What it takes to clean industrial soot and grime from a Pittsburgh church's murals

MILLVALE, Pa. — How do you conserve 80-year-old murals that have accumulated decades' worth of soot, salt and other deterioration?

Slowly and carefully, using everything from scientific analysis to seaweed extract to everyday tools — like cosmetic sponges and shish kebab sticks.

That was the approach taken by a conservation team as they labored on a section of murals at St. Nicholas Croatian Catholic Church near Pittsburgh.

The walls and ceiling of the church are covered with an acclaimed set of murals painted by the late Croatian American artist Maxo Vanka in 1937 and 1941. They mix religious imagery with dramatic depictions of war, immigrant life, industrial hardship and moral contrasts — justice and injustice, greed and generosity.

The Society to Preserve the Millvale Murals of Maxo Vanka has been working for the past 15 years to conserve the paintings, one section at a time.

Over the past three years, a crew of 16 has worked intensively on the upper church. From January through May, that work focused on the upper-right walls and ceiling — including an Old Testament panorama featuring Moses and portraits of St. Matthew and St. Mark. The workers cleaned off grime, extracted corrosive salts, carefully reattached peeling paint and delicately added pigments where they had been lost.

''I found art conservation to be a good mix between art appreciation and science,'' said Naomi Ruiz, a wall paintings conservator overseeing this year's work.

The project began in January, when workers installed a 32-foot-high (9.8-meter-high) scaffold to provide close-up access to the murals.

Cleaning off decades of pollution

In the initial days, the conservation team brushed and vacuumed off surface dirt and soot. Then they used wet cosmetic sponges and thin cotton swabs to clean surfaces and grooves.

Much of the grime, they surmise, resulted from day-to-day atmospheric pollution, ranging from Pittsburgh's once thriving steel mills to nearby highway traffic. The challenges are greater on one side of the church, which is damaged from exposure to more sunlight, which means more fluctuations in temperature and relative humidity.

Workers used fine tools to reach inside smaller indentations. Before long, they'd gone through thousands of soot-covered sponges.

Soon, the workers began to see the images becoming clearer, with gray sections returned to the original white painted by Vanka.

''It's really fascinating, especially to see from below, a lot of these details that were lost coming back, and seeing what his initial vision was,'' conservation technician Christina Cichra said.

Chemistry, color and cleaning

Workers also cleaned the aluminum leaf that forms backgrounds, as in the arch-shaped one behind St. Mark and St. Matthew.

They used a solution with neutral pH — neither alkaline nor acidic, both of which would damage the material.

Parts of the aluminum leaf have deteriorated entirely. The team's original idea was to replace those sections with new leaf, but it was too shiny and didn't match. After some experimentation, they decided on a mixture of watercolor and other materials.

''This was able to give us the right amount of sheen and tone to blend in with the original aluminum leafing,'' Ruiz said.

To remedy paint loss, the crew used pastels and watercolors to fill in certain areas, while retaining Vanka's original brushstrokes.

The team took a conservative approach, filling in only where necessary and using materials that can easily be removed, in case they or later conservators decide a different approach is needed. A primary goal is to reveal as much as possible of the original art.

Salts, poultices and seaweed

A major challenge is posed by sulfate salts, which occur naturally but can be especially prevalent where there is more air pollution, Ruiz said.

The salts react with moisture in the walls and cause deterioration.

The crew attached poultices — bandage-like containers of fine cellulose fibers — to affected spots. One type of chemical compound in the poultice leeches out the salts, a process repeated several times. Still more poultices were applied, this time with a different compound that strengthens the plaster.

In some areas, paint had curled, flaked or cracked. Workers gently reattached it with funori, an adhesive derived from a seaweed, and use a tacking iron to help secure the paint.

The preservation society, meanwhile, has worked with the parish on improvements such as roof repairs and a new climate control system to help prevent future damage from the elements.

It's conservation, not restoration

Ruiz prefers not to use the word ''restoration'' for the project, although some of the work technically fits that category.

She said ''conservation'' is a more comprehensive term, which includes everything from documentation to preventive care while making Vanka's original work as visible as possible.

''We want to really reveal what he did,'' Ruiz said. ''That's what's most important to us.''

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