# Works on Paper: Watermarks, Foxing and Light > The sheet is evidence before the image is. Chain lines, watermarks and mould-mates date an impression, and a lux budget decides how often anyone is allowed to see it. > The Study - 2026-08-02 > Canonical HTML: https://iconotheca.com/study/works-on-paper-watermarks-foxing-and-light/ ## Key points - Laid paper records the mould's wires as close laid lines and widely spaced chain lines; wove replaced them with woven mesh from Baskerville's 1757 Virgil onward. - A watermark dates the sheet, not the image, and Hinterding found legible watermarks in only about a third of more than 7,000 Rembrandt impressions. - Nineteenth-century wood-pulp paper destroys itself through lignin and acid sizing, so a 1450 rag sheet can be chemically healthier than an 1880 one. - At 50 lux a light-sensitive sheet still earns only about three months on show every five years, and the fading does not come back. ## The sheet is a record of the mould that made it ## Watermarks date the sheet, and mould-mates date the impression ## Nineteenth-century paper is a slow fire, and older paper often is not ## Foxing is not a diagnosis, and the treatments are not free ## Light is the one loss that cannot be treated On paper the support carries more admissible evidence than the image does. The chain lines identify the mould, the watermark dates the batch, the fibre and the sizing date the manufacture, and the pattern of foxing and fading records where the sheet has been kept and how often it has been looked at. All of that was laid down by processes indifferent to the market that would later argue about the drawing. It is also, unlike an attribution, measurable - and it should be measured before anyone spends money on the connoisseurship. ## Questions **Does a watermark prove when a drawing was made?** It dates the sheet, which sets an earliest bound for the image on it, and nothing more. Its real power comes from mould-mates, where several impressions on paper from the same mould are grouped and the latest dated plate among them fixes a date at or after which the batch was in use. That is how lifetime impressions are separated from posthumous ones. **Does laid paper mean a sheet is old?** No. Laid pattern has been produced on machine-made paper by dandy roll since 1826, and the roll displaces fibres so the pattern is visible in transmitted light as well as on the surface. The dating evidence lies in the finer characteristics, including whether antique-style rib shadows are present along the chain lines, and in the watermark and fibre analysis. **Should foxing be treated before sale?** That is a conservation decision, not a cosmetic one. Every available route, from sodium borohydride to bleaches, peroxide and lasers, risks damaging the sheet, and the cause of foxing is not settled, so treatment is empirical. The disclosure question matters more commercially: prior chemical treatment should appear in the condition record, and frequently does not. **Why will a museum not lend a well-known drawing?** Because its light budget is spent. Standard practice caps light-sensitive works at 50 lux and restricts display to about three months in every five years, and exposure is cumulative and irreversible. A sheet that has been shown recently has no allowance left, regardless of the significance of the requesting exhibition. ## Sources - [1] Wikipedia, 'Laid paper': laid lines and chain lines, antique versus modern laid and the rib shadows, dominance in Europe from the twelfth to eighteenth centuries, dandy roll imitation. Tertiary source; replace with a standard paper-history reference. - [2] Wikipedia, 'Wove paper': James Whatman the elder (1702-1759), Baskerville's 1757 Virgil, Franklin's introduction to America and currency printing from about 1764, the paper machine of 1807, present share of production. Tertiary source. - [3] Wikipedia, 'Watermark': origin at Fabriano in 1282, method of manufacture, dandy roll from 1826, use in dating documents and artworks. Tertiary source. - [4] C. Richard Johnson Jr., 'Decision Trees for Watermark Identification in Rembrandt's Etchings', Journal of Historians of Netherlandish Art 12.2 (2020): Hinterding's 7,000-plus impressions, 2,369 watermarked sheets, 680 marks in fifty-four types, mould-mate dating, chain-line pattern matching. - [5] National Gallery of Victoria, 'Rembrandt's watermarked papers at the NGV': beta-radiography, transmitted and raking light, 140 prints, fifty-eight watermarks in eighteen design groups, the 1680 mark linked to Basan's posthumous printings. - [6] Wikipedia, 'Foxing': competing fungal and metallic hypotheses, humidity, rarity in incunabula and the decline in paper quality, treatment options and their risks. Tertiary source; replace with the AIC Book and Paper Group literature review. - [7] Conservation Center for Art and Historic Artifacts, 'Light Exposure for Artifacts on Exhibition': 50 lux for sensitive collections, 150 and 300 lux tiers, UV limits of 0-10 and maximum 75 microwatts per lumen, the lux-hours formula, three months every five years. - [8] Wikipedia, 'Acid-free paper': lignin and alum-rosin sizing, acid hydrolysis and slow fire, pH at or above 7, two per cent alkaline reserve, Barrow's 1930s research, ANSI/NISO Z39.48-1984 and ISO 9706 (1994), rag versus wood pulp. Tertiary source.