Anyone who has worked with powders will know how easily they change their density, just as a result of handling them. Tip them from a beaker and they aerate, or tap the beaker on the bench and observe a reduction in volume as the powder becomes compacted.
These changes in density are a consequence of changes in the stress applied to the powder. As discussed previously, variation in stress level is likely to have a major impact on how the powder behaves, within a process or application, but also during a measurement. It is therefore essential to ensure the powder is prepared for any test by first establishing a uniform stress in the powder bed and eliminating pockets of air or localised compaction.
This preparation step is called
A conditioning cycle is usually completed prior to every test in order to remove the variability introduced by the operator during loading of the sample, and any residual compaction from previous tests. The exception is where an intentionally consolidated sample is being evaluated, in which case conditioning is not employed.