Holy plastic slab! - It's not superpowers that make comic book heroes untouchable today. It's the stiff sleeves that render them unreadable and more valuable.

A company in Sarasota, Fla., has created a sensation among collectors by taking their comic books, both rare vintage issues and brand-new ones, and encasing them in plastic slabs that make them both unreadable and instantly more valuable.

The Captain Marvel and Donald Duck comic books that arrive at the offices of the Certified Guaranty Co. are treated like archival treasures of the highest order -- armed sentries guard the lobby, technicians and appraisers wear latex gloves as they carefully examine each page and a sophisticated sonic device is used to seal the books up in the sturdy plastic containers that some collectors call "coffins."

Depending on the age and pedigree of the book being appraised and "slabbed," CGC charges from $12 to $1,000 for its services and, in upcoming months, the 7-year-old company will slab its 1 millionth comic book. That book may be a 60-year-old issue of Detective Comics that costs as much as a Porsche but it could also be the latest $3 issue of World War Hulk -- about half of the books that come to CGC now are fresh from the printer and probably 80% of them have never been read.

All of this seems like heresy to many old-line comic book purists.

"It's changed the nature of the hobby, it's turned comic books into a medium of exchange instead of a medium of entertainment," groaned James Friel, who works at Comic Relief, the longtime landmark store in Berkeley. To Friel, who has been collecting comics since 1958, "it makes these books a sealed-up commodity. You can't read them. It makes me sad. Some of these books will be sealed up forever."

Frank Miller, arguably the most important comic book artist of the last two decades, has seen plenty of fans lock up his books in the slabs in recent years and he shakes his head at the whole concept.

"I think it's all pretty silly," said Miller, whose graphic novels "300" and "Sin City" have led to major Hollywood success stories. "But I'm of a generation that love the feel and smell of these ephemeral old leaflets. . . . Maybe it will get to the point where I can put out comics that have blank pages inside -- just covers -- and no one will notice."