Seated around an ash-stained coffee table below a glowing chandelier in Mark McCloud’s dusky parlor on a rainy Saturday morning in October, four friends passed around a joint, trying to define in simple terms the three-story Victorian on 20th Street.

“It’s an archival museum of psychedelic art. Our friend here is the curator,” proffered Arthur Round, an older man cross-legged in a wicker chair. The parlor is plastered with approximately 350 pieces of framed blotter art and guarded from prying eyes by heavy black curtains, making the space feel like a vault or secret subterranean headquarters.

Dubbed the “LSD Museum” by some of his fans, McCloud’s collection includes more than 33,000 sheets and individual tabs of blotter paper imprinted with pop culture images and used to transmit doses of LSD. He calls it the “Institute of Illegal Images.”

Until Nov. 25, dozens of the pieces, as well as some digitally enhanced reprints, are on display at Ever Gold Gallery in the Tenderloin.

McCloud’s mission is to preserve a “skeletal” remnant of San Francisco’s drug-induced 1960s legacy, “so maybe our children can better understand us,” he said. Collectors in the business consider him the bearer of the world’s largest cache of psychedelic blotter art and its foremost historic authority – an institution unto himself.

“His collection has got to be the most extensive in the world. He’s followed it from the beginning,” said Phil Cushway, owner of ArtRock, one of the primordial concert poster outlets, in SOMA. Cushway occasionally sells blotter art for McCloud. “What he does, he does seriously.”

McCloud is 56 years old with dark greasy hair and a rakish grin. He pads around his weathered Victorian on 20th Street wearing a black faux-leather fedora, loose-fitting cotton pants and slip-on footwear. Reading glasses and a house key dangle from his neck. His T-shirt reads “LSD underwater tours. Dive into your sub-conscious.”

McCloud said he’s intent on protecting the meaning of acid rooted in the user’s experience – largely to counterbalance the stigmatization of the drug by government officials.

The problem, he’s decided, is that bureaucrats haven’t tried the trip. Billed “Tranquilizers for a Drug Enforcement Agency gone rogue,” McCloud’s current exhibition is a proud middle finger at the federales whose promise of life behind bars he escaped – twice. In 1992 and again in 2001, agents arrested McCloud on charges of conspiring to distribute LSD. The breadth of his collection spawned suspicions that he was a drug kingpin.

In the latter case, federal agents descended on his Mission home and seized several hundred framed sheets from McCloud’s living room, only to find some had never been spiked with acid. Others that may have been had since been chemically neutralized. Juries in Texas and Missouri – where drug busts turned up blotter that agents linked to McCloud – acquitted him both times.

“I was terrified,” recalled Cushway, who testified at the second trial as to the artistic significance of McCloud’s collection. “[The jurors] were not very sympathetic.”

The indexed evidence from the trial decorates McCloud’s parlor, and some of it was selected for the show at Ever Gold. The DEA marked each confiscated piece with masking tape and a number. Some of the sheets, the ones measuring 8.5 by 11 inches, contain 1,000 tabs or more.

In the 60s, conventional wisdom denoted the bar for achieving clinical insanity at 200 hits of LSD, according to McCloud and Rounds. Ask them how many they’ve taken in about 40 years and they’ll tell you less than that amount.

In the same moralistic manner many San Franciscans pontificate on the health benefits of marijuana, McCloud and his friends tout the merits of acid.

“We’d take it for a common cold in the 60s,” Round said. “If I have any regrets it’s not doing drugs enough.”

What else will it cure? Anxiety, depression and “marital problems,” Rounds said.

It’s been good to McCloud for a long time.

Born and raised in Argentina, McCloud began experimenting with psychedelics during adolescence while attending Webb School for Gentlemen, a boarding school in Claremont, Calif.

But it wasn’t until five days after his 18th birthday – Dec. 9, 1971, to be precise – as a freshman pre-med student at University of Santa Clara that McCloud experienced “death and rebirth.” It came in a sugar pill laced with a potent type of LSD called “Orange Sunshine.” McCloud reflects fondly on that day as a “rapture experience.”

“My reason for being here became clear after that … to come speak to you about all these people who are doing all this unnecessary suffering for a war on drugs.”

McCloud switched focus from medicine to art, and after college studied Renaissance art in Paris before settling in San Francisco. He put a down payment on his Mission home in 1983 using money from a National Endowment for the Arts grant. He served as vice chairman of the Artist Board at San Francisco Art Institute from 1977 until 1987, the year of his first blotter art show.

McCloud got serious about collecting blotter in the early 1980s, and started framing and hanging the works instead of sticking them in the cold, dark freezer, where they were likely to get eaten on impulse.

“I realized, ‘This is a good way to save them,’ ’cause you can’t swallow the frames,” he said.

By stockpiling the sheets, McCloud is essentially positioning himself as a force the mainstream art community will have to acknowledge one day, Cushway said.

“It is not recognized as [folk art] now,” he said. “But eventually it will be.”

The bulk of the collection remains tucked away, out of reach from harmful ultraviolet light and the government.

“You think I’m kidding but they’re coming again,” said McCloud, referring to the feds. “This is where the fire stopped in 1906. These are the first three homes to survive the fire. This is where the fire will stop again.”

What fire?

“The senseless fire of throwing everyone in jail for seeking consciousness.”