The Swiss Water Process is a patented decaffeination method that uses only water to remove 99.9% of a coffee's caffeine content. Heat and time are also employed, but clean water is the only added ingredient.

It's complicated, but the short answer is diffusion. Swiss Water explains that green coffee refers to the processed seed of the coffee tree fruit. Coffee is a flowering shrub that produces fruit. Coffee is soaked in their proprietary Green Coffee Extract ("GCE"), containing all the water-soluble compounds found in coffee, except for the caffeine. The solution is heated, so the coffee beans swell and become porous. The caffeine molecules move out of the swelled coffee and into the GCE through osmosis, while the volatile compounds that affect things like flavor and Aroma refer to sensations perceived by the olfactory bulb and conveyed to the brain; whether through the nose or "retro-nasally": The aromatics of a coffee greatly influence its flavor profile and come from the perception are left in place. The process is repeated until the coffee is 99.9% caffeine free.

The Swiss Water method uses no chemicals whatsoever. In contrast, many other decaffeination methods employ chemical solvents like methylene chloride ("MC" decaf) and ethyl acetate, but one uses a mild type with low toxicity. It sometimes imparts fruity flavors to the coffee. This is a "direct contact method" of decaffeination since the solvent chemical that washes ("EA" decaf – either naturally or synthetically derived).