The Postal Service™ is revising the descriptive stamp text from the article entitled “Stamp Announcement 17-27: Total Eclipse of the Sun Stamp,” in Postal Bulletin 22467, (5-11-17, pages 48-49).
The updated text is shown here:
The heat of your touch is usually enough to activate the thermochromic ink, but other factors could influence this effect, such as lower body temperature, cooler extremities, or cooler room temperatures:
n Body temperature. Since body temperature differs from person to person, you may have to use an additional source of heat, such as a lamp, to reveal the image. When the temperature of the paper cools, the image will revert to the black disc.
n Room temperature. In an overly warm room, you may need to cool the stamps by placing them in an area which is substantially cooler than the room temperature.
Thermochromic inks are vulnerable to UV light and you must keep them out of direct sunlight for extended periods of time. Excessive exposure to UV light could affect the changeability of the ink, which would result in a permanent clearing of the ink to reveal the moon.
— Stamp Services,
Marketing, 7-20-17
