The Global Leader In Viscosity For Over 75 Years
Brookfield AMETEK

Blister Pack

Test Principle

The objective was to evaluate the hardness of blister packs by compression using a hemispherical probe.


The increasing use of blister packs for unit dose packaging of tablets, capsules or lozenges in the pharmaceutical industry demands for good quality packaging. Blister packs should provide some degree of tamper resistance avoiding accidental opening during transportation and by children. A quality blister pack should be consistent in the force required to extract the tablet and easily opened by weaker patients and the elderly. The degree of stiffness of a blister pack will however affect its effectiveness. Measuring the required force to push-through a blister pack is therefore necessary.

The CT3 texture analyser utilises a hemispherical probe that simulates the force applied by the fingers to remove a tablet from a blister pack. Probes complimentary to the size and shape of the blister can also be manufactured to meet customer requirements.



  • CT3 with 10 kg load cell
  • Fixture Base table (TA-BT-KIT)
  • Finger Probe (TA-FP)


  • Test Type: Compression
  • Pre-Test Speed:°.5 mm/s
  • Test Speed: 1.0 mm/s
  • Post-Test Speed: 4.5 mm/s
  • Target Value: 8 mm
  • Trigger Force: 15g

Note: Faster pre-test and post-test speeds may be considered for your application.


  1. Attach the hemispherical probe to the load cell
  2. Place the blister pack accessory on the base table
  3. The accessory has an aperture to accommodate the forced capsule/tablet.
  4. Place and align the packaged capsule on its lidding side with the aperture and its base (cavity or pocket side) centrally under the hemispherical probe
  5. Commence the test

Note: Tablets and lozenges can also be tested but the shape and size of the aperture may need to be considered.

When optimising test settings the hardest sample is best tested first in order to predict the maximum testing range for subsequent samples.


The following is a typical TexturePro CT plot.

Click to enlarge

The above graph shows the force required to extract a hard capsule from a blister pack.


When a trigger force of 15 g has been attained at the sample surface, the probe proceeds to exert a force on the blister pack to a distance of 8 mm during which time the capsule is pushed out of the pack. The maximum force to expel the capsule is indicated by a peak on the graph. This is a measure of “hardness 1”. The area under the curve is automatically calculated as the “Work Done Hardness 1.” The higher the force to expel the capsule from the blister pack, the harder the packaging material.

Click to enlarge

The graph in Figure 2 shows the load verses distance for the force required to extract a hard capsule from a blister pack

Tests obtained to extract 6 capsules from a blister pack give the following mean Hardness and Hardness Work Done values below:

Click to enlarge