Glossary

Planar distortion — waving or rippling of the sheet, typically caused by uneven response to moisture. Whether cockling is stable at the object's current relative humidity is a conservation question, not a cosmetic one.

Discolouration caused by historic contact with water or by prolonged exposure to damp, often with a defined edge — a tideline — where the moisture stopped. It records an event in the sheet's history as well as being a condition issue.

Small brown or reddish spots in paper, associated with metallic impurities and fungal activity in the presence of moisture.

A brown discolouration in the shape of a window mat, caused by an acidic mount in prolonged contact with the sheet. Evidence of a sheet's framing history as well as damage.

Loss of the surface layer of the paper, usually caused by removing an adhesive, a backing or a hinge without adequate care.

Cut down from its original size. Trimming is irreversible and removes evidence: margins carry plate marks, inscriptions, dealers' codes and collectors' marks, and cutting them away narrows what can later be established about a sheet.

The ridge of metal raised alongside a drypoint line. Its presence, and how much of it survives, is evidence about where an impression sits in the printing sequence.

Lines scratched directly into the plate with a hard point, throwing up a ridge of displaced metal called burr. Burr holds ink and prints as a soft, velvety black — and it collapses under the press within a few dozen impressions, which makes it one of the most useful indicators of how early an impression is.

Source: Getty Art & Architecture Thesaurus, 300053228

An intaglio process. The plate is coated with an acid-resistant ground, the artist draws through the ground with a needle, and acid bites the exposed lines into the metal. The drawn line is free and fluent because the needle meets almost no resistance — quite unlike engraving.

Source: Getty Art & Architecture Thesaurus, 300053241

A single sheet printed from a plate. A print is not a unique object: one plate yields many impressions, and they can differ enormously from one another in inking, paper, wear and condition. This is why a census of impressions is worth building.

The impressed rectangle left in the paper by the edge of the plate under the pressure of the press. Its presence shows the sheet has not been trimmed inside the plate edge; its absence usually means it has.

The widely spaced lines in laid paper left by the mould's supporting wires. Their spacing is a property of the individual mould, so it can distinguish batches of paper that otherwise look identical — and unlike a watermark, chain lines run across the whole sheet, so trimming rarely removes them.

A smaller secondary mark, often initials, placed in the other half of the sheet from the main watermark. It can identify a particular mill or maker where the main mark is generic.

Paper made on a mould of closely spaced wires supported by widely spaced ones, leaving a visible grid when held to the light: fine laid lines and widely spaced chain lines. Standard for European paper of the seventeenth century.

Source: Getty Art & Architecture Thesaurus, 300014184

A design worked in wire into the papermaking mould, visible as a thinner, brighter area when the sheet is held to the light. Because papermakers' moulds were in use for limited periods, an identified watermark can narrow the years in which a sheet of paper — and therefore an impression printed on it — was made.

A systematic catalogue of all known works by an artist in a given medium, numbering each and describing its states. For Rembrandt's prints the current standard is the New Hollstein volumes; Bartsch's catalogue of 1797 and White & Boon's of 1969 remain in wide use, and they number and divide the works differently.

An impression printed after the artist's death, from a surviving plate. Rembrandt's plates were printed, reworked and reprinted for well over two centuries after 1669, so a large proportion of impressions in circulation are posthumous. This is a statement about when a sheet was printed, not about whether it is genuine.

The front and the back of a sheet. On a print the recto carries the image; the verso is where the ownership history is usually written, in collectors' stamps, dealers' codes and pencil annotations.

An impression pulled from an old plate in a later, usually commercial, edition. The Recueil Basan, published in Paris around 1810, is the best-known such edition of Rembrandt's plates.

A stage in the working life of a plate. Every time the plate is altered — lines added, passages burnished out, a signature redrawn — impressions printed after the change constitute a new state. States are defined by cataloguers, not by artists, and different catalogues divide the same plate differently.

A stamp or inscription applied to a print by an owner — private collectors and institutional print rooms alike. Marks are catalogued and numbered in Frits Lugt's standard reference, so a mark cited by its Lugt number identifies a specific collection, and thereby a documented point in a sheet's ownership history.

Source: Fondation Custodia / Marques de collections

The documented history of ownership and custody of an object. Gaps in it are normal and should be shown as gaps; a provenance narrated smoothly from creation to the present is usually a provenance with the uncertainty edited out.

A dated, itemised record of an object's physical condition at a point in time, written by a conservator. It is what makes it possible to tell later whether anything has changed — which is why one is made before an object travels and again when it arrives.

The standard document by which a borrowing institution describes its building, environment, security and staffing to a lender. In the United States the American Alliance of Museums' General Facility Report is the common form, and most lenders will not begin a serious conversation without one.

The unit of cumulative light exposure: illuminance in lux multiplied by hours of exposure. Light damage to paper and to media is cumulative and irreversible, so a lender who tracks lux hours can say what a sheet has already spent rather than guessing.

Source: Canadian Conservation Institute, Agents of Deterioration: Light

The board assembly a work on paper is housed in. A conservation-grade mount protects the sheet in handling and storage; an acidic one damages it over decades. An unmounted sheet is easier to examine and to photograph but less protected.

Light directed across the surface at a low angle, which reveals surface texture: cockling, creases, the impression of the plate mark, embossing, and the relief of heavily inked passages.

Photography with the light source behind the sheet rather than in front of it, so the paper's own structure — laid lines, chain lines, watermarks, thinning, repairs — becomes visible. It is the standard way to record a watermark, and it requires a conservator's judgement about handling.