Green + Green = Pink

Here’s a tale from my travels. File the genre as “Mystery/Snacks.”

It was a fine February day, and the math department at Baylor had laid out a lovely snack table, including two beverages:

  • Hibiscus green tea (which was a deep, mossy green); and
  • Limeade (which was a pale, electric green).

Both looked pretty tasty.

“Does anyone ever mix the two?” I asked. “Like an Arnold Palmer, but… green?” Folks shrugged and shook their heads. So I decided to give it a shot.

And then…

In a room full of theoreticians, we soon developed plenty of conjectures. Perhaps it was an acid-base reaction. Perhaps the pink substance was there all along, somehow. Perhaps someone was pregnant.

(This last theory came from the department chair. Visionary leaders do not shy away from strange theories.)

Plenty of conjectures, but no answers.

So I reached out to Zoe’s Kitchen, the creators of these chemically active beverages, and pleaded for their help. An employee named Maya replied:

I looped with our Food Safety Quality Engineer here [someone named Zach] at Zoës Kitchen and he let me know that this change of color has to do with the pH of the mixture. Hibiscus is sensitive to acidity and is red/pink at low pH (i.e. higher acid) and blue/green at high pH.

Someone on Twitter elaborated with a link to this image:

The shoe-flower (Hibiscus rosa-sinensis) extract as an indicator at different pH 

Why, then, does Green + Green = Pink? We’ll take it one step at a time.

The first “green” is green tea, which tends to be basic (various online sources put its pH between 7 and 10).

The second “green” is limeade, which tends to be acidic (most lemon/lime drinks seem to have a pH around 3).

And the pink – well, that’s the hibiscus in the green tea, reacting to its newly acidified environs, and thwarting my dream of a Green Arnold Palmer.

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One thought on “Green + Green = Pink

  1. I have done this in my science classes to kick off the pH unit. Pea flower tea also works well, going from a beautiful blue to a purple. We also discuss hydrangeas afterward.

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