Hindered Settling - When a controlled rising current of water is introduced across the area of the bottom of a classifying vessel, a sand can be expanded into a state of teeter. In this teetered state the sand grains will classify themselves so that the coarse grains report to the bottom of the column where they will stay relatively close to each other with high velocities of water flowing between them, whilst the finer particles will be dispersed to the higher levels of the column where they will stay in more open suspension.

This teetered suspension is, to all intent and purposes, a dense media and may be used to float off another material, such as coal or lignite, that is light enough to be supported by the suspension irrespective of their particle size. Equally, a concentration of heavy minerals may be made, as hindered settling has the effect of enhancing the difference in specific gravities between minerals, to the extent that a heavy mineral can generate sufficient density to support quartz.