Gelatine Tissue Lift
Definition
A technique in which a fine-gauge gelatine tissue sheet, slightly humidified, is applied to a charred surface to lift a fragile carbon layer intact for transport or imaging; the gelatine is water-soluble and reversible.
- Material
- Fine-gauge gelatine tissue sheet, humidified before use
- Purpose
- Lifts a fragile carbon layer intact from a charred surface
- Property
- Water-soluble and reversible
Common questions
Why is reversibility important when lifting a charred document layer?+
Because the carbonised writing surface is extremely fragile and often the only surviving evidence, a reversible technique lets the examiner separate the gelatine carrier from the lifted layer later without further damaging or permanently altering the original material, preserving options for further analysis.
What risk does humidification of the gelatine sheet introduce?+
Moisture applied to a brittle, carbonised document can cause further disintegration if not carefully controlled, so the humidity level and contact time are managed closely to achieve enough tack for the lift without softening or breaking the charred material itself.
Why not just photograph the charred document in place instead of lifting it?+
In situ photography is done first where possible, but a fragment that is too fragile to handle, transport, or image clearly in place may need to be stabilised through a lift so it survives transit to a laboratory for controlled imaging under conditions the field cannot provide.
Related terms
- Ashing
- The terminal stage of heat damage, above approximately 400 degrees Celsius, in which carbon oxidises to carbon dioxide and only inorganic mineral...
- Charring
- The stage of heat damage at approximately 200 to 400 degrees Celsius at which paper cellulose converts to amorphous carbon; the sheet...
- Consolidant
- A dilute polymer solution (Paraloid B-72, Klucel G, Cellugel) misted over a fragile char surface to stabilise the carbon matrix before handling...
- Controlled Humidification
- Exposure of a charred document to 85 to 90 per cent relative humidity inside a sealed chamber, temporarily restoring pliability to the...
- 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...
- NIR Reflectance Imaging
- Photography of a document surface using illumination and camera detection in the near-infrared band (700 to 1100 nm), which differentiates carbon-based ink...
- Oblique-Light Photography
- Photography of a document surface using illumination at a low angle (10 to 15 degrees from the paper plane), which casts shadows...
- Principal Component Analysis (PCA)
- A multivariate statistical method used in fire debris research to reduce chromatographic data matrices to principal components that capture major variance. Used...
- Pyrolysis
- The thermal decomposition of cellulose in paper at approximately 150 to 300 degrees Celsius, disrupting glycosidic bonds and releasing water and carbon...