I suppose it depends on the material really. For instance, Volcanic ash, such as what we have laying all over the place around here from the Mount Saint Helens eruption in 1980 is really gritty, almost like sand. Wood ash, is much more powdery. I suppose we'll need clarfication as to the exact source of the ash, as well as temperature of conversion to ash, moisture content of the pre ash material, atmospheric moisture content on that day, barometric pressure, etc. to really make a sound determination.