Answer:
4 layers of material
Step-by-step explanation:
A long time ago the typoe of construction that used tiles, such as moisacs required a lot of concentration and work. One of the most important things was to choose the wall, then cover the wall with resin and after that they had to put 3 layers of plaster all over the wall, finally they used to put pieces of colored glasses ( tiles) and the process was over.