The evolution of phenolic resol resin catalysed by barium hydroxide under controlled temperature, formaldehyde to phenol ratio and water dilutability was quantitatively followed by liquid chromatography. Disappearance of phenol and formaldehyde and formation of addition products were quantitatively followed during synthesis. Higher molecular species formed by condensation reactions were diaryl compounds bonded by methylene bridges via para,para and ortho,para positions. No ortho, ortho bonds were detected by C-13 n.m.r. spectroscopy. Gas chromatography was used to follow the evolution of the final resin stored at three temperatures. Temperatures below zero are advisable for storing purposes of these phenolic resol resins.