The synthesis of phenol-formaldehyde resol resins was carried out in two stages to facilitate the start of a conventional batch process. In the first stage, the starting material solution was preprocessed in a continuous-flow stirred-tank reactor with a 5-min residence time. In the second stage, synthesis was continued in a batch reactor. Samples were analyzed by titrimetric methods, gas chromatography, nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. Most of the starting materials were consumed in the preprocessing reactor, which allowed better control of the reactivity of the prepolymer solution in the second stage. The methylolation and condensation reactions proceeded steadily during the production process in the batch reactor. The results of the study indicated that dividing a conventional one-stage batch process into two stages could facilitate the control of the initial stages of resol production. (C) 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 371-379, 2007