Conservation Corner: Living Colours on the Stones

When you admire one of Guild Park's historic architectural fragments or hand-carved sculptures, you may notice patches of red, orange, yellow, green or black on the stone surfaces.

What’s causing this discolouration? Many visitors may recognize the familiar green tinge of lichen, but lichen can appear in a surprising range of colours and is sometimes mistaken for paint, dirt, residue from a flare or smoke bomb, or other types of surface staining.

For the curious observer, the photographs below show two Guild Park stone artifacts, alongside magnified views of the colourful lichens growing on their surfaces.

Lichen is a fascinating organism. It is neither a plant nor a fungus alone, but a partnership between living organisms that function together as a single life form. Lichen thrives on surfaces such as stone, wood and soil where moisture, minerals and sunlight are available.

While lichen adds colour and visual interest to historic stonework, it also presents a conservation challenge. Over time, lichen will gradually damage the surface of stone artifacts. The acids produced by the organism slowly break down calcium carbonate found in materials such as limestone, sandstone and marble. These relatively soft, porous stones were widely used for sculpture and buildings and can be found throughout Guild Park's collection of historic architectural fragments and artworks. As a result, fine details, carved surfaces and original textures can slowly deteriorate.

Fortunately, this process usually occurs over many years. However, lichen is only one of several threats facing Guild Park's heritage collection. Weathering, water penetration, freeze-thaw cycles, biological growth, graffiti and accidental or deliberate damage all contribute to the gradual deterioration of these irreplaceable artifacts.

Guild Park contains one of Canada's most significant collections of rescued architectural fragments and outdoor stone sculpture. Preserving these pieces requires ongoing monitoring, conservation expertise and periodic restoration.

One of Friends of Guild Park's continuing priorities is raising awareness of the conservation challenges facing these artifacts and encouraging the investment needed to protect them for future generations.

The next time you visit Guild Park, take a closer look. The colourful patches on the stones may be beautiful, but they also tell an important story about the ongoing care required to preserve the park's remarkable heritage collection.

Lilla Lengyel

Graduate, Cultural Heritage Conservation & Management, Fleming College

Director, Friends of Guild Park

Living Colours on the Stones:Two of Guild Park's notable artifacts with multiple close-up views of lichen growing on their surfaces. Top: Lichen on this Toronto Star building fragment appears as a red stain. Bottom. The column capital is discoloured by a lichen that appears greenish-yellow.