A have listened to the entire series of Jack Reacher books by Lee Child. I am crazy for Reacher. I admire his minimalist and independent life, and his unflappable personality. His senses of duty and justice are worthy enough to forgive all of the neck bones he has crushed.
(By the way, book Reacher does not bear any resemblance to movie Reacher. And I'm not just talking about physical appearance. Book Reacher has no ego, he doesn't care about praise or credit. Movie Reacher is very self-conscious. Do I look tough enough? Can they tell I'm short? I don't begrudge Lee Child for taking the biggest movie rights deal he could get. He earned it. As for Tom Cruise, buying something is not the same as earning it.)
One of Reacher's quirks is his addiction to coffee. He never turns down a chance to drink coffee. He'll drink any coffee, good or bad, at any time of day, from any cup. But he knows what type of cup he prefers, and notices when he's using one that he likes.
"A bad coffee mug has a thick lip—too wide, too shallow, too much mass—it will cool the drink too fast. A good coffee mug is cylindrical in shape, narrow in relation to its height and with a thin lip."
For years I have only made mugs in one size: enormous. They hold about 20 oz. This is how I drink coffee, one giant cup in the morning. Customers regularly ask me for normal sized mugs, but I have never felt compelled to make them until now. Now I want to make a mug that Reacher would like.
But before I could do that, I had to reconcile my confusion about Reacher's description of an ideal mug. I understand why a wide or shallow mug would allow coffee to cool too fast. But I was surprised at the idea that a thick-walled mug would hasten the cool-down. I always assumed a thicker-walled ceramic vessel would be a better insulator, not worse. Then I started to think about it in terms of refractories, which are all of the dense objects that are inside a kiln when firing. Refractories mostly refer to kiln shelves and posts, but the pots themselves are refractories too. We potters know that the more refractories we have in a kiln, the more energy it takes to fire, because refractories absorb a lot of energy before they can act as insulators and radiators of energy.
Does a thick-walled mug absorb heat like a refractory? I decided to find out for sure, in a situation that simulates coffee drinking, not kiln firing. I made two nearly identical vessels. One with a thin 1/8 inch wall, and one with a thicker 1/4 inch wall. I filled them with equal amounts of boiling water, then started taking the water's temperature. I measured the temperature at one minute intervals, for ten minutes.
I ran this test four times. I made sure to return the cups to room temperature in between, by running them under cool water. The results had some small variations but were overall consistent. In the first two minutes of the test, the thick cup lost 3 or 4 more degrees than the thin cup. After two minutes (I'm guessing this is when both cups were sufficiently heated through) both cups lost heat at the same rate per minute. The difference is small, but technically Reacher is right.
"No doubt about that," Reacher would say. To himself inside his head.
Cylindrical in shape, narrow in relation to its height and with a thin lip. Glazed in a no-fuss colorblock of gray and off-white. Holds 10 to 12 oz. Positioned next to my "Enormous Coffee Mug" the official name on the hang tag will be "Normal-Sized Mug," with the subtitle "aka Jack Reacher's ideal coffee mug." These will be available for sale for the first time at my Open Studio, coming up on December 10-11.
And no, I am not admitting that I drink too much coffee. I am only admitting that some people prefer to drink coffee in smaller quantities throughout the day.