Session 4: Mortar, Stone, Stucco, Scagliola

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Francesca Gherardi began Session 4 with her talk “Application of Nanolimes for the Consolidation of Limestone from the Medieval Bishop's Palace, Lincoln, UK”. Her research evaluated three different nanolime consolidants for the treatment of deteriorating limestone. Her approach, which included both laboratory and in-situ trials, highlights the importance of rigorous material testing and continued evaluation when considering novel conservation materials. Of the three nanolime consolidants tested, there appeared to be one clear winner, leaving us eager to hear more from Francesca as she continues monitoring these products in-situ. 

Martin Michette’s presentation “Assessing the Long-term Success of Reigate Stone Conservation Strategies at Hampton Court Palace and the Tower of London”, evaluated the efficacy of various conservation treatments applied to Reigate stoneworks at the aforementioned locations.  Reigate stones believed to have undergone wax treatment, limewashing, or HCT were investigated to inform on-going conservation strategies. Martin asserted the need for well documented long-term testing strategies to develop appropriate conservation methods for Reigate and other stones.

Katharina Fuchs’ presentation “Scagliola Interiors in Vienna, 1800–1900: Material, Development and Conservation,” discussed the significant differences in scagliola production and the complications arising with treating something that has no standard method of treatment. With a comparison of common deterioration factors and current methods of treatment she discussed how the future of scagliola treatment is linked to the past with the traditional knowledge of the craftsmen.

Q&A: Ethics, and the loss of traditional craft skills and materials

Throughout the Q&A, our panelists were asked about the conservation ethics of maintaining traditional materials on the related stoneworks. As posed in Katharina Fuchs’ presentation the number of scagliola craftsmen with traditional knowledge is shrinking, which will be a devastating loss to conservation as their involvement to current treatments is heavily relied upon. Knowledge sharing beyond borders has become crucial to the maintenance of scagliola.

Loss of traditional materials also posed an issue within Martin Michette’s discussion as the mining of Reigate stone has ceased. He added that its replacement with continually harder limestones has not been as suited as repairs become more obvious and further from the traditional methods. Martin also sought to address the subject of allowing buildings to age gracefully noting that some aspects of traditional maintenance can be a part of the intangible built heritage. Martin commented that “[some] ceremonies link material, environment and culture in a way which makes the building more than a sum of its parts. [For example,] the White Tower got its name from the frequent limewashing of its walls, ([which were likely] largely Reigate stone back then). … There can be a cultural component to the care of historic architecture.”

Our panelists discussed how their projects look to the future of conservation to respect the integrity of historic buildings. Francesca touched upon the need for sustainability and durability when considering innovative materials for treatment. She also emphasized the importance of obtaining information from both a lab and in-situ setting as the varying results for durability and application can drastically affect the treatment.

Session 4 was a gripping discussion of how to respectfully maintain the traditions of the past as we strive to preserve them for years to come.


Jessica Bekesi is an Objects Conservator from Northwestern Ontario.

Kasey Hamilton is a recent graduate of the UCLA/Getty Interdepartmental Program (2020) in the Conservation of Archaeological and Ethnographic Materials.

Tatiana Shannon, Pre-Program Conservation Technician