The use of dolomitic lime in mortar samples from a 15th-century buttress of York Minster (York, UK)

This paper describes the results of a series of analyses carried out on mortar samples from a 15th-century buttress of York Minster (York, UK). The aim of these analyses was to investigate the materials and technologies used in the late Middle-Ages for the construction of one of the most important religious places in Northern England. The limited knowledge currently available on the past use of locally-sourced construction materials represent an important limitation to the design of the new conservation works, since the choice of appropriate compatible materials can only be achieved through a detailed knowledge of the materials and technology used in the past. To provide an initial insight on the construction materials and technologies used at York Minster in the late Middle-Ages, mortar samples from one of the buttresses under restoration were collected and analysed using a variety of techniques such as optical and electron microscopy, X-ray diffraction analysis and Fourier Transform Infrared spectroscopy. The results suggest that the binder in this mortar was produced using locally available dolomitic limestone. The quicklime produced, a mixed oxide of calcium and magnesium, was directly mixed with locally-sourced river sand in a ratio 1:2.5 using a technology currently known as ‘hot mixed’ lime.