An automated computer-controlled method and apparatus for measuring the
quality or fineness of a pigment dispersion sample, comprising placing
the pigment dispersion at the deep end of the tapered path of a Hegman
gage block, placing the Hegman gage block in a holder in a motorized
drawdown device that draws the scraper along the length of the tapered
path at an angle and to at a contact pressure and at a controlled rate,
thereby creating a tapered film sample of paint whose thickness tapers
from a maximum thickness of 100 micrometers to a minimum thickness of
zero. An illuminator assembly illuminates the sample with a substantially
collimated light source at an intensity level and the light reflected
from the sample is collected by a lens onto a photodetector array in a
digital camera. After a time interval the camera acquires an image of the
sample. The image is digitized and stored in a memory in the computer and
then a portion of the image within a region of interest corresponding to
the sample in the tapered path is analyzed to detect and count pigment
agglomerates that protrude above the surface of the sample.