AUGUSTA — Lithgow Public Library’s 120-year-old stained-glass windows are fully restored and back where they belong.

On Wednesday, the installation commenced at the library after Richard Bolton and the team at Stained Glass Express in Manchester had spent about 20 months restoring 28 windows.

The window installation comes following completion in August 2016 of the library’s landmark $11 million renovation and expansion at Winthrop and State streets.

Bolton said the medallion-style windows, most of them about the size of a large serving tray, typically took between 120 and 160 hours per window to restore.

Bolton has said the meticulous work on the Lithgow windows typically took between 120 and 160 hours per window to restore.

“Toothbrushes, water, a small amount of Simple Green (diluted), patience and elbow grease” Bolton said of how he cleaned the unpainted stained glass. “It’s a very labor-intensive craft. There is no getting around that.”

Elizabeth Pohl, director of Lithgow Library, has said the windows were so dirty and in such poor condition it was hard to tell what their true colors were. Pohl said the $116,000 cost of the stained glass windows’ restoration is being paid for with privately raised funds. Those funds included $43,000 raised about 10 years ago and held by the Friends of Lithgow Library for the project and $73,000 raised as part of a fundraising campaign to help pay for the cost of the library expansion.