Confused about the meaning of some inkjet technical terms? Can't remember the difference between kogation and agglomeration? Or dwell versus decap? Our glossary of inkjet terms should help.
| Actuator | The part of the printhead that causes the ink ejection from the nozzle, usually a piezoelectric element (this role is played by the heater in a TIJ printhead |
| Additive | A material added to an ink in small concentrations used to modify its properties |
| Addressability | The number of individually addressable points in a given area of print, usually expressed in DPIxDPI |
| Agglomeration | Joining together of pigment particles to make larger particles, which causes problems in a dispersion |
| Aqueous (or water-based) | An ink using water as the carrier |
| Arc lamp | A UV light source using an excited mercury vapour to emit ultraviolet light |
| Binary (or binary printhead) | A drop-on-demand printhead where all drops ejected by the printhead are of the same volume (as opposed to a greyscale printhead) |
| Binary continuous inkjet | A form of continuous inkjet technology where the drops are either printed or recirculated |
| Bubble inkjet | A drop on demand technology where the ink is boiled very rapidly to grow a bubble and eject a drop. Also known as Thermal Inkjet (TIJ) |
| Capping | Covering the printhead when not in use to protect from damage, solvent evaporation and UV light |
| Carrier | The majority component of an ink, into which the other components are dissolved or dispersed |
| CIJ | Continuous Inkjet, one of the two broad types of inkjet technology, the other being drop on demand (DOD), or impulse inkjet |
| CMYK | Cyan, magenta, yellow and black (black is referred to as K because it is the 'key' colour used for registering other colours in traditional printing, and also avoids confusion with blue in RGB) process colours used to form full colour images. If a separate black ink is not used, then the black formed using just the three colours is referred to as a composite black |
| Colour gamut | The range of colours that can be reproduced with a process colour ink set |
| Colour profiling | A method of ensuring correct colours are reproduced in the print when referenced to the source image |
| Colorant | The material (dye or pigment) used to give colour to the print, due to selective absorption or reflection of different wavelengths of light |
| Continuous inkjet | One of the two broad types of inkjet technology, the other being drop on demand (DOD), or impulse inkjet |
| cP | Centipoise, the unit of viscosity, equal to 1 mPa s in SI units |
| CPI | Channels Per Inch, equivalent to nozzle density (NPI) |
| Curie temperature (or point) | The temperature above which the piezoelectric behaviour of a piezoelectric material is completely lost |
| Curing | Using either heat or UV light to cause a polymerisation reaction in a suitable ink, causing it to become solide |
| Decap time (or open time) | The time that nozzles can be uncovered and idle before they will no longer print (and need to be recovered by purging) |
| Degassing | Removal of dissolved air from the ink to avoid bubbles forming in the printheads, which otherwise can cause nozzle failures |
| Dispersion | (n.) a two-phase mixture of incompatible materials, for example small particles suspended in a liquid. (v.) the act of creating such a suspension |
| Dithering (spatial dithering) | The representation of a grey level using a pattern of dots which, from a distance, gives an appearance equivalent to the average coverage of the dots (also known as screening or halftoning) |
| DOD | Drop-On-Demand, one of the two broad classes of inkjet technology, the other being continuous inkjet (CIJ) |
| Dot gain | The size of a dot due to the wetting of the ink on the substrate, relative to the size of the drop if no spreading had occurred |
| Dot size | The diameter of a printed dot on the substrate |
| DPI | Dots Per Inch, a measure of the addressability (although often referred to as 'resolution') of an inkjet printer |
| Drive electronics | The hardware interface between the main computer controlling the system and the printheads |
| Drive voltage (or offset voltage) | The key characteristic voltage amplitude of the printhead drive waveform |
| Drive waveform | The electrical signal applied to the printhead actuator or heater to eject ink from the ink chamber |
| Drop placement accuracy | The accuracy with which drops can be landed onto the substrate, dependent on jet straightness, throw distance and consistency of the drop velocity |
| Drop size, drop volume | The volume, in pL (picolitres) of the drop ejected from the printhead |
| Drop velocity | The speed at which the drop is ejected from the printhead |
| Dwell time | See latency time |
| Dye | A colorant that is soluble in the ink carrier |
| Edge/end shooter | A drop on demand printhead where the drops are fired from nozzles on the edge of the printhead, perpendicular to the action of the heater or actuator. 'End shooter' is also used to distinguish conventional printheads from those with ink recirculation past the nozzles. |
