acid test

plural acid tests

1. chemistryA test involving the reaction of an acid with another chemical.
2. figurativelyA rigorous test or appraisal of the quality or worth of something.

   The Iran war – barely mentioned during this visit for fear of eruptions – is an acid test.

   2026 May 2, Simon Tisdall, “The king went to Washington to save Britain’s bacon. He may also have shown the US how to save itself”, in The Guardian, →ISSN

   4 more examples

   [H]e reflected that few professional beauties could have stood, as this woman did, the acid test of that mercilessly brilliant morning.

   1912 October, Louis Joseph Vance, “The Spy”, in The Destroying Angel, New York, N.Y.: A[lbert] L[evi] Burt Company, →OCLC, page 152

   "Eggs, Parker," said Freddie solemnly, "are the acid test!" / "Yes, sir?" / "If, on the morning after, you can tackle a poached egg, you are all right. If not not. And don't let anybody tell you otherwise."

   1920 April 10 – August 28, Pelham Grenville Wodehouse, chapter 1, in The Little Warrior [Jill the Reckless], New York, N.Y.: George H[enry] Doran Company, published 8 October 1920, →OCLC, section 1, pages 7–8

   The acid test: will the British public abide by such stringent guidelines about where they should stand, walk or sit in our stations and on our trains, when they have been used to a turn-up-and-go railway where they enjoyed freedom having bought their ticket?

   2020 May 20, Stefanie Foster, “Comment: Safety First: Now More than Ever”, in Rail, Peterborough, Cambridgeshire: Bauer Media, →ISSN, →OCLC, page 3

   This was the acid test – at least before Sunday's final with formidable Italy – and they came up with the goods not only in the context of Euro 2020 but also in demonstrating their character and big match mentality.

   2021 July 7, Phil McNulty, “European Championship – Semi-final: England 2 – 1 Denmark”, in BBC Sport, archived from the original on 12 Apr 2023

3. broadlyhistoricalIn the 1960s, a party based around the use and advocacy of the psychedelic drug LSD (known in slang as acid).

   The Pranksters had just held an Acid Test at the Fillmore Auditorium, a big ballroom in the middle of one of San Francisco's big Negro slums, the Fillmore district. It was a wild night. Hundreds of heads and bohos from all over the Bay area turned out, zonked to the eyeballs.

   1968, Tom Wolfe, The Electric Kool-Aid Acid Test, New York, N.Y.: Farrar, Straus and Giroux, →OCLC, page 253