In Fermentation Technology by Ray Medina, on page 78 it says the whirlpool was developed in brewing by Henry Ranulpf Hudston in 1960 when he worked for Molsen. It is based on the tea leaf paradox observed by Einstein.
Can’t find a reference to when hops were added. Mitch Steele, formerly of Stone Brewing Company, has been one of the foremost experts on this technique, and has discussed it in numerous forums, including his book, IPA: Brewing Techniques, Recipes and the Evolution of India Pale Ale, presentations at the National Homebrewers Conference and in an article in the November/December 2013 edition of Zymurgy magazine.
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