Back in San Francisco’s hippie heyday, there was a fair bit of LSD, or acid, being consumed. A lot of it was taken via blotting paper dipped in acid and allowed to dry (the paper was usually perforated so it could be easily torn into little squares). As you might not be surprised to learn, a number of people adorned their blotter sheets with colorful artwork.

Mission resident Mark McCloud has amassed the world’s largest private collection of blotter art, which he calls the “Institute of Illegal Images,” and select pieces are going on exhibit today at FIFTY24SF (218 Fillmore St).

The show is called “Take It Acid Is” and it will feature key examples of actual blotter paper from the Institute of Illegal Images as well as a selection of prints of the artwork blown up, so you can see details that normally aren’t visible to the naked eye.

Of course, if it’s about San Francisco and acid, there’s no way the Grateful Dead aren’t involved, right? Right. McCloud said in a statement that the show focuses on the blotter art that he “obtained or created” throughout his 50 years of love for band.

“This art is intrinsic to the Bay Area and the events that occurred throughout its history that have changed the world’s view of its inhabitants, and the planet for that matter,” FIFTY24SF gallery director Trevor Martin told Hoodline.

As might be expected, McCloud has run into some legal troubles in the past, given the nature of his collection. If you care to learn more about the history of the Institute of Illegal Images, check out McCloud’s website, BlotterBarn.com.

The opening party for “Take It Acid Is” is tonight (Friday, June 26) starting at 7pm.

FIFTY24SF gallery hours: Wed-Sun noon-6pm.