If “On the Road to the Summer of Love” at the California Historical Society is like happening upon Jimi Hendrix playing from the back of the Jefferson Airplane’s flatbed truck in the Panhandle in 1967, then “The Summer of Love Experience” at the de Young Museum, through August 20, is like a crowded weekend at Outside Lands 50 years later—with an exit through the gift shop, just to make sure it’s absolutely clear how far we have not come. Snark aside, those who love rock posters will find plenty to admire amid the sprawling exhibition’s 400-plus objects and videos. For many rock-poster fans, the show’s highlight will probably be a small, red-walled gallery about halfway through the exhibition. Conceived by Victoria Binder, who is an Associate Paper Conservator at the Fine Arts Museums of San Francisco, and who contributed an essay to the de Young exhibition’s catalog, the gallery focuses on how posters were printed, how color was used to produce psychedelic effects, and how light could be used to make those effects even more eye-popping. As you enter the gallery, start on the wall to your left, which features a 4-minute video—shot for the exhibition—of renowned poster artist David Lance Goines demonstrating the workings of the Heidelberg offset lithographic press at his shop, St. Hieronymus Press, in Berkeley. Take the time to watch the video before moving to your right, where a wall of posters by Robert Fried, Alton Kelley, Stanley Mouse, Wes Wilson, William Henry, Rick Griffin, and Victor Moscoso are paired with their corresponding sketches, mechanicals, and flats created during the printing process. To the right of that is a wall devoted to color, showing how transparent inks work their magic via Bob Schnepf’s “Tree Frog”; how opposite colors make posters psychedelic via Wes Wilson’s “Flames”; and how, contrary to popular belief, rock posters in the ’60s were not printed with Dayglo inks (the exception being “Keep California Green” by Kelley and Mouse). There are also two fine examples of the split-fountain technique. Finally, you are ready to turn your attention to a wall of Moscoso posters, most of which were designed to be viewed under alternating blue and red lights so that the images on the posters appear to be animated (the first poster in this series was a happy accident). Portals cut into the wall let you view reproductions of the posters in full animation, while the originals have been hung above so that you can compare the static versions to the animated ones. Binder’s gallery is the culmination of 10 years of research, which has included numerous interviews with artists and regular trips to TRPS shows. Her efforts at the de Young, including her catalog essay, have resulted in what’s almost certainly the definitive description of how rock posters were produced in the 1960s by printers such as Levon Mosgofian of Tea Lautrec Litho, Frank Westlake of Bindweed Press, and Ewald Treude and Louis Longwenus of California Litho Plate, as well as people like Errol Hendra, whose Camera Shop worked closely with artists to help them prepare film for the presses. While this scholarship may not be as top of mind to rock-poster collectors as edition numbers, print runs, and whether a band listed on a poster cancelled at the last minute, it’s every bit as important. Indeed, until now, it was the missing piece in the rock-poster narrative.