A method for assessing the cure status of a fibrous blanket manufactured with mineral fibers and binder is disclosed and comprises a using an online optical reflectance measurement as an assessment of cure status. The optical reflectance measurement may preferably be a color image taken of any surface, and in particular of a sectioned face, after which the image is optionally divided into multiple regions of interest (ROI) and analyzed for a color system variable that is representative of cure status. In some embodiments, the color system variable is the B value. Alternatively, the optical reflectance measurement may be UV or IR reflectance of a sectioned face. When two or more regions of interest are defined on a sectioned face, comparative information is valuable to assess cure at different levels, layers or portions of the interior of the fibrous product.