Cockling
Definition
The wavy planar distortion of a paper sheet caused by differential shrinkage between areas that dried at different rates, typically visible as an undulating surface pattern in documents that have been wetted and then air-dried without weight or humidity control.
- Cause
- Differential drying shrinkage across a wetted sheet
- Appearance
- Wavy, undulating paper surface
- Common trigger
- Air-drying without weight or humidity control
Common questions
How is cockling prevented or corrected during document restoration?+
Documents are dried flat under light, even weight or between blotters with controlled humidity so the sheet shrinks uniformly; existing cockling can sometimes be relaxed by re-humidifying the paper in a controlled chamber and then re-drying it under restraint.
Does cockling affect the readability or examinability of writing and ink?+
The distortion itself does not erase writing, but a badly cockled sheet can make photography, scanning, and instrumental examination harder because the surface is no longer flat, so examiners often flatten the document before detailed analysis where the paper condition allows it.
Related terms
- Controlled Air Drying
- Drying of a wet document flat on acid-free blotter at controlled temperature (18-20°C) and relative humidity (45-55%), separated from adjacent pages, with...
- Freeze-Drying (Vacuum Lyophilisation)
- A drying technique in which water is first frozen and then sublimed under reduced pressure (below 611 Pa), bypassing the liquid phase....
- HPMC (Hydroxypropyl Methylcellulose)
- A water-reversible cellulose ether polymer used in dilute aqueous solution as an ink fixative; applied by atomiser to wet document surfaces to...
- Ink-Fixative Pretreatment
- Application of a dilute reversible polymer solution (HPMC, Cellugel) to the surface of a still-wet document before drying, forming a gel film...
- Mould Remediation
- The physical removal of established mould colonies from a document surface, typically by soft-bristle brush under HEPA-filtered vacuum; carried out when mould...
- Multispectral Imaging
- Photography or remote sensing in multiple wavelength bands beyond the visible spectrum, including near-infrared and short-wave infrared. Drone-mounted multispectral cameras are used...
- Saponin Treatment
- Application of a dilute aqueous saponin solution (a plant-derived surfactant) to a bloodstained document surface to reduce visible haemoglobin staining without significantly...
- Sequential Examination Protocol
- A formally agreed, documented inter-discipline sequence for examining a document that carries both handwriting or text evidence and biological evidence; the sequence...
- Tideline
- A concentrated deposit of dissolved ink chromophores, sizing agents, and mineral salts left at the advancing edge of a receding water front...