Mylar (Polyester) Sleeve
Definition
A chemically inert, optically clear polyester film sleeve used to protect questioned documents during examination and archival storage without introducing chemical contaminants that could affect ink or paper analysis.
- Material
- Chemically inert, optically clear polyester film
- Purpose
- Protects questioned documents during examination and storage
- Key property
- Does not introduce chemical contaminants
- Distinguished from
- ESDA Mylar film, which is used to lift indented writing, not to store documents
Common questions
Why is chemical inertness important for a document storage sleeve?+
Plasticizers or acidic compounds in a lower-grade plastic can migrate into paper and ink over time, altering ink composition or paper pH in ways that could affect later chemical or spectroscopic analysis. An inert polyester sleeve avoids introducing any such artifact into evidence that may be re-examined years later.
Can a document be examined for indented writing while still inside the sleeve?+
Optical and some non-contact examinations can be done through a clear sleeve, but techniques that require direct contact, such as ESDA processing, need the document removed first since the sleeve itself would block the vacuum and charge transfer. Handling protocols specify when removal is required.
Does the sleeve protect against fingerprint or trace evidence loss?+
It reduces further handling contamination and physical damage such as creasing or tearing, but it does not itself preserve latent prints or trace evidence already on the document; those must be processed or documented before or in coordination with sleeving, per chain-of-custody protocol.
Related terms
- Acid-Free Packaging
- Paper folders or envelopes manufactured without acidic buffers, used for long-term storage of questioned documents to prevent acid-catalysed paper and ink degradation.
- Chain of Custody
- The documented chronological record of who collected, handled, transferred, and examined a piece of evidence. For digital evidence, chain of custody includes...
- ESDA (Electrostatic Detection Apparatus)
- A non-destructive technique for detecting indented impressions on paper caused by writing pressure. A physical ink signature on paper produces detectable ESDA...
- IR Luminescence
- Emission of near-infrared radiation by ink dye molecules when excited by visible light; different ink formulations luminesce at different intensities, allowing differentiation...
- IR Reflectance
- Imaging under near-infrared illumination (715-1000 nm) to differentiate inks by their IR absorption: carbon-based inks remain dark, many synthetic dye inks become...
- Oblique Illumination
- Lighting applied at a very low angle to the document surface (below 10 degrees from horizontal) to reveal topographic features: writing indentations,...
- Transmitted Illumination
- Lighting passed through the document from the back face to reveal paper-body features invisible from the surface: watermarks, security threads, and paper-thickness...
- UV Fluorescence Examination
- Examination under 365 nm or 254 nm ultraviolet light to reveal optical brightener fluorescence in paper, ink luminescence, and areas of altered...
- Video Spectral Comparator (VSC)
- A multispectral imaging instrument combining UV, visible, and near-infrared illumination with selectable emission filters and a calibrated digital camera; the primary bench...