Last weekend, the Chicago Cultural Center unveiled the restored Grand Army of the Republic dome. Installed in 1897 as a feature of the Chicago Public Library, the 40-foot diameter Tiffany-designed stained-glass dome had become covered in grime and paint, and cut off from the natural light that brought out the brilliant colors of the glass. Using a $15 million donation, the Cultural Center hired Daprato Rigali Studios, a 160-year-old restoration firm that has also done work on Holy Name Cathedral. Bob Rigali, the great-grandson of founder Joseph Rigali, talked to Chicago magazine about the restoration process, which he called one of the most significant in his company’s history.

You said you’ve been in business for 160 years, but this project was particularly important. Why is that? What’s the historical importance of this dome?

I think two things. One is the design was by Louis Comfort Tiffany. Then the actual people that took his design, fabricated, and installed it were a famous stained glass studio, Healy and Millet. So it was done by two extremely famous people.

In what condition did you find the dome?

It had been neglected for 50 years. So there was a lot of soot, a lot of dirt. And then they had done some painting up in the attic area. There was a lot of overspray, and that got on some of the glass. Above the dome there used to be chicken wire glass that let light through. At some point in the ’60s or ’70s they cemented that whole dome off with cement panels, so there wasn’t any more natural light coming through there, so part of this project was to remove the cement panels and put back a skylight above this dome.

Did you have to disassemble the entire thing and take it all back to your studio?

Yes. There were over 60,000 pieces of glass in the dome itself. Each piece, we tried to preserve as much of it as possible. So it came out in sections. We divided it up into a pie, which was eight sections, and each of those sections had approximately 10 sections per that pie. We took each one of those sections out, brought them back to the studio.

At the studio, the work we performed was, first of all, photo documentation with light and then without light, and then we’d get rubbings of them. We put them down on the table and we took a paper and we’d use charcoal and do a rubbing, so we’d have an exact replica of all the lead lines in the glass. And then from there, we disassembled it 100%: We’d take all the lead apart and clean the glass, and then we needed to find exact replicas of the glass, the pieces we needed to replace. Then we needed to find the exact match of the lead. There were three different types or sizes of lead that we had to find to match that. So that process took about a month, month and a half. And once we had all the materials, we had approximately 10 craftsmen working for almost one year.

This was installed in 1897. Is this the first time it’s ever been restored?

There were some general repairs done to it, but it hadn’t been taken out and removed from the frame.

Compare when you saw it for the first time to the way it looked when it had natural light coming through.

The colors are spectacular, natural light coming through there. We had no idea what the colors were when we originally went up and looked at it, because it was so dirty. There was a thin layer of paint on it. It really is brilliant now.

What will visitors to the Cultural Center see of the dome that they haven’t seen before?

Really, the magnificent colors and the design. You couldn’t see the design, it didn’t register through. There’s over 60,000 pieces, there’s over 3,000 jeweled pieces of glass that are just brilliant with the light coming through them. He designed a dome with a lot of intricate curls, a lot of lead lines that circle beautiful jewels, so when the natural light comes through, it sparkles.

When you uncovered some of the grime, you found the Tiffany design finishes on the frame. What do those look like?

They’re more subdued colors, greens and bronze.

Were those visible at all before?

No, they were painted over. What we uncovered is a dark green. Before, it was painted a cream color white.

Do you expect this to become a tourist attraction?

I would definitely think it would be on everyone’s radar at this point. It just looks magnificent. I’ve been doing this for 40 years. I don’t think there’s a project where there has been such a detail-oriented project to preserve what was created at one time. I really think that it’s going to be a big draw for the city and throughout the country because of that.

Have they talked about how they’re going to treat it differently, to make sure it doesn’t get into a degraded condition again?

They’ve done some things where they’ve vented the area, they’ve got heating and cooling now above it, so it’s just not this intense heat zone anymore. They tried to take it from a standpoint of, how can we maintain this for the next 100 years, where climate and environment are a large part of it? And then go every five to 10 years, depending if needed, and do a light cleaning.

How long can these things last?

Easily hundreds of years. It’s lasted this long in pretty decent shape.

You think it’s good for at least another 125 years?

Fair to say, yeah.