Category Chemistry

Some printed images use one solid colour. These words are printed in solid black ink, for example. The dots are so close together that no background colour shows through. Using increasingly widely spaced dots creates the impression of paler tones of grey.

The color model (process color, four color) is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four ink plates used in some color printing: Cyan, Magenta, Yellow, and Key (black).

The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks “subtract” the colors red, green and blue from white light. White light minus red leaves cyan, white light minus green leaves magenta, and white light minus blue leaves yellow.

In additive color models, such as RGB, white is the “additive” combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta, and yellow.

With CMYK printing, half-toning (also called screening) allows for less than full saturation of the primary colors; tiny dots of each primary color are printed in a pattern small enough that humans perceive a solid color. Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots on the large white paper as lighter as and less saturated than the color of pure magenta ink.

Without half-toning, the three primary process colors could be printed only as solid blocks of color, and therefore could produce only seven colors: the three primaries themselves, plus three secondary colors produced by layering two of the primaries: cyan and yellow produce green, cyan and magenta produce blue, yellow and magenta produce red (these subtractive secondary colors correspond roughly to the additive primary colors), plus layering all three of them resulting in black. With half-toning, a full continuous range of colors can be produced.

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However colourful a page in a book may be, it is probably made up of only four colours. Tiny dots of yellow, blue, red and black inks are used to print the page. The dots are so small that they cannot usually be seen with the naked eye. Instead, they “mix” visually to form all the colours on the final page.

4-Color Process is the most widely used method for printing full-color images. All commercial printers use the 4-Color Process method for projects that contain multi-colored designs or photographs. This includes books, catalogs, manuals, magazines, brochures, postcards and any other printed items that contain full color images. Because of its widespread use in both offset and digital printing, 4-Color Process is much more affordable today than in years past.

As its name implies, 4 ink colors are used in 4-Color Process printing. These four colors are Cyan, Magenta, Yellow, and Black…which are known collectively as CMYK. In fact, 4-Color Process printing is frequently referred to as CMYK printing. It is also known as Four Color Printing, 4CP, Full Color Printing, or simply Process Printing.

Full-color images are created on the printing press by applying separate layers of the Cyan, Magenta, Yellow and Black inks. Thousands of colors can be reproduced by overlapping these CMYK colors in various concentrations. Applied as tiny dots on the paper (or other substrate), the four CMYK colors combine to create the visual effect we know as full color printing. Look at the photographs in a printed magazine or brochure under strong magnification and you will see the distinct CMYK dots.

No. Sometimes there are certain colors that cannot be reproduced exactly using the 4-Color Process method. In this case, PMS colors (also known as Spot colors or Pantone Matching System colors) are used to create a particular color. PMS colors are specific color formulas that will reproduce accurately in print. Instead of simulating colors by layering multiple ink colors with the CMYK 4-Color Process, PMS ink colors are pre-mixed from existing color formulas and assigned a standardized number.

PMS colors are often used in conjunction with the four CMYK process colors on certain projects. These are referred to as 5-color or 6-color projects because they use the four CMYK colors plus one or two PMS colors (or more) for certain elements of the design, such as a corporate logo. PMS colors generally involve an upcharge, so they are usually reserved for projects that require a specific color (or colors) that cannot be reproduced accurately by layering the four CMYK colors.

Only a small percentage of full-color projects necessitate the addition of PMS colors because most graphic designers refer to a Pantone Process Book and then use the process color formula that is closest to the desired PMS Spot color. So if you intend to print the entire piece using CMYK 4-color process, it is important that you don’t designate PMS Spot colors in your artwork design. Otherwise when your PMS Spot color is converted to a CMYK process color to create printed output, it could yield a result you weren’t anticipating. If in doubt, always consult with your printer before getting too deep into your project.

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Printing—producing identical copies of a picture or piece of writing by pressing an inked block onto a surface — was introduced by the Chinese over a thousand years ago. However, the breakthrough of movable type, which meant that a new block could be made up from existing pieces of type, without having to carve it from scratch, was developed in 1438 by Johannes Gutenberg, in Germany. This was still a fairly slow, manual method, although much faster than the alternative of writing documents out by hand. It was not until the invention of steam and, later, electrical machinery to power the presses that documents could be printed rapidly on a large scale.

Nearly 600 years before Gutenberg, Chinese monks were setting ink to paper using a method known as block printing, in which wooden blocks are coated with ink and pressed to sheets of paper. One of the earliest surviving books printed in this fashion — an ancient Buddhist text known as “The Diamond Sutra” — was created in 868 during the Tang (T’ang) Dynasty (618-909) in China. The book, which was sealed inside a cave near the city of Dunhuang, China, for nearly a thousand years before its discovery in 1900, is now housed in the British Library in London.

The carved wooden blocks used for this early method of printing were also used in Japan and Korea as early as the eighth century. Private printers in these places used both wood and metal blocks to produce Buddhist and Taoist treatises and histories in the centuries before movable type was invented.

An important advancement to woodblock printing came in the early eleventh century, when a Chinese peasant named Bi Sheng (Pi Sheng) developed the world’s first movable type. Though Sheng himself was a commoner and didn’t leave much of a historical trail, his ingenious method of printing, which involved the production of hundreds of individual characters, was well-documented by his contemporary, a scholar and scientist named Shen Kuo.

But all that changed in the middle of the 15th century, when Johannes Gutenberg established himself as a goldsmith and craftsman in Strasbourg, Germany.

Like Bi Sheng, Wang Chen and Baegun before him, Gutenberg determined that to speed up the printing process, he would need to break the conventional wooden blocks down into their individual components — lower- and upper-case letters, punctuation marks, etc. He cast these movable blocks of letters and symbols out of various metals, including lead, antimony and tin. He also created his own ink using linseed oil and soot — a development that represented a major improvement over the water-based inks used in China.

But what really set Gutenberg apart from his predecessors in Asia was his development of a press that mechanized the transfer of ink from movable type to paper. Adapting the screw mechanisms found in wine presses, papermakers’ presses and linen presses, Gutenberg developed a press perfectly suited for printing. The first printing press allowed for an assembly line-style production process that was much more efficient than pressing paper to ink by hand. For the first time in history, books could be mass-produced — and at a fraction of the cost of conventional printing methods.

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