Lightfastness – The ability of a printing ink to resist fading when exposed to light. This is different from the term ‘permanence’ in that it specifically refers to light, and more precisely to the quality of the pigment.
Color gamut – This is the range of colors that a printing ink can reproduce on a given substrate. Most offset printing is limited by the CMYK color gamut. However some printers will add additional spot colors that help them push the barrier of this color gamut. Hence their printing presses will be configured to print more than the four colors required for process color printing.
CMYK color gamut– Refers to cyan, magenta, yellow and black. This is the order that the inks are laid down on offset printing presses. The gamut refers to the ability of the first three colors to achieve a range of colors. This is a 3D model that can vary depending on the paper and ink quality.
Lakes – This term refers to pigments that have been mixed together by various means to give it desired properties. Pigments in nature are not always as pure, or have the properties desired by an ink manufacturer. Combining will sometimes accomplish this.
Toners – A term used by ink manufacturers to refer to a highly concentrated pigment that is used to alter the color strength of another ink.
Process colors – This refers to the combination of cyan, magenta, yellow and black. These colors together form the complete process for making full color images. Even though black is not considered a primary color, it is added to the process because it can take the place of cyan, magenta and yellow when they overlay one another.
Ink fountain – A part of the inking system in an offset printing press. It is the reservoir that holds the ink while it is being fed to the ink rollers.
Spot color – In four color process printing, this is a ink color that is added to the regular printing sequence. Printing presses that can run a spot color have 5 or more printing units. The first four are for the process colors, the remaining are for spot colors or varnishes. This is in order to push the boundaries of the color gamut. Or it’s purpose can be for the sake of a color sensitive part of the image, such as a logo. The advantage of a spot color is that there is no color variation throughout the print run. There is not need for the press operator to match the color with the regular process colors.
Pantone color – This is color matching system developed by the Pantone Color Institute. It is their branded system for having a uniform color matching system. The institute has clearly defined various shades of color and offset printers can communicate a defined standard with clients as to a desired color.
Blocking – This happens when a pile of sheets had been printed and the sheets stick to one another. Piles of sheets that are too high can create pressure on the lower sheets that have not completely dried. This causes the ink to stick to the ones underneath. The underlying problem is that the ink has not sufficiently dried and then the sheets form “blocks” that are stuck together.
Color sequence – This can vary between printing presses. Some will print process inks in the following order – cyan, magenta, yellow and black. This sequence gives more priority to the color as successive inline printing units will have inferior quality as the paper passes. Other printers will print in the following order – black, cyan, magenta, yellow. This order gives more priority to the quality of the black ink being printed. This is done mostly be printers who want to give more priority to a sharply printed type. Each order has it’s advantages. Almost always, any spot colors will print after the process colors.
Coverage – A term often used by printing press operators to refer to how much ink is covering a given sheet. It is expressed in a percentage.
Densitometer – This is a device that measures the density of an ink after it has been printed. The device does not see color, but instead can see how dark or light a printed spot is by means of a photoelectric eye. They measure how much light is absorbed and return a reading to the user.
Double bump – When printing process inks, this refers to an extra layer of ink overtop of a regular process color. For example, an offset printer might want to put a double layer of cyan on an image to increase the density range. The reason this would be necessary is that a printing unit is only able to lay down a thickness of 3.5 μm.
Fifth color – This is an additional spot color of ink printed immediately after the regular process colors of cyan, magenta, yellow and black. This can also be referred to as a spot color.
Ghosting – This more often than not refers to “mechanical ghosting”. This occurs when an ink is being laid down on the sheet of an offset press. It will sometimes produce a phantom image as the rollers go over the printing plate. This is caused by the ink being depleted from other areas of the plate
Hickey – This is a printing defect that is caused by a particle that is stuck to the offset printing plate or blanket. This particle will not allow the ink to transfer properly to the substrate. The hickey itself can come from the paper, dried ink skin, or any other foreign source.
Lithography – This is the term that describes the type of printing used by offset printing presses. It means that the method of printing is with water and ink together on a single printing plate.
Offset – This is refers to the method of applying the ink from the printing plate to the blanket. A printing plate will transfer the ink to the rubber blanket which will then roll on to the paper or other substrate. The reason that this offset takes place is because of numerous advantages, namely that the rubber blanket does not transfer the water, the blanket allows varying thicknesses of paper and the rubber does not wear the plate unlike the paper would.
Soy inks – These refer to ink that have soy bean oil as it’s vehicle base. This base has become very popular and even improved on petroleum based inks. Newspaper are the biggest users of soy ink due to it’s low rub-off quality.
Trapping – This is the ability of one ink to stick to another. In four color process printing, the first ink must be the tackiest. This is so that it can pull, or trap, the successive colors off of the printing blanket and onto itself. This is an important property in offset printing as the inks are still quite wet when laid down on the substrate. Only their tackiness will will properly track other inks.
Undercolor removal (UCR) – This is a means of reducing the amount of printing ink used in color printing. Cyan, magenta and yellow will theoretically produce black or gray. Printing black or gray instead only requires one layer of ink. Therefore designers will remove the undercolor process colors and just print black. This helps creates create sharper images and reduces ink consumption.
VOC – In this context, it refers to any chemicals in offset printing ink that have a low boiling point. The vapors produced can be toxic. Therefore ink manufacturers are very regulated by governments in the compounds that they are allowed to put in their printing inks.
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