PVA Spray
Definition
Polyvinyl-acetate solution sprayed in a fine mist to consolidate the surface of a charred sheet so it can be handled, mounted and photographed without crumbling.
- Chemical
- Polyvinyl acetate solution
- Application
- Applied as a fine mist
- Target material
- Charred documents
- Purpose
- Consolidates the surface for handling and photography
Common questions
Why does a charred document need consolidation before it can be examined?+
Carbonised paper is extremely brittle and crumbles under ordinary handling, so the PVA coating stabilises the fragile surface enough for the sheet to be lifted, mounted, and photographed without losing fragments or legible text.
Does spraying PVA interfere with later analysis of the document?+
Applied correctly as a thin surface consolidant it should not obscure indented writing or ink, though examiners typically photograph and document the charred sheet before treatment to preserve an untreated record as well.
Related terms
- Charred Document
- Paper that has been burned to the carbonised stage but not fully reduced to ash; the cellulose has pyrolysed and the sheet...
- ESDA
- Electrostatic Detection Apparatus; detects latent indentations in paper by charging the surface and cascading toner particles, revealing tracing stylus pressure and writing...
- Glycerin Chamber
- Sealed humidification chamber held at 60 to 80 percent relative humidity using glycerin-water solutions to restore flexibility to charred or brittle paper...
- Indentation
- Latent pressure impression left on a lower sheet of paper when writing on an upper sheet; depth depends on pen pressure, paper...
- Oblique Light
- Side lighting at a low angle (5 to 15 degrees from the paper plane) that throws indentation shadows. The simplest indented-writing technique,...
- Secondary Writing
- Term for indented impressions: writing recovered from a sheet beneath the original, also called secondary or transferred writing.
- Steganography
- Concealing one file inside another in a way that hides the existence of the hidden file. LSB image manipulation, JPEG DCT coefficient...
- Sympathetic Ink
- Older name for invisible ink; the writing develops (becomes 'sympathetic') only after a heat, chemical or UV stimulus is applied.
- VSC
- Video Spectral Comparator (Foster + Freeman VSC-8000 series). Workhorse QD instrument combining UV, visible and IR sources with IR-sensitive cameras for ink,...