tablet in a repeatable way,[2] and the tablet is squeezed by 2 jaws. The first machines continually applied force with a spring and screw thread until the tablet started to break.[3] When the tablet fractured, the hardness was read with a sliding scale.[3]

List of common hardness testers

There are several devices used to perform this task:

Units of measurement

The units of measurement of tablet hardness mostly follows standards used in materials testing – the International System of Units.


  1. 1 2 3 Joseph Price Remington (2006). Remington: The Science And Practice Of Pharmacy. Lippincott Williams & Wilkins. ISBN 0781746736.
  2. 1 2 "Tablet hardness testing". Sotax. Retrieved 16 February 2013.
  3. 1 2 3 4 5 6 "Some Information on Tablet Hardness Testing". Engineering Systems. Retrieved 16 February 2013.
  4. 1 2 3 Robert Albrecht (Jul 21, 1953). "Tablet Hardness Testing Machine". United States Patent Office. Retrieved 16 February 2013. US 2645936
  5. 1 2 3 4 5 "Quality control of solid dosage form". Scribd. Retrieved 16 February 2013.
  6. 1 2 McCallum, A., Buchter, J. and Albrecht, R. (1955). "Comparison and correlation of the Strong Cobb and the Monsanto tablet hardness testers". Journal of the American Pharmaceutical Association. 44 (2): 83–85. doi:10.1002/jps.3030440208. PMID 14353719.
  7. Russ Rowlett (September 1, 2004). "How Many? A Dictionary of Units of Measurement". University of North Carolina. Retrieved 16 February 2013.

Further reading

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