By Ellie Jones, Cathedral Archivist
There are hundreds of architectural records in the Cathedral Archives, including drawings, accounts, reports, photographs, and more. They record many aspects of the design and functionality of the Cathedral, from the whole edifice down to the tiniest details such as screws on handrails.
In the 21st century most architectural drawings are created using digital technology and specialist software. In the past, other solutions were needed to create and reproduce precision sections, plans, elevations and other technical drawings.
Blueprints are one of the most instantly recognisable formats. With their characteristic white lines on a blue background, blueprints are copies of original drawings made by ‘cyanotype’ contact printing. The technique was developed by Sir John Herschel in the 1840s and remained in common use for more than a century.
To create a blueprint a draftsperson first creates a drawing in black ink on translucent paper (historically this was often waxed or oiled paper or fine linen). The drawing is laid on top of a second sheet of paper coated with a light-sensitive solution (the most common being potassium ferrocyanide and ammonium iron citrate). Exposure to UV light causes a chemical reaction which turns any areas on the page not covered by inked lines blue. The blocked areas remain as white lines, resulting in a negative copy of the original drawing. This was an efficient method capable of producing multiple precise copies of a design before the advent of xerography and photocopying in the mid-20th century. Cyanotype is no longer used in architectural drawing, but it remains a popular form of alternative photography.
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‘Heritage Open Days: Introduction to the Cathedral’s Architectural Archives’ is taking place on Wednesday 17 September, 2pm-3pm. Attendance is free, but booking is essential. Click here to book your place.
For more information about Heritage Open Days events nationwide, click here