Physics of Decafe Coffee

Some musings..

Sujatha Ratnala
2 min readMay 25, 2023

Last weekend, was having decaf coffee at a friend’s place and wondered.. How do they wash off caffeine? It seems incredibly crazy that the coffee granules have by some magic lost their water soluble caffeine.

The horses of the mind began to wander. We had this chapter in school on Seperation of Mixtures.

In my student mind, my mom was a master of this Science. With a tossing winnow, seperate the light dust from the rice.. With a sieve, eliminate the big particles.. With a steel filter, separate the tea leaves from the Chai. And the ritual of whitening the Saturday White Uniforms by dipping them in a tub of Indigo Neeli water.

And in school we had this Chromatogram Experiment, where color pigments from the flowers were separated using a bookmark sized piece of adsorbant paper. Could it be this? Using some sort of surface to absorb the caffeine?

Another household separation hack was with oils and solvents. Acetone for removing Nailpolish, and oils for scrubbing out kajal and colors.

I could not contain the suspense of Decafe Coffe anymore and eventually Googled. And looks like the guess work was partly right.

Image credit: Shutterstock

The chemical formula of caffeine is C8H10N4O2. It occurs in the seeds, leaves, and fruit of several plants.

History has witnessed Decafe Coffee in 1905 as an act of Serendipity, when a shipment of coffee beans belonging to a German merchant accidentally soaked in the sea water. And the Decaf Industry began to thrive. So much for the caffeine..

Chemical Decaffinetion involved solvents like Benzene, or Methyl Chloride, or Carbon Dioxide to wash of the Caffine.

There is another Green method without chemicals, where the Coffee beans is soaked in Hot water to let go of its flavors and caffeine. A charcoal filter is then introduced to selectively remove the caffeine from flavored waters. And this water is added to another batch of unroasted coffee beans.

There is flavor and caffeine inside the beans.. There is flavor outside the beans. Due to diffusion and act of Equilibrium, the caffeine rushes outside the beans..

Quite a balancing act to quench the Human appetite while resting the horses of the adrenaline.



Sujatha Ratnala

I write.. I weave.. I walk.. कवयामि.. वयामि.. यामि.. Musings on Patterns, Science, Linguistics, Sanskrit et al..