Inkjet Printing
Definition
Non-impact printing that sprays liquid ink droplets onto paper. Two main technologies: thermal (HP, Canon, bubble-jet) and piezoelectric (Epson).
- Field
- Questioned document examination, printer identification
- Category
- Non-impact printing
- Technologies
- Thermal (HP, Canon) and piezoelectric (Epson)
- Medium
- Liquid ink droplets
Common questions
How does an examiner distinguish thermal from piezoelectric inkjet output?+
Thermal printers vaporise ink with a heating element to form the droplet, which can leave subtly different dot shapes and edge characteristics compared to piezoelectric heads, which use mechanical pressure. Microscopic examination of dot morphology helps differentiate the two.
Why is inkjet output examined differently from laser printed text?+
Inkjet ink sits on the paper surface as wet droplets that can feather or show a characteristic dot pattern, unlike toner-based laser printing, which fuses dry particles to the page, so the two require different microscopic and chemical approaches.
Related terms
- ESDA
- Electrostatic Detection Apparatus; detects latent indentations in paper by charging the surface and cascading toner particles, revealing tracing stylus pressure and writing...
- 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...
- MIC / Yellow Tracking Dots
- Machine Identification Code: faint yellow micro-dots printed by many colour laser printers and copiers on every page, encoding serial number and timestamp....
- 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...
- Photographic Reproduction
- Lab-side imaging of a questioned document using controlled lighting (oblique, transmitted, coaxial), filters and wavelengths from UV through visible to IR, to...
- Transmitted-Light Photography
- Light passed through the paper from behind to reveal watermarks, paper-fibre disturbance, security threads, erasures and chemical thinning.
- VSC-8000
- Video Spectral Comparator by Foster + Freeman, the standard QD instrument in CFSL and GEQD labs, with broadband visible, UV (254, 365...
- Xerography
- Dry electrophotographic process invented by Chester Carlson (1938). Photoconductive drum is charged, exposed to image, dusted with toner, transferred to paper and...