We had a brown wall, consisting of some loam- or clay-like material. (When you touch it, it smells like in the pottery workshop.) We want to paint it white.
We cleaned the wall and brushed it thoroughly, and applied white lime paint to it. However, the paint started to mix with the brown underneath, leading to a... very unsatisfying result:
We're done for the day, and are planning to wait until the wall has thoroughly dried, and try again with more lime paint. We are prepared to apply as many layers of lime paint as possible, but we're not sure whether the result is ever going to be fully white.
We did think about using conventional wall paint from now on, but we fear it would not fare much better on the loamy surface, and break away.
Does anyone have an idea how to best proceed from here?
Also, what could the brown wall have consisted of? Are there common techniques that make a wall smell like clay?