HI!
This weekend I was talking to an architect friend who mentioned two more ways to waterproof earth plasters:
1) Potassium Silicate ("dissolvable glass") ; it goes on in 2 coats, first 1:1 with water, and 2nd pure silicate. If you want to do it with color use white paint as a base: 5kg of Zinc Oxide and 4 lt. (5kg) potassium silicate--mix the paint a day before using. You can add any natural pigments you like, or colored earth. leave 12 hours drying time between coats, and don´t do it in rain, freezing weather or strong sun.
2) an old monk´s recipe: pigments mixed with beaten eggs.
Does anyone have any experience or comments on either of these techniques?
RIKKI