Polycondensation of nylon-6,6 onto Kevlar and glass fibers has been previously proposed by our group as a surface treatment for composite fabrication. The present article reports the optimisation of this procedure for glass fibers via a study of the first two steps of the polymerisation, the esterification of pendant OH groups at the glass fiber surface by adipoyl chloride, and the amidation reaction occurring between the grafted acid chloride moiety and diamino-1,6-hexane. X-ray photoelectron spectroscopy (XPS) and potentiometric results show that esterification proceeds within the first 30 min of the reaction. The amidation reaction was characterised by Kjeldahl and XPS procedures and was found to be complete after less than one minute. Results also underline the importance of pH control during the reaction to limit hydrolysis of the ester bond at the fiber surface. Thermogravimetric analysis of samples obtained by a manual procedure as well as by an automated lab-scale reactor show that the amount of grafted material increases linearly with number of passes, indicating the occurrence of a negligible amount of termination reactions up to 60 passes.