Front:
OSTCARD
THERMOMETER
90-95
85-90
80-85
75-80
70-75
65-70
60-65
55-60
Back:
DaMert Company-Oakland California
The front of this card has been coated with 8 bands of thermal sensitive LIQUID CRYSTAL, each
formulated to display color in the 5 degree range indicated. When the band color is BROWN, the
temperature is at the low end of its range (for example, 70°-71°), GREEN is mid range (72°-73°).
and BLUE is high range (74°-75°). The color is caused by aligned crystal molecules twisting around
each other scattering different wavelengths of white light back as color. Initial LIQUID CRYSTAL
research was performed in 1888 by Austrian botanist Freidrich Reintzer.
Do not leave in sunlight
For best results use a felt tip pen
STAMP
