Is there a way to make an ink that appears from the heat or moisture of a persons hand?
Lemon juice or even milk can be used as ink. When heated by an
iron or light bulb, the ink will turn brown. It doesn't necessarily
disappear when cooled off again. There are other chemical inks that
will fade out with the cooling off, but I don't know their
availability to the commercial market.
Sensible heat is the heat required to raise the temperature of a substance. When determining the heat of a vapor, moisture must be considered as it removes heat from the vapor (in order to heat the moisture [water vapor] to the ambient temperature). Dry steam has no moisture. Dry air has no moisture (a physical improbability). Air normally has moisture determined as relative humidity. This humidity [water vapor] must be heated with the air. Then…
Within the pot handle (solid) heat transfer is by conduction. Within a persons hand heat is transferred namely by conduction. Heat convection does occur by motion of the body fluids but it's slower. When you grab the hot handle of a pot you can immediately feel the sensation of "hot".Heat conduction is the mechanism responsible for this fast transfer.
this is simple as it see look when a body sweat there is moisture on surface of skin and when this moisture evaporate then ther eis transfer of heat from high temperature to low temperature that's why we feel cool after sweating ..... It needs heat to convert moisture to a vapour and this heat is supplied by the body via the skin. The loss of heat is felt as cooling.