Changeable Ink Can Make Moon Appear on U.S. Eclipse Stamp

The U.S. Postal Service will issue on June 20 a forever stamp noting this year’s total solar eclipse using a special kind of ink that will make an image of the moon appear beneath your thumb.

The stamp, printed in panes of 16, will be released in anticipation of the August 21 total eclipse of the sun that will track diagonally across the United States from Oregon to South Carolina, the Postal Service said today in a news release. It’s the first such eclipse appearing over the United States mainland since 1979.

Thermochromic ink is being used on a U.S. stamp for the first time, the Postal Service said in a news release. As sold, an image of the eclipse appears in the center of the stamp. Using the body heat of your thumb or fingers and rubbing the eclipse image will reveal an underlying image of the moon. The image reverts back to the eclipse once it cools.

Thermochromic inks are vulnerable to UV light and should be kept out of direct sunlight as much as possible to preserve this special effect. To help ensure longevity, the Postal Service will be offering a special envelope to hold and protect the stamp pane for a nominal fee.

The stamp images are photographs taken by astrophysicist Fred Espenak, who is known as Mr. Eclipse, of Portal, Arizona. The photo of total eclipsed moon on the stamp was taken March 29, 2006 in Jalu, Libya.

Tens of millions of people in the United States hope to view the rare event. The eclipse will travel a narrow path across the entire country for the first time since 1918. The path will run west to east from Oregon to South Carolina and will include portions of 14 states.

The first-day-of-issue ceremony will be at 1:30 p.m. (Mountain Time) June 20 at the Art Museum of the University of Wyoming in Laramie. The university is celebrating the summer solstice on that day. Prior to the event, visitors are encouraged to arrive at 11:30 a.m. to witness a unique architectural feature where a single beam of sunlight shines on a silver dollar embedded in the floor, which occurs at noon on the summer solstice in the UW Art Museum’s Rotunda Gallery.

The back of the stamp pane provides a map of the August 21 eclipse path and times it may appear in some locations.

A total eclipse of the Sun occurs when the Moon completely blocks the visible solar disk from view, casting a shadow on Earth. The 70-mile-wide shadow path of the eclipse, known as the “path of totality,” will traverse the country diagonally, appearing first in Oregon (mid-morning local time) and exiting some 2,500 miles east and 90 minutes later off the coast of South Carolina (mid-afternoon local time).

A total solar eclipse provides us with the only chance to see the Sun’s corona — its extended outer atmosphere — without specialized instruments. During the total phase of an eclipse the corona appears as a gossamer white halo around the black disk of the Moon, resembling the petals of a flower reaching out into space.

Art director Antonio Alcalá of Alexandria, VA, designed the stamp.

The Total Eclipse of the Sun stamp is being issued as a forever stamp (currently 49 cents), which is always equal in value to the current First-Class Mail 1-ounce price.

* story updated April 28 to update stamp production details.