Windowed Security Thread
Definition
A polymer strip embedded in the substrate that alternates between being below the surface (visible as a dark stripe in transmitted light) and emerging through windows (visible as a metallic segmented band in reflected light).
- Material
- Polymer strip embedded in the substrate
- Under transmitted light
- Continuous dark stripe
- Under reflected light
- Metallic segmented band at windows
- Common use
- Banknote security feature
Common questions
How does an examiner tell a genuine windowed thread from a printed or applied imitation?+
A genuine thread is woven into the paper during manufacture, so it alternates visibly between passing beneath the surface and emerging at windows, and it shows continuity and registration with the note's design; a printed imitation typically lies flat on the surface and lacks this true embedding.
Why do genuine notes show different appearances under transmitted versus reflected light?+
The thread's segments that lie beneath the paper surface block transmitted light evenly, appearing as a dark line when held to a light source, while the segments exposed at the surface windows reflect light off their metallic coating, so the two viewing conditions reveal different visual effects from the same physical feature.
Related terms
- BOPP (Biaxially Oriented Polypropylene)
- The polymer film substrate for polymer-substrate banknotes (Australia, New Zealand, UK, Canada). Distinguished from cotton-linen paper notes by FTIR-ATR (CH3 methyl peaks...
- Cotton-Linen Substrate
- The traditional banknote paper substrate made from cotton fibre (and sometimes linen), containing no lignin, non-fluorescent under UV, textured under magnification; used...
- Intaglio Printing
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- KINEGRAM
- A diffractive optically variable image device (DOVID) in holographic foil used on passport biographical pages and visa stickers; produced by OVD Kinegram...
- Latent Image
- A feature visible only at oblique viewing angle, produced by differential intaglio surface profile; on the US $100, tilting reveals 'USA' within...
- Microprinting / Microtext
- Text printed at 0.2-0.5 mm letter height, legible under a 10x loupe on genuine notes but smeared into an indistinct grey line...
- Multi-Tone Watermark
- A watermark produced by graded modulation of substrate thickness during papermaking, creating a range of light-to-dark tones visible in transmitted light; more...
- Optically Variable Ink (OVI)
- An ink containing thin-film interference flakes (metal + dielectric layers, manufactured by SICPA and others) that produce a visible colour shift with...
- See-Through Register
- The precise front-to-back alignment of partial printed elements so that they combine into a complete image when the note is held to...