Tuesday, December 19, 2017


Those of you who have my book, Under the Wild Ginger, may have read my how-to-be-in-the-moment tip number 48, Behold the Cream in Your Coffee.*  It celebrates the simplest of small delights, the way cream billows up from the bottom when poured into a clear glass mug of hot coffee.

Well, as of this morning, I’ve think I’ve reached a new zenith in my ascent of coffee’s small wonders: the layered latte. It’s reported in a Dec. 15, 2017 post on the blog Mental Floss.

While I’ve never even seen it on a coffee shop’s menu, the layered latte apparently is a real drink in which, instead of the steamed milk being poured into the hot espresso, the espresso is poured into a clear mug or glass of hot milk.

If poured at just the right rate and given a few minutes to sit undisturbed, the two substances should separate into these distinct layers, a neat banded gradient from mostly milk at the bottom to mostly coffee at the top.

Here’s how the New York Times has distilled the physics of the layered latte: “When the liquids try to mix, layered patterns form as gradients in temperature cause a portion of the liquid to heat up, become lighter and rise, while another, denser portion sinks. This gives rise to convection cells that trap mixtures of similar densities within layers.”

C’mon, there has got to be more to this than just that old high-school-physics precept “Heat rises; cold falls.” Here, because both liquids start out hot—and, according to the article, the layering sometimes lasts for hours—I have to believe the whole mugful starts and stays at pretty much the same temperature.

Then is it something about the relative densities of hot espresso and hot milk? And what explains why, instead of a uniform blending from light to dark, the concoction settles into these sharply defined layers.

So where do we find the answers? Any of my barista friends out there also happen to be physicists? Or perhaps chemists? Or maybe one of those big shots in the present administration in Washington could just make up something to explain this elegant little surprise of science. Nah...more likely, they’d just deny it; some jive about fake brews. (Sorry.)

* Is there anything so dark, yet so clear, as black coffee? And the smell...oh my, you start thinking of it in the middle of the night.
How could it get any better? Use a clear glass mug, add cream, and watch dusky thunderheads billow in a mahogany sky.
From UNDER THE WILD GINGER – A Simple Guide to the Wisdom of Wonder – Jeffrey D. Willius  


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