  A description is given of the traveling solvent technique, which has been
used for the crystal growth of both congruently and incongruently melting
materials of many classes of intermetallic, chalcogenide, semiconductor and
oxide materials. The use of a solvent, growth at lower temperatures and the
zoning process, that are inherent ingredients of the method, can help to grow
large, high structural quality, high purity crystals. In order to optimize this
process, careful control of the various growth variables is imperative;
however, this can be difficult to achieve due to the large number of
independent experimental parameters that can be grouped under the broad
headings growth conditions, characteristics of the material being grown, and
experimental configuration, setup and design.This review attempts to describe
the principles behind the traveling solvent technique and the various
experimental variables. Guidelines are detailed to provide the information
necessary to allow closer control of the crystal growth process through a
systematic approach. Comparison is made between the traveling solvent technique
and other crystal growth methods, in particular the more conventional
stationary flux method. The use of optical heating is described in detail and
successful traveling solvent growth by optical heating is reported for the
first time for crystals of $Tl_5Te_3$, $Cd_3As_2$, and $FeSc_2S_4$ (using Te,
Cd and FeS fluxes, respectively).
