The gypsum plaster floor extends over the whole upper floor of the southern arm of the Minster’s vestibule and may originally have been even larger. Master masons inscribed the plaster floors with the shapes of windows, the curves of vaults and other details of their buildings. From these tracings, templates were made enabling the masons to cut their stonework precisely as the master mason intended. The templates were cut out of thin wooden boards, and or thin sheets of metal. Numbers of wooden, iron and zinc templates still hang in bundles from the attic walls of York Minster cathedral.

A plaster floor was expedient because a mere brushing over would obscure earlier drawings, while the freshly scratched lines would show white and sharp. This meant that the surface of the floor in the course of time came to be layered with patterns of straight and curving lines, which had no connection with one another. The 3D laser scanning process allows the various layers to be visually peeled and seen separately but in context. The tracing floor “is an amazing and little-known treasure of York Minster, hidden away above the vault of the Chapter House passage and normally quite inaccessible,” said Dr Peter Addyman, former director of the York Archaeological Trust. 3D laser scanning “allows us to get sub-millimeter accuracy in the recording of lines”. Preliminary analysis of the drawings, indicate they are of the Gothic Perpendicular style (1350-1539).

In an era when few people could read or write, even fewer people, craftsmen included could understand a drawing done to scale. That is: a drawing of a building and its parts drawn at a size that was less than its actual size. The scale drawing was as much an abstraction as the printed word. The most direct way to overcome this handicap was merely and directly to draw the building’s parts at their actual size on the floor in plaster and trace them onto templates from which the workers could cut their stone. In today’s architectural parlance “Tracery” refers to the curved intersecting muntins in the upper parts of a window. (Pevsner et al “the Penguin Dictionary of Arch” 1966).

Sources:

- Vicky Sypsa, University of York UK.
- Aylmer, G. F. & R. Cant (1977) 'A History of York Minster'. Clarendon Press.

- Coldstream, N. (1972) 'York Chapter House', in Journal of the British Archaeological Association, Third Series 35, p.15-23.

- Giles, K. F. (2002) in The Friends of York Minster Annual Report 73, p. 21-29.

- Giles, K. F. (2001) in The Friends of York Minster Annual Report 72, 25-28.

- Harvey, J. H. (1968) 'The Tracing Floor in York Minster' in The Friends of York Minster Annual Report 40, p.9-13.

- Hughes, J. Q. (1955) 'The Timber Roofs of York Minster' in Yorkshire Archaeological Journal 38(1952-55), p.475-494.

- Melmore, S. (1969) 'York Minster-Notes on the construction of the Chapter House and its vestibule', in Yorkshire Archaeological Journal 42 (1967-70), p.345-348.

- Norton, C. (1999) 'The Anglo-Saxon Cathedral at York and the Topography of the Anglian City', in Journal of the British Archaeological Association 151: 1-42, p.14-15.

- Wander, S. H. (1978) 'The York Chapter House',in GESTA 17(2), p.41-49.