Print Colour

Paper Finish

A walkthrough of the need-to-knows of printing.

TCpublishing

RGB &CMYK

Forgetting to convert an image from RGB to CMYK could result in a poor look-ing print job, and being aware of the processes involved in print production can prevent this error. As well as a poten-tially irritated client.Note that whenconverting from screen to print, the colours will not always be exact, but rather matched to the nearest colour within therespective gamut.

RGB is mainly used for screen, such as web design, as the colour spectrum, or rather gamut is nowhere near as vast as the gamut for CMYK.

Full colour is attained by breaking down the original image into 4 components

which are the 4 basic print colours, cyan, magenta, yel-low and key (aka black)Black is added to give more definition and density to an area, which is essential to a full colour print job.

RGB are also known as “additive colours” because when all colours are com-bined they create white, which can only be viewed from a light transmitted source, for example the sun or a lamp.

When two of these colours overlap, we get what is known as “subtractive colours”, however when the combination of all these colours overlap, black is created, which is also known as registration black, as is used for registration marks.

Colour Seperation

halftone dots, traditional print methods, and tiny grids.

Traditionally, after seperating an image into the process colours, they would be prepared for silkscreen or what is known today as screen printing. In the days before imagesetters, platesetters, and scanners, seperation could only be done by photographic means.

This requires making a negative for each of the colours, but for each of the subtrac-tive colours, a filter of the respective addi-tive was used to print. This was to ensure that all wavelengths of light reflected from the corresponding colour was not recorded on the emulsion used in the photographic process.

When the plates have been made, it is imperitive that the rows of dots have to be put at the correct angle, else moire patters can occur. When printing in 4 colours, the following angles in degrees are:Black 45, magenta 75, yellow 90, cyan 105.

two colour printing

three colour printing

four colour printing

The halftone dots create a rosette pattern, which aids the eye to view the image as it was meant to be originally

The silk screens used were made up of a grid of tiny dots, so when it was print-ed, the human eye viusally mixes the coloured dots to reproduce all the colours of the original.

The angles were detrimental to viewing the image, black was at 45 degrees, as it was the least visible angle to the human eye, as opposed to yellow, which was the most visible at 90 degrees. (see last page)

Colouring Images

tones, tints and overprinting.The nature of an image can instantly be changed and enhanced by merely chang-ing the tone, filter or levels of the image in photoshop or other such photo editing software.

Monotones are a single colour image, Duotones are two colour images, tritones are three colour images and quadtones are four colour images.

First the image must be converted to grayscale, quite similar to the tradi-tional method of making negatives for production.

After this channels can be tampered with and colour levels respectively to bring out highlights and shadows within the image.

Full colour

monotone

duotone

tritone

Tints andOverprinting

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Tints are used to maximize an images potential, and is a cost effective when considering a print job. They also help to keep an images uniformity, and give the image more strength, density and depth.They are also commonly found on packaging, alongside registration marks.

Overprinting is where an ink is printed over another to create another colour, a good example of this would be screen printing, or bad trapping where colours print on top of each other.

Printing Processes

Before a job or piece of work can be sent off for printing, the choice of the print process is relative to the choice of print materials, as well as available resources.

An application used in all the commercial printing is what is known as “make-ready” which is all the actions taken on a press before the first good copies are produced.

This includes setting the press up to accept the size and wieght of the substrate used, putting in the plates, sorting out the right ink and colour of ink on the press, adjusting the folder (see web-fed), and making sure the image is in the right position.

Make-ready is a vital part of commercial printing, as the cist if the job, quality and the final outcome is dependant on this part of the process.

Also known as reprographic printing, it offers a resource to clients and designers alike. The latest industry standard software enables us to automatically check and impose artwork easily before submitting accurate colour proofs in a digital format.

PDF workflow and CTP system are networked with the presses which allow the printers to pre-set colour data and important colour calibration information.

actions to take before

commercial print

Printing Processes

Industrial &commercial

A majority of the processes require the paper to be either sheet-fed, or web-fed.

The difference between the two being that sheet fed is when a print job is single sheets mechanically fed into a printer, whereas a web-fed printer is a continuous sheet of substrate, enabling a print job to be produced alot quicker, as it does not have to slow down to pick up a sheet.

The predominant process used in printing today would be offset lithography, which uses huge rollers to feed paper through sheets of paper,

Ink rollers

Plate cylinder

Blanket cylinder

Impression cylinder

Dampening rollers

Paper

Sheet transfer cylinder

Printed image

The area is treated chemically so it accepts ink (grease) and rejects water, while the non-image (background) does the opposite.When the plate presses against the surface of the paper, it is only the image that is printed.

Ink rollers

Plate cylinder

Blanket cylinder

Impression cylinder

Offset lithography has as many advantages as it has disadvantages, it has a brilliant image reproduc-tion, especially of detailed images, but can sometimes have problems with colour variation due to ink and water balance.

Thanks to CTP (computer-to-plate), which esentially tarnsfers an image direct to the plate, which cuts down preperation time.

To ensure the best possible outcome it is important that the designer talks to the printer. The printer is familiar with the process, their equipment, the type of plates, and file formats required for a job. Which is vital when printing en masse.

