A method of radiative heating for frescoed surfaces has recently been proposed to prevent deterioration caused by moisture condensation. A previous study has stressed the importance of the surface absorptivities, in respect both to the power required and temperature disuniformity. In the present research, these absorptivities are measured for wall surfaces, composed and painted with different colors, precisely with the same techniques used at the time of the original construction (XIV-XVI century), and heated by radiating sources with continuous nearly grey spectra and grey-body temperatures between around 3,200 K and 700 K. For temperatures high enough to permit the realization of compact radiating sources (T <= 1,300 K), the absorptivities result all sufficiently high, thus not requiring high radiating power, and sufficiently close not to create dangerous internal stresses.