Este fenómeno denominado «plaquing» ocurre por reacciones no uniformes de desprendimiento de gases durante la cocción de la arcilla que tiene relación con los cambios bruscos de temperatura. Estos vapores o gases forman una burbuja plana en la cara de las piezas que está en contacto con el azulejo.
To avoid its formation you can take the following precautions:
1) Condition the clay slab well, spread it on the tile avoiding encapsulating the air.
2) Slide a rolling pin over the dough before cutting.
3) Preheat the oven
4) When placing the pieces in the oven, protect them with an aluminum tray to distribute the heat indirectly.
5) Bake twice: once for the time recommended by the manufacturer, cool and return to the oven for an additional 10 minutes.
While these recommendations will help reduce air plates, they will not completely eliminate them. To remove them from your pieces, use different grades of sandpaper and acetone soaked in a microfiber cloth.
You can also work the back of your pieces with different textures that will help to obtain a more professional finish.