As it happens, my town was located several hundred miles north of the swath that the Great Eclipse of 2017 cut across the United States. This meant that, while the sky turned gunmetal, the temperature didn’t drop and clouds obscured any part of the event that might have been visible from my home.

All was not lost, however. NASA live-broadcast the eclipse as it made its way across the country and I was prepared to participate in it vicariously. I purchased a “Total Eclipse of the Sun” Forever stamp from the United States Postal Service. This is the first USPS offering to feature thermochromic ink. Normally the stamp’s face is dominated by a black disc, which is how the moon appeared today when it blocked the sun. That’s what you see above.

Pressing one’s thumb on the image for a few moments heats it to the point that the cratered face of the moon appears.

Before long the ink cools and the black disc reappears. I liked the concept, and hope the USPS fields many stamps in the future that make use of thermochronic ink!