Glossary of inkjet terms

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.

ActuatorThe 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
AdditiveA material added to an ink in small concentrations used to modify its properties
AddressabilityThe number of individually addressable points in a given area of print, usually expressed in DPIxDPI
AgglomerationJoining 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 lampA 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 inkjetA form of continuous inkjet technology where the drops are either printed or recirculated
Bubble inkjetA 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)
CappingCovering the printhead when not in use to protect from damage, solvent evaporation and UV light
CarrierThe majority component of an ink, into which the other components are dissolved or dispersed
CIJContinuous Inkjet, one of the two broad types of inkjet technology, the other being drop on demand (DOD), or impulse inkjet
CMYKCyan, 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 gamutThe range of colours that can be reproduced with a process colour ink set
Colour profilingA method of ensuring correct colours are reproduced in the print when referenced to the source image
ColorantThe material (dye or pigment) used to give colour to the print, due to selective absorption or reflection of different wavelengths of light
Continuous inkjetOne of the two broad types of inkjet technology, the other being drop on demand (DOD), or impulse inkjet
cPCentipoise, the unit of viscosity, equal to 1 mPa s in SI units
CPIChannels 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
CuringUsing 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)
DegassingRemoval 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)
DODDrop-On-Demand, one of the two broad classes of inkjet technology, the other being continuous inkjet (CIJ)
Dot gainThe 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 sizeThe diameter of a printed dot on the substrate
DPIDots Per Inch, a measure of the addressability (although often referred to as 'resolution') of an inkjet printer
Drive electronicsThe 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 waveformThe electrical signal applied to the printhead actuator or heater to eject ink from the ink chamber
Drop placement accuracyThe 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 volumeThe volume, in pL (picolitres) of the drop ejected from the printhead
Drop velocityThe speed at which the drop is ejected from the printhead
Dwell timeSee latency time
DyeA colorant that is soluble in the ink carrier
Edge/end shooterA 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 shooterPrinthead where the actuator diaphragm or heater is parallel to the nozzle plate
FastnessThe resistance to degradation of a printed image by water (water-fastness), washing (wash-fastness), abrasion (rub-fastness) and UV light (light-fastness)
Firing frequencyThe number of drops ejected from a nozzle per second
Fixed array (or single pass) printingA 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
FlocculationJoining 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
FoamingFormation of air bubbles in the ink when agitated, caused by dissolved gas coming out of solution
Functional fluidAn 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)
HeaterIn 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 profileA set of data that characterises a colour input or output device, or a colour space, according to International Color Consortium standards
Image qualityA qualitative, subjective assessment of the printed image (as opposed to print quality)
InkA fluid containing a carrier, a colorant or other functional material, and potentially other additives
Ink chamberThe 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
InterlacingBuilding 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
KogationDeposition 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)
LigamentA 'tail' of additional ink that follows the main drop once it has formed after ejection from the nozzle
MeniscusThe 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 inkjetA form of continuous inkjet where drops can be deflected to multiple positions on the substrate
NozzleThe small opening in the ink chamber from which the ink is ejected
Nozzle densityThe spacing between nozzles in a printhead, normally given in nozzles per inch (NPI)
Nozzle plateThe flat surface constructed from metal, polymer or silicon, into which the nozzles are formed
NPINozzles Per Inch, a measurement of nozzle density
ODOptical density (or absorbance) - a measure of how strongly an ink absorbs light
OEMOriginal Equipment Manufacturer, a company that makes a product but sells it via someone else, normally without the manufacturing company's name being attached
Open timeSee decap time
Phase changeA 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)
PigmentA colorant that is insoluble in the carrier, forming discrete particles as a dispersion
PinningUse of a small UV lamp to partially cure a UV cure ink and fix the drops in place, prior to full curing
PistonAn actuator configuration where the piezo material is expanded and contracted along its length, resulting in a displacement in the same direction
pLPicolitre, or 1 million millionth of a litre (10-12 L)
POPPoint Of Purchase, the place where goods are sold, used to refer to graphical advertising
POSPoint Of Sale, the place where goods are sold, used to refer to graphical advertising (also known as POP or point of purchase)
ppmPages Per Minute, the output speed of a printer, normally for A4 or US letter-sized sheets
ppmParts Per Million, concentration of a minor component in a solution
PQPrint Quality
Print qualityA quantitative, objective measure of dot and line characteristics and other factors in the printed image (as opposed to image quality)
PrintheadComponent of the inkjet system containing an array of nozzles able to eject small drops of ink
Print-to-cure timeThe time between the drop landing on the surface and it being fully cured
Process colourA 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
PZTLead zirconium titanate, the main piezoelectric material used in printheads
RecirculatingPrintheads (and the ink systems that supply them) allowing ink to be circulated continuously past the nozzles
ResolutionThe 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 modeAn actuator configuration where the piezo material deflects a diaphragm in the roof of the ink chamber which is perpendicular to the nozzle plate
SatelliteAn 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
ScanningPrinting 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 rateThe rate of change of flow velocity with distance in a fluid
Single passSee fixed array
SOHOSmall Office, Home Office market, which for printers implies small directly connected, rather than networked printers
Solid inkPhase change ink
SolventAn organic liquid (or water) used as the carrier in a solvent ink, into which the other components are dissolved
SpittingEjecting ink from the nozzles when not being used for printing, to maintain fresh ink at the nozzle
Spot colourColours are produced using specific coloured inks, rather than from combining coloured dots
StitchingThe joining of print swathes to give a continuous image
Substrate (or media)The material or materials being printed on
Surface tensionSurface 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 distanceThe distance between the printhead and the substrate, or the distance travelled by an ink drop
TIJThermal Inkjet, see above
TiO2Titanium dioxide, a commonly used white pigment
Tube modeA tubular piezo element surrounding an ink chamber where squeezing the tube creates the necessary pressure wave to eject a drop
UVUltraviolet (radiation)
UV cureA 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
ViscoelasticityThe property of materials that exhibit both viscous and elastic characteristics when undergoing deformation
ViscosityMeasure of the resistance of a fluid to shear or tensile stress (flow)
VOCVolatile 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
WettingThe spreading of ink on a substrate determined by the ink surface tension and the substrate surface energy
WipingRemoval of excess ink and dirt from the printhead nozzle plate