At first glance, it would appear that one perspires more in the wetter Steambath as the body is constantly covered perspiration.
It is however, known that the greater the temperature, the more the body has to perspire to maintain a comfortable skin temperature. We also know that dry air can evaporate moisture much faster than moist air. Dry days are obviously better for drying clothes than wet days. So it is very misleading to surmise that steambath causes greater perspiration. The heavy perspiration in the steam bath is just an indication that the moist air is unable to evaporate perspiration fast enough from the skin.
People who have sat in both dry saunas and wet steambaths have noted that in the fairly dry conditions of the sauna, they could be in for even ten minutes, and they noticed their skin would still be dry! Does it mean that they didn’t perspire very much?
Their skin remained dry because the dry air could absorb the moisture just as fast as the body perspired – consequently the skin remains dry. This is typical of the first session into a sauna, when the relative humidity is only about 5 to 10%. It is not until one or two ladles of water are thrown onto the rocks, that the humidity will climb to 10 or 15% and slow down the rate of evaporation. Now the skin glistens with moisture and the beads of perspiration begin to roll.
As the humidity increases further, another phenomenon begins. The bather’s skin temperature will rise to a maximum around 40C and will then remain constant. Part of the moister on the bather’s skin will be a result of the condensation of water from the air onto the skin, similar to a glass of water sweating in a warm room.