On sheet XVI/16, Plan Villa Gazzotti at Bertesina, shown above, a red line has clearly migrated from the support mount into the drawing. As a result the paper now has an overall pink discolouration; this is irreversible. The ink line itself is not removed as it is part of the drawing's history. Similar discolouration has occurred to sheet XVI/9.
Conservation condition: Venice housing project, sheet XVI/9
Venice housing project, sheet XVI/9
Date of the drawing: circa 1550
Laid lines: 36mm apart
Watermarks: star, shield and letter M in the centre
Weight of paper: light, thin
Conservation condition of the drawing: fair; embedded creases, heavy cockling, adhesive residue and discolouration
The secondary support
The red ink line applied in the 18th century by Lord Burlington was either drawn around the mount or directly applied to the edge of the drawing. Fifty drawings in the RIBA Palladio collection have this type of border. Many of the drawings have been cropped so often the line is now only partially present.
Collectors would use these lines or elaborate mounts to indicate ownership, protect their collection and enhance their value; at the time it was aesthetically fashionable.
A gold line has been drawn around the edge of SB29/1 Plan of the Villa Guilia, shown above, applied by John Talman. This is on display at the Palladio 500 exhibition. This has also been partially cropped.
The reasons for mounts or support paper removal by the conservator are:
treatment is impossible without secondary support removal
poor attachment, degradation of adhesives
drawings were not presented to show the front and back image
poor quality, acidic, brittle
exhibition display requirements