BIRMINGHAM — As color-coded zoning maps go, one created in 1926 for the City of Birmingham Zoning Commission appears easy enough to understand.

Dark hues of yellow and pink designate industrial use. Royal blue, commercial districts. Pastel yellow and pink — some patches overlaid with diagonal lines — identify residential neighborhoods.

The meaning of those diagonal lines isn’t stated on the map’s key, but what was plainly understood then, in Jim Crow-era Birmingham, is that they represented areas where blacks, by a local law, were allowed to live.

Now, 86 years after it was created, the map is being cleaned and restored. The Friends of the Birmingham Library, a nonprofit organization, donated $1,500 for the project, said Benjamin E. Petersen, head of the Southern History Department at the Birmingham Public Library.

“We are very proud to have been able to make a grant to help conserve and digitize a map which our Southern History librarian determined was uniquely important to the library’s Southern History collection,” said Pat Rumore, president of the Friends group.

The map is 78 inches long and 26 inches wide. It is one of only two copies known to exist; the other is at Birmingham City Hall, Petersen said.

John Bertalan, of Conservation Technologies Inc., a Birmingham company, is the conservator who is cleaning and restoring the map.

It was printed on paper and hand colored, Bertalan said, then glued to a linen/cotton blend cloth. Landmarks are easy to spot — Birmingham-Southern College, the state fairgrounds, East Lake and Avondale parks, Sloss Furnaces.

Conserving the map may look simple to an untrained eye, but it’s a painstaking process that requires a precise knowledge of materials used to make, color and repair the map. Determining that can take a bit of detective work, but it’s necessary so that the map isn’t damaged.

“We’re identifying and testing every color,” Bertalan said.

Knowing who made the map, in this case, the engineering firm of Morris Knowles Inc., of Pittsburgh and Cleveland, means researchers can find what materials were used to make it, Petersen said.

Seven types of dye were used to color the map and two kinds of tape to make repairs, Bertalan said. To remove tape, for example, he has to make sure the solvents used won’t react adversely with the dyes and paper.

Section by section, the map is cleaned and where necessary, repaired. A section that includes the Inglenook neighborhood north of today’s Birmingham-Shuttlesworth International Airport was patched at some point, so Bertalan is repairing that repair.

The project is in its “very early stages. I’ll be happy if it’s done by the end of the year,” Bertalan said. “Until you begin work on something like this, you can’t know what the problems are.”

Once Bertalan’s work is finished, the map will be encapsulated in protective mylar and sent to the University of Alabama’s Cartographic Research Laboratory to be digitized. Eventually, possibly by next summer, it will be available in the library’s visual collection through its website, bplonline.org, Petersen said.