Answer

In regards to the wetness on the forehead, as for the first sajda, the skin will touch the soil on the turba (sajda). If the turba is new, when you touch the turba, some of the soil may come on to your forehead. If the soil that comes to your forehead, fully covers it, because as you know during sujud not all your forehead has to touch the sajda. As long as parts of your forehead touch the sajda then that’s ok. However, in the case that the full part of the forehead that touches the sajda is fully covered with soil then you have to remove that soil, or part of the soil, in order to have your skin touch the turbah, in order for it to be counted as a sajda, otherwise it won’t be counted as a sajdah. Usually this is a very rare case, however if it happens, this is what you will have to do.

Sheikh says that if you prostrate on the turbah and the turbah from the wetness turns into clay you cannot prostrate on clay which he says doesn’t usually happen. If it does happen, and it turns it into clay then you have to prostrate on the particles of the sajda, not the actual clay, but the sand or soil that is present on the sajda. But not on the clay, clay you cannot prostrate on. As for the water, usually when you apply pressure from your forehead on the turbah usually the water move to the side of the turbah due to the pressure applied. And the other case of soil turning into clay, it is a very rare case.