To begin with, you can get a smooth mirror surface on the tile in two ways. The first is to use special additives that are expensive and are most often produced abroad. Second — just add more water to the concrete solution. The strength of the resulting product depends on the method that the manufacturer selects. In order to determine what exactly gives the mirror tile, you need to lightly hit two tiles against each other. If special additives were used in production, the sound will be voiced and clear. If the smoothness of the surface was achieved by a cheap method and to the detriment of strength, that is, with the addition of water — the sound will be deaf. That is, any errors in laying paving slabs will lead to the fact that the coating will quickly collapse.