In the summer heat and the noise of a construction site, Renate Rohn paints the light of the Holy Spirit on an apostle's arm in the curved St. James Cathedral sanctuary ceiling. Her hair is damp and a fine sheen of perspiration coats her face as she touches the hairs of the brush to the mural of the Pentecost — Mary in the center with Jesus' disciples on either side, a dove descending from above.

The fine detail of her work — the white gleam in the upturned eyes of Mary or the toenails of the apostles — will be invisible to the Catholics who four months from now will gaze at the mural from their pews 25 feet below. But she feels hopeful that her artistry will convey the awe, mystery and emotion of the picture she is painting.

"Even if nobody sees the details from the pews, I'm hoping the feeling comes through," Rohn said.

The mural by artists from Pittsburgh-based Rohn & Associates Design Inc. is part of the $1 million in liturgical art commissioned by the Catholic Diocese of Orlando in the $10 million renovation, reconstruction and expansion of St. James Cathedral in downtown Orlando. Started in July and scheduled for completion in November, the project is about 65 percent complete.

During the summer, more murals, stained-glass windows, marble columns and floors, and rows of new wood pews will be installed. The Pentecostal mural at the front of the sanctuary is the first to be completed because, like a person painting a room, the artists start at the top and work their way down, said Antonio Aguerrevere, who oversees the renovation for the diocese.

The figures of Mary and the 12 apostles were painted on canvas in the Rohn & Associates' studios, cut out and then nailed and glued to the half-domed ceiling of St. James. The background was then painted around them. As in the biblical passages that describe the Pentecost, a wind blows the clothing of the disciples.

"I keep hearing the wind when I'm painting it," Rohn said. "It's such a fantastic scene."

She is 62 years old and has been doing religious paintings for much of her life, abandoning her studies toward becoming a book illustrator to insteadjoin the family business painting churches, cathedrals, chapels and parishes.

"I was two years into art school when my father said, 'There's nothing you can learn there that you can't learn at home,' " she said. "This is my inheritance. It's a gift from my father. I think this is what I'm supposed to do."

Rohn & Associates has done more than 2,450 religious paintings and murals in the past 50 years, said Rolf Rohn, Renate's brother, who is also a liturgical artist and company director.

Through the years, the artists have become teachers — educating ministers and congregations about how art and liturgy work together, said Rolf Rohn, 66.

Take Mary in the Pentecostal scene, he said. She stands in the center of the picture with eyes turned upward and arms outstretched while the apostles kneel on either side with their hands clasped in prayer or reaching out.

"She is Mary, but she is much more than that. She represents the church here and now," he said.

Renate Rohn is mindful that the art she is creating will outlast the artist. She makes a conscious effort to remove her personal style from the scene she is painting. It must look as original and inspiring 50 years from now as it will when the parishioners of St. James Cathedral witness it for the first time.

"You have to be very conscious of not making something so stylized that it will look dated after a period," she said.

On the scaffolding high above the floor of the sanctuary, Renate Rohn touches the tip of her paintbrush to the paints on her paper plate, mixing the ocher yellow and cadmium orange with the titanium white. With a fine, feathery stroke, she applies the finishing touches to the outstretched robed arm of an awestruck apostle.

Jeff Kunerth can be reached at jkunerth@orlandosentinel.com or 407-420-5392.