| Face shooter | Printhead where the actuator diaphragm or heater is parallel to the nozzle plate |
| Fastness | The resistance to degradation of a printed image by water (water-fastness), washing (wash-fastness), abrasion (rub-fastness) and UV light (light-fastness) |
| Firing frequency | The number of drops ejected from a nozzle per second |
| Fixed array (or single pass) printing | A printing configuration where an array of printheads cover the whole width of the substrate to be printed, and the substrate passes under the printheads, giving high speed printing with no movement of the printheads |
| Flocculation | Joining together or coagulation of particles in a dispersion to form larger particles. Often taken to be synonymous with agglomeration but in the inkjet industry flocculation is generally taken to be a process reversible by shaking, whereas agglomeration is essentially irreversible, requiring milling and/or introduction of a dispersing agent. |
| Flush | (n.) A compatible fluid used for cleaning ink systems and printheads. (v.) Cleaning ink systems and printheads by passing a cleaning liquid (or flush) through the system |
| Foaming | Formation of air bubbles in the ink when agitated, caused by dissolved gas coming out of solution |
| Functional fluid | An ink used to deposit a material with a specific application function (e.g. electrical conductivity), rather than to print colour |
| Greyscale (or greyscale printhead) | A drop-on-demand printhead capable of ejecting drops of different sizes, used to provide improved print quality (as opposed to a binary printhead) |
| Heater | In a thermal inkjet printhead, the heater heats the ink to is boiling point, causing rapid expansion and increase in pressure, leadng to ejection of ink from the nozzle |
| ICC profile | A set of data that characterises a colour input or output device, or a colour space, according to International Color Consortium standards |
| Image quality | A qualitative, subjective assessment of the printed image (as opposed to print quality) |
| Ink | A fluid containing a carrier, a colorant or other functional material, and potentially other additives |
| Ink chamber | The part of the printhead behind each nozzle, from where the ink is ejected |
| Ink system (or ink supply system) | Responsible for delivering ink to the printhead at the required temperature and pressure |
| Interlacing | Building up an image in a scanning printer using multiple printing passes in a pattern designed to disguise the effect of missing nozzles |
| Jet straightness (or jet deviation) | The extent to which a drop is ejected perpendicular to the nozzle plate |
| Kogation | Deposition of decomposed ink onto the heater elements in thermal inkjet |
| Latency time (or dwell time) | The time that nozzles can be left uncovered and idle before there is a significant reduction in performance, for instance a reduction in drop velocity or drop volume that will noticeably affect the image quality |
| LED (or UV LED) | Light emitting diode, a compact solid state UV source with good efficiency and fast start (as opposed to an arc lamp) |
| Ligament | A 'tail' of additional ink that follows the main drop once it has formed after ejection from the nozzle |
| Meniscus | The interface between the ink and the outside air at the nozzle, curved because of the pressure difference between the ink and atmospheric pressure |
| Meniscus pressure (or vacuum) | The (negative) pressure difference between the ink in the printhead and atmospheric pressure |
| Moving wall (or shared wall) | A type of piezo printhead design where the walls surrounding the ink chambers are active and flex to create the necessary pressure wave for drop ejection |
| Multi-level continuous inkjet | A form of continuous inkjet where drops can be deflected to multiple positions on the substrate |
| Nozzle | The small opening in the ink chamber from which the ink is ejected |
| Nozzle density | The spacing between nozzles in a printhead, normally given in nozzles per inch (NPI) |
| Nozzle plate | The flat surface constructed from metal, polymer or silicon, into which the nozzles are formed |
| NPI | Nozzles Per Inch, a measurement of nozzle density |
| OD | Optical density (or absorbance) - a measure of how strongly an ink absorbs light |
| OEM | Original Equipment Manufacturer, a company that makes a product but sells it via someone else, normally without the manufacturing company's name being attached |
| Open time | See decap time |
| Phase change | A type of ink which is solid at room temperature. The ink is heated in the printhead so it becomes a liquid and can be ejected, and on contact with the substrate it freezes to a solid |
| Piezo (or piezoelectric) | A material exhibiting the piezoelectric effect, where mechanical distortion of the material results in the formation of a charge across the material, or vice versa. The most common material in general use is lead zirconium titanate (PZT) |
| Pigment | A colorant that is insoluble in the carrier, forming discrete particles as a dispersion |
| Pinning | Use of a small UV lamp to partially cure a UV cure ink and fix the drops in place, prior to full curing |
