Why Outdoor Marble Needs Special Care

Marble has been used to create some of the world's most impressive sculptures and buildings throughout history. It is a relatively soft and porous stone, making it ideal for carving intricate details that bring the stone to life. It is also known for being quite durable. 

Guild Park is home to a number of carved marble features. One of our favourite marble pieces is the sculpture named Musidora, found outdoors in the south gardens west of the Guild Inn's patio. She was sculpted in 1875 by English artist, Marshall Wood and is thought to be the oldest artwork on site. 

Exactly when and how this life-size figure arrived at Guild Park is unknown. Photos and notes about the Guild show she was installed in the park's sculpture garden by 1982.

When Musidora was created, deterioration from exposure to the elements and vandalism were never intended to be part of her lifecycle. This begs the question: How well does marble hold up outdoors?

It is common for marble sculptures to be finished with a protective coating, but this rarely provides sufficient protection against years of exposure to the elements. 

The main culprit outdoors is moisture. Moisture draws particles deeper into the pores of the stone. Soluble mineral crystals and acidic pollutants in the air travel through the stone, causing cracks and material loss. Moisture also attracts microorganisms to the stone's surface. The freeze-thaw cycles of our seasons are especially unfriendly to marble. 

The stone’s white colour can also become discoloured by airborne pollutants, soiling and surface organisms. A dark gypsum crust can develop if the sculpture is not cleaned regularly. Furthermore, the smooth surface can become a tempting canvas for vandals, as Musidora has unfortunately experienced before.

Musidora, Guild Park's 150-year-old marble sculpture. Left: the sculpture as illustrated in a 1982 Guild publication. Centre: recent view showing weathering damage and surface discolouration. Right: the back of the sculpture, where traces of graffiti remain visible despite earlier conservation treatment.

Today, Musidora shows signs of cracking, loss of detail, staining and vandalism that have accumulated over many years. The accompanying photographs illustrate this deterioration, including traces of graffiti that remain visible on the back of the sculpture despite earlier conservation treatment by the City of Toronto.

This reflects the City's limited maintenance resources for the park's artworks and artifacts. Ideally, marble artworks and artifacts would receive regular cleaning, along with a winterization and moisture mitigation plan.

Cleaning marble sculptures can be carried out by City-approved conservators using gentle methods such as poultices, biocides, washing and careful mechanical cleaning. Areas where material has been lost can also be repaired by infilling with appropriate conservation materials, such as resins.

Musidora is not the park's only marble artwork facing these challenges. Other marble features experiencing concerning levels of deterioration include the century-old Bank of Nova Scotia columns from that downtown Toronto building built at 39 King St. W. in 1903. 

When that original building was demolished in 1969 to make way for Commerce Court, the original marble columns and other features were saved, moved to the Guild and became part of the Spencer Clark Collection of Historic Architecture.

Marble columns from Toronto's former Bank of Nova Scotia (1903), now at Guild Park, showing typical signs of deterioration. From left: cracking, staining and surface deterioration, and crumbling stone.

Today, these marble columns show significant cracking and crumbling at the base and midsection, as well as staining caused by minerals and biological growth. The City’s Public Art team is currently monitoring the condition of the columns.

Lilla Lengyel

Graduate, Fleming College

Cultural Heritage Conservation & Management

Director, Friends of Guild Park