Using this particular pro-cess, a larger variety of substrate can be sued, such as a gloss, satin, matte, or just denser paper.This is due to the rub-ber blanket absorbing the pressure and texture on the substarte which can usually cause creasing or tearing, which leads to a botched job and a big headache for the designer, printer and client.

Offset Lithography

FlexographyFlexographic printing was originally basic in quality. But due to technical advanc-es in the past few years have all contributed to the quality of the flexographic printing press. The most noteable advance-ment in flexograpy have

been in the printing plates, including improvements to the plate material and how the plate is created.

CTP has been a good im-provement in the industry recently. Companies like Dupont, MacDermid, Kodak

and Esko have pioneered the latest technologies with advances in washout and bringing screening technol-ogy to the next level.Laser-etched ceramic rolls are used now that greatly imrove the quality of print, full colour printing is now possible. Some of the finer presses, in combination with a skilled printer, produces a quality that rivals the litho-graphic process. One ongo-ing improvement has been the increasing ability to re-produce highlight tonal val-ues.

Gravure

Gravure printing is an intaglio printing technique, which takes its origins from traditional methods such as aquatine, etching, engraving, and drypoint. The image is made up of small indents on the printing plate. The dents are quite like cells, which are filled in with ink, with the excess scraped off by what is known as a doctor blade.Afterwards a rubber roller presses paper onto the plate and into contact with the ink in the dents/cells.

Printing plates for this process are normally

made from copper and can be produced by digital engraving or laser etching.This method of print is primarily used for large scale, high end runs, for productions such as magazines, catalogues, packaging, fabric printing, postage stamps and plastic laminates.

Both Flexography and Gravure produce similar quality, however only a huge volume job makes a gravure print worthwhile, as flexography is cost effective for a smaller low volume job.

Substratewhat paper is suitable for the job?

When selecting, specifying then buying paper, careful measurements must be taken, when establishing the quality and quantity required. In the case of the client supplying the paper, the printer has to be consulted well in advance to ensure the equipment used will be able to take the substrate, and be able to go through the printing and finishing processes.

Basic factors include;Weight, which is measured in gsm, for example, a retail flyer would be printed on something like 100gsm gloss, whereas an exhibition booklet would be on 160-180gsm matte/gloss dependant on the context and content of the printjob.

This is an example of what matte looks like,

using offset litho process.

Shade or tine has to be specified, as paper manufacturers often have their standard shades, with their own codes and names. But when a special shade or spot colour is required, its advisable to send a wide samples for colour matching purposes.

In some substrate they show different colours under certain lighting conditions, also known as “metametric”White, for some part of this reason, is the most difficult shade to match and specify.

Ink&Toner

print process determines choice of ink

Despite paper being the major factor when considering print cost, the cost of ink is also vastly significant. Each printing process each requires specially formulated inks for that certain process.

The differences in the ink formulation for each process allows a certain press or substrate to be used, for example, toxicity issues in food packaging, drying requirements, printing onto a glossy surface, etc.

Inks for gravure or flexography are liquid, and some are a paste, as those used in offset lithography.

I will briefly outline types of ink, and thr processes within them to attain a print of high standard.

Most inks are made by mixing the ingredients below into a roll mmill that breaks thm down until they have a smooth consistency.

Pigment in powder form or dye, gives the ink its colour

Resins form the binder for the pigment

Liquids make the ink fluid so it can be transferred onto the rollers and blanket. Acts as a vessel for the finished ink to travel on

Drying InkThe 5 main methods to dry ink are; evaporation, chemical curing, heat setting, penetration abd oxidation

Finishinghow to instantly give a publication or printjob an extra zing

The only way to effectively describe and communicate what finishes are available is to show some examples. Keep in mind any of the following processes are best discussed with your printer before attempting them.

This is a high quality flyer promoting drum and bass collective subfocus. Printed on high gloss 100gsm substrate, the finish used on this is called spot varnishing. This can be done on a press with a seperate varnishing unit added and with UV drying. Commonly found on books, cartons or anything with a brand or logo.

Another printjob for dance music promotion.This process known as UV coating, is similar to spot varnishing, except UV coating is applied, it creates a heavy, slightly raised relfective coating.

Block print, hot stamp, heat stamp, foil emboss or foil stamp. These are all the same names for the same process.Involves a foil, or a coloured tape that is pressed onto substrate using a heat press.The transfer uses a die, or brass, which is bascially a different sort of plate in which to print with.Gives a job a professional look every time, can also be used in embossing or debossing.

I finish with die-cutting. This is a process which involves a piece of work being cut mechanically, to ensure optimum accuracy, with a slick, crisp look. Used in a variety of contexts, but usually found on limited edition packagaing, or most recently dorset cereal packets.

All processes tha convert printed sheets into bound, folded and comleted publications are known as finishing operations.Always remember to check what colour you are using for a document, what sort of substrate will work with your design, what ink will work with your colour scheme, and finally, make sure the finished piece has something to remember it by.

Designed, published and edited by tommingsdesign. 2009