Monday Morning Brief | Putting thermochromic ink to the test

Aug 28, 2017, 4 AM

How resilient is the heat-sensitive ink on the United States Total Solar Eclipse stamp? To find out, Linn’s Stamp News conducted a four-week test. Linn’s managing editor Chad Snee discusses the results.

Full Video Transcript:

Greetings fellow stamp-hobby enthusiasts and friends! Welcome to the Monday Morning Brief for August 28, 2017.

Did you have a chance to see the total solar eclipse that swept across the United States a week ago? Where I live — Troy, Ohio — we had coverage of 88 percent, and the patchy clouds parted just long enough to get a clear view.

Just about two months prior to this captivating astronomical meeting between our nearest star and Earth’s moon, the United States Postal Service issued its Total Solar Eclipse forever stamp.

In the weeks leading up to the Aug. 21 eclipse, news outlets across the country and around the world trumpeted the new stamp and its innovative feature — thermochromic ink.

This heat-sensitive compound appears black at room temperature. When warmed, as from the touch of a fingertip, the ink becomes clear, revealing an image of the moon on the stamp.

To protect the properties of the thermochromic ink, the Postal Service sold what it calls a “protective sleeve,” a black envelope sized to hold a 16-stamp pane of Total Solar Eclipse stamps. Printed on the back of the envelope is this rather cryptic statement: “This sleeve is for stamp preservation only.”

All of which prompted us to ask some questions: How resilient is the thermochromic ink? Would exposure to excessive heat and light adversely affect the ink’s properties?

To find out, we put three Total Solar Eclipse stamps through a four-week test.

The first stamp served as the control — it was kept at room temperature in complete darkness. The second and third stamps were affixed to separate white index cards.

The card bearing the second stamp was affixed just below a fluorescent desk lamp that remained on 24 hours a day, thus providing near constant conditions of light and elevated temperature.

The card carrying the third stamp was placed on the dashboard of a car during the day and removed when the car was in transit or garaged for the night. This provided variable conditions of light and temperature.

Here are the three stamps after the test, as seen at a room temperature of about 72 degrees Fahrenheit.

The thermochromic ink on the first stamp is completely black; the moon is not visible at all. On the second and third stamps, in contrast, the moon is visible — more so on the third stamp than on the second.

Next, the three stamps were warmed briefly using a hot plate and then photographed. The stamp kept in the dark now shows the normal image of the moon, indicating no apparent negative affect on the thermochromic ink.

Almost complete degradation of the ink is seen on the second and third stamps — the moon on each shows only a slight change in color.

The takeaway from these results is straightforward: House your Total Solar Eclipse stamps in an album stored in a cool, dark place. Come to think of it, that’s good advice for all of our philatelic treasures.

For Linn’s Stamp News and the Scott catalogs, I’m Chad Snee. Have a great week enjoying our wonderful hobby. Cheers!