| Piston | An actuator configuration where the piezo material is expanded and contracted along its length, resulting in a displacement in the same direction |
| pL | Picolitre, or 1 million millionth of a litre (10-12 L) |
| POP | Point Of Purchase, the place where goods are sold, used to refer to graphical advertising |
| POS | Point Of Sale, the place where goods are sold, used to refer to graphical advertising (also known as POP or point of purchase) |
| ppm | Pages Per Minute, the output speed of a printer, normally for A4 or US letter-sized sheets |
| ppm | Parts Per Million, concentration of a minor component in a solution |
| PQ | Print Quality |
| Print quality | A quantitative, objective measure of dot and line characteristics and other factors in the printed image (as opposed to image quality) |
| Printhead | Component of the inkjet system containing an array of nozzles able to eject small drops of ink |
| Print-to-cure time | The time between the drop landing on the surface and it being fully cured |
| Process colour | A technique where a wide range of colours (the colour gamut) is reproduced by combining dots of CMYK or an alternative colour set |
| Purging (or priming) | Pumping ink through the printhead to remove air bubbles or dirt and recover inoperative nozzles |
| PZT | Lead zirconium titanate, the main piezoelectric material used in printheads |
| Recirculating | Printheads (and the ink systems that supply them) allowing ink to be circulated continuously past the nozzles |
| Resolution | The ability of a printer to reproduce fine detail. In common usage this is taken to be equivalent to addressability, but high addressability will only equate to high resolution if the dot size is small enough and the placement accuracy good enough |
| RIP (or RIP software) | Raster Image Processing software, which takes a continuous tone image file input and produces a colour profiled, screened, bitmap output to be sent to the drive electronics |
| Roof mode | An actuator configuration where the piezo material deflects a diaphragm in the roof of the ink chamber which is perpendicular to the nozzle plate |
| Satellite | An unwanted drop produced behind the main drop, which either merges with the main drop (fast satellite) or drifts away from the main drop (slow satellite) to land in a different place on the substrate |
| Scanning | Printing modes which involve printheads being moved over the substrate (and/or the substrate under the printheads) to print in a series of swathes |
| Screening (halftoning) | The representation of a grey level using a pattern of dots which, from a distance, gives an appearance equivalent to the average coverage of the dots (also known as spatial dithering) |
| Shear rate | The rate of change of flow velocity with distance in a fluid |
| Single pass | See fixed array |
| SOHO | Small Office, Home Office market, which for printers implies small directly connected, rather than networked printers |
| Solid ink | Phase change ink |
| Solvent | An organic liquid (or water) used as the carrier in a solvent ink, into which the other components are dissolved |
| Spitting | Ejecting ink from the nozzles when not being used for printing, to maintain fresh ink at the nozzle |
| Spot colour | Colours are produced using specific coloured inks, rather than from combining coloured dots |
| Stitching | The joining of print swathes to give a continuous image |
| Substrate (or media) | The material or materials being printed on |
| Surface tension | Surface force restraining a liquid, normally measured in dynes/cm2 (SI unit N m-1). Equivalently the amount of work required to create a unit of surface area |
| Swathe (or print swathe) | The strip of print produced by a single scan of a scanning system |
| Thermal inkjet (TIJ) | A drop-on-demand (DOD) technology where the ink is heated rapidly to grow a bubble and eject a drop. Also referred to as bubble inkjet |
| Throw distance | The distance between the printhead and the substrate, or the distance travelled by an ink drop |
| TIJ | Thermal Inkjet, see above |
| TiO2 | Titanium dioxide, a commonly used white pigment |
| Tube mode | A tubular piezo element surrounding an ink chamber where squeezing the tube creates the necessary pressure wave to eject a drop |
| UV | Ultraviolet (radiation) |
| UV cure | A process in which an ink undergoes a chemical reaction of polymerisation (and change of the state from liquid to solid) when exposed to UV radiation |
| Viscoelasticity | The property of materials that exhibit both viscous and elastic characteristics when undergoing deformation |
| Viscosity | Measure of the resistance of a fluid to shear or tensile stress (flow) |
| VOC | Volatile Organic Compound, part of an ink formulation that is volatile and potentially hazardous |
| Waveform (or drive waveform) | The electrical signal applied to the printhead actuator or heater to eject a drop of ink |
| Wetting | The spreading of ink on a substrate determined by the ink surface tension and the substrate surface energy |
| Wiping | Removal of excess ink and dirt from the printhead nozzle plate |