A new formulation of the protective coating for historical monuments Rachid Benkmil, Lahcen Bahi, Ahmed Akhssas, Latifa Ouadif, Driss Elhachmi and Toufiq Ait El fakih E3S Web Conf., 150 (2020) 03020 Published online: 12 February 2020 DOI: 10.1051/e3sconf/202015003020