Do you read the ghosts?

Once you start to notice the ghosts, you see them everywhere.

They float over your favorite intersections, sometimes clearly visible and sometimes just a wisp of fading color, clinging to their messages, directing us toward long-gone ice suppliers and automotive shops.

While ghost signs — those old fading illustrations, usually on walls and usually advertising something — are not exactly the stuff of stand-along tourist attractions (yet) in the United States, they are becoming increasingly collected and studied here and especially in England. In many places, including Portland, they are protected by inclusion in historic districts that require special permission to remove or paint over the images.

In New York City they have become nearly trendy, being digitally collected and stored on websites.

They may be artifacts now, but boy, back in the day.

The sign painters, called "wall dogs," often traveled from job to job, using lead paint that clings to walls for decades. Portland, especially in the Old Port, has one of the better mediums for such work — nice wide brick walls.

Typically, the deal was that a "company man" did the advance work, offering a small sign for the wall's owner if the space could be made available. The urban painters, say historians, usually stayed in the city while country crews painted ads on all those roadside barns. Some of the signs were traced using paper and chalk to outline the ad, but many were freehand reproductions of small cards.

The wall dogs were the latest in a long, long line. The use of walls for painting your messages dates back at least to ancient Egypt, and the famously preserved ruins at Pompeii have painted lettering that can still be read today, including elaborate ads for what is famously referred to as the world's oldest profession.

Most of the really good ghost signs were painted in the heyday of hand painting before about 1950, when the economics of printing and municipal sign codes pushed outdoor ads toward billboards and posters.

Deb Andrews, the city's historic preservation program manager, says the ghost signs have become a distinctive feature of the city, especially in the Old Port but in other historic areas as well.

"It's part of the patina of a building," she explained, adding that while destroying a ghost sign is not specifically prohibited, many are protected because the building they grace are in an historic preservation zone. That means such changes have to be reviewed by a preservation committee, and owners are "encouraged" to keep the images.

"For the most part, we find property owners enthusiastic about keeping them," said Andrews. "It's really interesting to walk down the street and read about all the previous uses."

Like many of us, Andrews pauses only briefly before remembering where her favorite ghost signs are: at Gorham's Corner, near the John Ford statue where an historic building is graced with both authentic ghost signs and newly painted images in the old style.

Actually, re-painting the images is a hot-button issue among ghost sign fans, with many people insisting that "preserving" doesn't mean restoring because that reduces the iconic fading. Eventually fading away, they argue, is part of the charm.

At one corner of Fore Street on Boothby Square in Old Port, employees at the Watson & Worthley salon work inside walls that hold one of the city's more distinctive signs, directing viewers to WILLIAMS BROS ICE.

While one employee praised the ghost signs for their ability to remind us that the area was once a working waterfront, another said the one thing she knew about them is "I know you can't touch them."