HPMC (Hydroxypropyl Methylcellulose)
Definition
A water-reversible cellulose ether polymer used in dilute aqueous solution as an ink fixative; applied by atomiser to wet document surfaces to prevent ink migration during drying. Also used as a reversible consolidant in conservation practice.
- Type
- Water-reversible cellulose ether polymer
- Forensic use
- Ink fixative on wet document surfaces
- Application method
- Atomiser, applied before drying
- Other use
- Reversible consolidant in conservation practice
Common questions
Why does an ink fixative need to be reversible?+
Forensic and conservation treatments must not permanently alter the original document, so a reversible fixative can later be removed or its effects undone if further testing or a different treatment approach becomes necessary, preserving the option for future examination.
At what stage of document recovery is HPMC applied?+
It is applied while the document is still wet, before drying begins, because its purpose is to hold ink components in place and prevent them migrating or feathering across the page as moisture moves during the drying process.
Does HPMC application affect later chemical testing of the ink?+
Because it is a water-reversible coating rather than a permanent chemical bond, properly applied HPMC is not intended to interfere with subsequent solvent-based ink analysis, though examiners typically document its use as part of the treatment record.
Related terms
- Cockling
- The wavy planar distortion of a paper sheet caused by differential shrinkage between areas that dried at different rates, typically visible as...
- 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....
- 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...