The Shadyside Presbyterian Church in the City of Pittsburgh holds a striking mosaic of the Transfigured Christ. The mosaic was installed in 1938 by Rudolf Sheffler, but by 2020 it was in need of a church mosaic conservation treatment. Conservator Marcin Pikus, Conservator of Stone Sculpture and Architectural Features, of McKay Lodge Conservation Laboratory first performed an assessment.

Rudolf Sheffler, Transfigured Christ, 1938, before treatment

The mural is approximately 23 by 20 feet, and it is located in the main apse of the Church. Multi-colored stone and glass tesserae embedded in a cementitious brown-gray colored mortar create the overall image. The upper half-dome portion of the mosaic depicts Christ on a golden, glimmering background, while the semi-cylindrical niche depicts richly ornamented curtains.

The mosaic also features an inscription located on the proper left side of the mosaic. The message reads: “IN LOVING MEMORY OF FLORENCE AIKEN SMITH”.

The message, “”IN LOVING MEMORY OF FLORENCE AIKEN SMITH”, image is enhanced for clarity

Conservator Pikus felt that the mosaic was in good condition overall, with only minor issues, but some mosaic conservation treatment was required to return it to the intended appearance.

The surface of the mosaic has an accumulation of dirt, before treatment

There were numerous missing tiles in both the lower and upper sections. Missing mortar was also evident between the edges of mosaic and adjacent stonework on each side. Dust, grease, grime were observed on the surface, especially the lower portion of the mosaic.

Mortar was missing between the mosaic and wall before treatment

Conservator Pikus performed a treatment for the church mosaic. First, the mosaic was cleaned with an aqueous solution to remove any dirt and accumulated dust. The surface was lightly scrubbed with a soft, synthetic scrub brush and a microfiber cloth. Remaining residues were rinsed with clean water then wiped dry with microfiber cloths.  The areas adjacent to the bench behind the altar table were cleaned with steam as needed.

The wall is cleared with steam to remove tenacious grime and dirt

Missing areas were replaced with new tesserae that matched the existing design and color.  Areas with missing mortar were re-pointed with conservation-grade mortar, and the adjacent limestone was cleaned with steam to improve the appearance.

Missing mortar is now replaced after treatment

After treatment, the mosaic might not seem all that different from afar; however, the surface of the mosaic is free of dust and dirt, enhancing the colors. Damaged joints were repaired and missing tesserae were replaced to create a more visually continuous and stable surface.

Rudolf Sheffler, Transfigured Christ, 1938, overall after treatment

The mosaic is installed in a dry and stable environment which is excellent for its long-term preservation, and only routine surface cleaning is required.

To learn more about the Shadyside Presbyterian Church, visit their official website.