History:
Buckminster Fuller, a scientist from UK was a remarkable inventor, architect and a designer. He was responsible for the Geodesic dome among other designs but the most fulfilling design was the bathing unit, called Dymaxion that was a very unique concept. This design came from his observations while in the navy that exposing soiled articles to the open deck, removed oils and other greasy material. He attributed this action to the presence of wind and fog.
Based upon this hypothesis, he designed a bath that would use the cleansing property of water and solvents but in a fog machine that would produce very small droplets of water and solvents – the “fog gun”. This would enable the cleansing of the skin and surfaces without the damaging effects of large amounts of water applied at high pressure on the skin surface in a traditional shower.
This fog gun was sometimes combined with a hot infrared lamp and some solvents and evaluated by the University of Chicago in 1948. The system was so efficient that it used only about 1 liter of water per hour.
Science:
Formation of fog: Water has a very high surface tension which means that water tends to form a “skin” on the surface of water. This typically leads to the formation of droplets when water is sprayed. Thus the formation of fog does not require much modifications or addition of solvents or surfactants. Water will form minor droplets and they will generally tend to remain as stable droplets. Thus the first part of fog gun requires no additional energy but the ability to spray at a high pressure.
What happens when we take a bath?
There are two components that require cleaning on a human body or skin.
- 1.Water soluble component: This is sweat, salt and other water soluble components. These components only require an exposure to water and this takes away the salts as a solution in the water. No detergent is required. Typically, a wet towel would also serve this purpose. It will dissolve the water soluble component.
- 2.Water insoluble component: The skin typically secretes oils, skin particles, proteins and other components that are not miscible with water. Exposure to pure water has no effect on these components and taking a shower will have no effect on removing these oils. However, to remove these water immiscible components requires use of a “linker” chemical molecule that one side binds to the oil and on the other side binds within water. This linker then serves as a bridge that makes the oil “soluble” in water and thus enables removal of oil and other water insoluble dirt. This linker is the commonly used soap. Detergents also serve the same purpose.
The last component is mechanical scrubbing such that some amount of pressure that will enable the dissolution of both components (water soluble salts and water insoluble oils) very easily. Similarly, at bathing temperature of water enables the cleansing reaction to be more efficient.
Why does it work?
The short answer is that these water droplets form a large surface area that can hold on to a large amount of oil in the presence of minuscule amounts of soap or detergent.
This is how it works in detail.
A component of a good bath are the following items shown in icons. Water is always nicer if it is warm and there is significant energy costs associated with heating water since water has a remarkably high heating capacity. It has among the highest heat capacities of all the common materials known to man. Soap is an additional component and often due to our usage with large amounts of water that can also pull out some essential oils, the detergents are formulated sometimes to replace the oils present on the skin with scents, fragrances or delicate creams.
A conventional bath employs soap and water. A considerable amount of the water is wasted since it is not useful for the cleaning purpose and is mostly flushed down the drain. The heating costs associated with that water is similarly wasted.
In contrast a fog gun bath is energy and water efficient. Chemically, the water droplets are more effective in cleaning and can pull out more dirt and salt. Since lesser water is used it also saves considerable amount of heating costs.
This is a simplistic representation since bathing soaps and detergents are formulated to form the right amount of micelles without causing skin damage. The fog gun baths will need to be designed with all the modern technology that we have available such as sonication technology for vaporizing droplets, use the least amount of polluting and phosphate containing detergents such that the bathing action happens quickly with the least amount of water and soap wastage.