Sweating Polypores

These red-banded Polypores are very common in our forests and are found on dead and dying trees, in this case on a stump. Often when we find them they are "sweating" and I have never been able to find an explanation of this phenomenon. The weather does not seem to have anything to do with it, or the humidity and I have no idea what the cause might be, nor do I know if the liquid is water or something else, not having dared to taste it. These were photographed in Wallace Falls State Park last autumn.