There exist many materials that change color depending on temperature.

Utilizing this phenomena, we could create tattoos that are only visible at certain times. Normally, these tattoo pigments are skin-colored, specially chosen to match your natural tone in that body area, or are transparent. But when exposed to heat or cold, such as if you stepped out into the winter wind, or into the sun, they change to a different color, revealing the tattoo. When you got back to a more normal temperature, they would disappear.

You could even overlay 2 different tattoos, one visible in heat, the other visible in cold.

This could also have medical applications, creating a body temperature tattoo readout, so you would know if you had a fever.
-- DesertFox, Mar 05 2006

Seems like tying or adhering a standard flexible strip thermometer to the area of the body that you desire to monitor would be convenient, practical, and a whole lot easier to remove than a permanent tattoo when you tired of the look, or just decided it wasn't wise to display your emotions so openly on your sleeve. Perhaps designing removable adhesive flexible strip thermometers into cooler tattoo-like designs would have a broader market.
-- jurist, Mar 05 2006


pretty good idea. How about maori tattoos on your face that show up when a lot of blood goes to your face when you are really angry. You get a big bun.
-- zeno, Mar 07 2006


sp. phenomenon.

You could have one of a person who is wrapped in a blanket when it's cold... You might get sick of people rubbing your tattoo all the time.
-- spidermother, Mar 07 2006


My lips turn blue when I'm cold. Does that count?
-- DrCurry, Mar 07 2006



random, halfbakery