The process of silk weighting with methacrylamide (MAA) initiated by ammonium persulfate was studied to optimize the operating conditions to obtain high yields of grafted monomer. The influence of MAA concentration, liquor ratio, concentration of initiator, contact and heating time, acidification, and swelling agents were considered, and optimum operating conditions were outlined. Moreover, various monomethacrylates and dimethacrylates were grafted onto silk as alternative to methacrylamide. Most of these showed graft yields higher than MAA in the same operating conditions and some were found suitable for silk weighting since the weighted fibers show soft hand and good dyeing behavior. DSC and TGA analyses of grafted silk enabled to evaluate the influence of various monomers on the thermal behavior of the weighted fibers. Moreover, on the basis of DSC data, a correlation between the calculated enthalpy of grafted polyMAA and monomer content was studied. The molecular structure of silk grafted with methacrylic monomers was finally characterized by FTIR analysis. (c) 2006 Wiley Periodicals, Inc.