A new procedure to detect urea–formaldehyde adhesive in industrial particle board is presented. The method uses thin sections stained with a visible dye (gentian violet) and a fluorescent dye (brilliant sulphaflavine), respectively, in a two-step procedure. Microscope images of a selected area of interest acquired in visible and fluorescence modes are combined to obtain sufficient contrast, enabling semi-automated detection of adhesive by means of image analysis. No addition of dye prior to particle board production is necessary.