Finding Pietra Serena with technique of Stucco Lucido

the guild tried to make something similar to pietra serena (a gray sandstone also known as Macigno stone) by using different material from GRC by applying techniques from Stucco Lucido.  Stucco Lucido is formed from dissolved animal glue, boiled linseed, and dissolved Bologna’s plaster (calcium sulfate). Natural earth shades are added to the mixture until the desired color is reached. The mixture is sieved and left to cool. So the color stays consistent a single mixture for all surfaces treated is made. Coats are applied to the surface and sand of each layer before moving on to the next one. In order to achieve a glossy brushed stucco finish, the process is continued by applying cross-layered coats. The last coat is applied with an iron spatula that is at least 8 cm wide. The mixture being pressed until the desired gloss is achieved. This technique avoids using wax, the glossy effect is achieved with a long hand-processing of the mixture that is laid on the surface and is what creates a fluid and transparent coating.