Sinking agents are special chemicals that, although applied along the glazing line, show their effect only during the firing phase inside ceramic kilns and act on the material (typically the glaze) located in the layer beneath them.

This action influences the fusibility of the material on which the product has been applied, resulting in the formation of small dips in correspondence with the sinking agent itself. The fusion process is triggered by special fluxes that, thanks to their active inorganic component, act locally and at an earlier stage (at lower temperatures) compared to the general melting of the rest of the material. This difference in timing is crucial for creating three-dimensional effects.