Fracture (of which effectively the property of crispness is as a result)
itself represents a very difficult characteristic to measure, due to the fact
that a fracture event never occurs identically a second time. A convenient
physical test is to compress a population of multi-particulate products
constrained within a container such as the Ottawa Cell (see Figure 22 as
previously described). Figure 23 shows a typical graph produced by the
bulk compression of a crispy multi-particulate product using an Ottawa Cell.
In such a test, the multi-peak jagged curves obtained will result from the
fracture of a number of flakes/pieces, each peak corresponding to the
rupture of a single flake/piece. This is different from the situation where a
single piece of sample is being compressed. However, it offers an averaging
effect test of a more representative portion of the sample which is much
more repeatable. The multi peak curves obtained may then be analysed
using special calculations.