This part of ISO 8130 specifies a method for determining the now properties of a mixture of coating
powder and air. The method reflects commercial
practice in powder spraying (see "Bibliography",
annex B).
The results obtained are influenced by the composition of the coating powder, its density, particle size
distribution and particle shape, together with the
tendency of the particles to agglomerate and to accept a triboelectric charge.
NOTE 1 It is well known that the transport and spraying
characteristics of powders are highly dependent on their
flow properties in bulk and In air. The procedure described
in this method is considered to be more meaningful than
the "flow angle" approach sometimer used to evaluate
bulk flow properties . In the latter, the angle of the cone
formed when a powder is allowed to flow through a vertical funnel on to a horizontal surface is measured . A given
mass of powder with good flow properties forms a
shallower cone than an equal mass of a powder with
poorer flow . The objections to the flow angle method are
that it is difficult to obtain a precise measurement and that
the powder is used alone, whereas during application it is
mixed with air