We report the first clear experimental demonstration of large amplification of smallscale spatial perturbations by stimulated thermal Rayleigh scattering (STRS) of a CW laser beam propagating through an absorbing medium in a context normally associated with thermal blooming. A single-mode argon-ion laser beam with = 488 nm was propagated vertically downward through a 1 .2 m cell filled with CC14 that was doped with an absorber to have optical depths in the range 0.5-2.3 . A shear-plate interlerometer near the cell input generated the perturbation. Fringe growth was rapid and visually obvious, as was competing growth from dust specks, etc. The measured growth rate is in good agreement with the asymptotic rate from analytic STRS theory.