  Understanding planet formation requires to discern how dust grows in
protoplanetary disks. An important parameter to measure in disks is the maximum
dust grain size present. This is usually estimated through measurements of the
dust opacity at different millimeter wavelengths assuming optically thin
emission and dust opacity dominated by absorption. However, ALMA observations
have shown that these assumptions might not be correct in the case of
protoplanetary disks, leading to overestimation of particle sizes and to
underestimation of the disk's mass. Here, we present an analysis of high
quality ALMA and VLA images of the HL Tau protoplanetary disk, covering a wide
range of wavelengths, from 0.8 mm to 1 cm, and with a physical resolution of
$\sim$7.35 au. We describe a procedure to analyze a set of millimeter images
without any assumption about the optical depth of the emission, and including
the effects of absorption and scattering in the dust opacity. This procedure
allows us to obtain the dust temperature, the dust surface density and the
maximum particle size at each radius. In the HL Tau disk, we found that
particles have already grown up to a few millimeters in size. We detect
differences in the dust properties between dark and bright rings, with dark
rings containing low dust density and small dust particles. Different features
in the HL Tau disk seem to have different origins. Planet-disk interactions can
explain substructure at the external half of the disk, but the internal rings
seem to be associated to the presence of snow lines of several molecules.
