The invention relates to polymer paint and varnish industry and can be used in production of coatings for various constructions to protect the constructions (for example, ships, cargo tanks, tanks of railway and road vehicles, etc.) from aggressive environment or damage caused by storage of chemicals.A method for excitation of polymerization in novolacs is provided. Said method comprises the following steps: mixing of novolac monomer solution with cationic photoinitiator of concentration from 0.5 to 5 % and treating said solution with an ultraviolet light source for 3 to 10 minutes with source power from 0.5 to 1.5 kW. A cross-linked novolac of thickness equal to or less than 0.5 mm is thereby obtained.