A method for the fabrication of a steel product is provided. The method includes the steps of characterizing a layer of oxides present on a running steel substrate which includes providing a portion of the steel substrate comprising a layer of oxides and the portion defines an oxide surface, collecting light (Lr) from the oxide surface using a hyperspectral camera (20) in order to obtain intensity values (Iλ,M) respectively representative of an intensity of a part (Lrλ,M) of the collected light, each part being respectively collected from one of a plurality of points (M) located on the oxide surface and respectively has a wavelength (λ) from a plurality of wavelengths, comparing the obtained intensity values with reference intensity values obtained for reference oxides, and calculating amounts of reference oxides in the layer. A device for characterizing a layer of oxides present on a steel substrate is also provided.