An assembling method for mosaics of tesserae made of transparent glass comprises the phase of gluing a plurality of tesserae on a substratum comprising a transparent cloth to form a mosaic portion suitable for being subsequently glued or fixed to a wall, a floor, or other structures. The substratum comprises a cloth made of fiber glass preferably a cloth comprising 100% of fiber glass. The cloth made of fiber glass is formed with a warp comprising a number of yarns between 215 and 225 yarns/dm. The cloth made of fiber glass is formed with a weft comprising a number of yarns between 215 and 225 yarns/dm.