AbstractThe preparation of an industrially used sequential formulation of a melamine–urea–formaldehyde resin was followed with Fourier transform infrared (FTIR). The analysis allowed us to identify the increases and decreases of the main groups in the resin and to compare this system of resin analysis with results previously obtained by 13C‐NMR analysis. The FTIR analysis, although considerably more limited than 13C‐NMR analysis, allowed us nonetheless to identify and follow the appearance, increase, decrease, and disappearance of several of the main chemical groups during the preparation of the initial urea–formaldehyde (UF) phase of the reaction and the subsequent reaction of melamine with the UF resin that was formed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007