experimenting with clay plaster

I mixed up a batch of homemade clay plaster using approximately 1 part clay (from a ceramics store) to 2.5 parts sand (play sand from a hardware store), plus straw (from a pet store, but chopped up into smaller pieces using an old kitchen blender). 

I used the same mixture for both the plaster on the walls and for making the mud tiles, at times adding blue pigment to the mix, or using different colored clay to change the colors.

Previous attempts of sticking mud brick tiles directly on the walls using a mud mortar led to the brick tiles falling off soon afterwards (hence, the broken blue tile shown above). This time I cleaned the wall thoroughly and primed it using a coat of casein primer. Casein saturates untreated surfaces, making them more uniform to help the performance of subsequent finishes. 

The first coat I applied using a small putty knife, moving upwards in small strokes, with a slightly wetter mixture.

For the smooth coat, the mixture was a bit drier and I waited until the first coat was completely dry before adding. For better grip, I sprayed the first coat with water before adding the second coat. 

After it was applied, but still wet, I used a trowel to smooth out the second coat.

After the second coat was completely dry, I attached the mud tiles using a mud mortar. (1 part clay to about 2.5 parts sand - no straw this time).

Again, before attaching the tiles to the wall, I sprayed the wall slightly with water.