Clay bricks should NOT be sealed. In an area with freeze thaw, water gets behind the sealer and can pop off the face of the brick. It needs to “breathe” to allow water to migrate in and out of it.
Any water-repellent process blocks this "breathing" property and can cause crystallization inside the brick and exfoliation.
Fornace S.Anselmo accepts no liability for any damage caused by the application of water-repellent substances.
The porosity of clay bricks is natural and it's one of its advantages: it colours fast and will not fade over time.