Grey Chalk Project
Resurrection of a historic type of lime.
Manifest Design Workshop are delighted to work with the Society for the Protection of Ancient Buildings at their Old House Project in Boxley, Kent. Working closely with the Society, we have helped to source grey chalk from a working quarry very close to the site itself, and attended the Working Party to build our first full-scale field kiln.
The driving force behind this programme of work and research is the re-discovery of an old form of lime – feebly hydraulic lime – which fills an important gap between the soft pure limes and the modern naturally hydraulic limes (NHL). Contemporary NHLs can be many times harder than advertised: while such hardness and impermeability can be helpful in specialised circumstances, these are often too strong for weak historic masonry. It is here that feebly hydraulic lime comes into its own. However, no such lime is manufactured in Britain, despite vast reserves of suitable stone. We aim to revitalise the production of local lime in small field kilns, producing material which is eminently suitable for local repair work. This project forms part of our ongoing Local Materials Initiative.