A method for visualizing biofilm on a solid surface. The method comprises steps of:(a) providing a solid surface which has been in contact with an aqueous medium and at least a portion of the solid surface potentially is covered with biofilm,(b) maintaining the solid surface in a horizontal position and covering the solid surface with an aqueous dispersion of carbon particles,(c) tilting the solid surface at an angle of at least 5° from horizontal to allow excess aqueous dispersion of carbon particles to flow from the surface,(d) detecting any biofilm present on the solid surface by determining whether there are areas not covered by aqueous dispersion of carbon particles.
