The outside red sandstone had been cleaned in 1988. But the interior blond stonework was now showing the effects of 100 years of accumulated dirt and grime.
Giffnock sandstone had been used in the interior of Kelvingrove. The staining was varied, and due to a variety of causes.
Traditional cleaning methods using steam and abrasion, as well as chemical and laser treatments, were tried on areas of the stonework. The results were poor, the processes laborious, and it was not proving to be cost effective.
Professor Norman Tennent, who was Head of Scientific Conservation from the late 1970s until 1987, was brought in to assist a team of consultants with trials.
A new method called Arte Mundit was tried. It had been used on St Paul’s Cathedral in London.
Arte Mundit involves using a chemical-infused latex being sprayed into the surface of the stonework. It is left for a period of time, them peeled off. The latex absorbs the dirt. When it is peeled off, the stonework is left clean and undamaged.
Some areas of staining were proving particularly difficult to clean. Professor Tennent worked with contractors and consultants to refine the mixture of latex and chemicals to deal with these areas.
This was the first time the Arte Mundit process had been used in Scotland, and the results are spectacular.
The project managers have left a small patch of these trials on the first floor eastern balcony so that visitors can see the transformation the stonework has undergone.