In order to turn the design into a finished piece of work, a number of processes must be carried out, such as selecting the print method to be used, preparing the artwork for print and selecting the stock that is to be printed on.
Printing is the process by which ink in the form of a design is applied under pressure to a substrate to leave an impression.
A designer communicates the printing requirements for a job through a print order, which includes the printing process to be used, the stock, the print run and any special requirements such as specific colours.
Print order is the sequence in which the different colours used in a job are laid down during the printing process. For the four-colour printing process, the order is cyan, magenta, yellow and finally black. The acronym CMYK implies a sense of order; cyan, magenta, yellow and black(key). While work is frequently printed this was, it is common for printers, upon seeing artwork, to change this order. It it often changed if the artwork contains large panels of flat colour, or if the printed work contains any overprints, requiring inks to be applied out of sequence. In either case, it's best to check with the printer how they intent to print, prior to setting any final overprints.
Gradients and Tints;
Tints and gradients can be used to provide a delicate and graphic alternative to a simple solid sills for colour coverage. The two are linked as a gradient is essentially a tint of increasing or decreasing weight, while a tint is a specific gradient of a colour.
A gradient uses one or more colours that combine to create the colour effect. In a two-colour gradient, one typically gets stronger or darker as the other gets weaker or lighter.
A tin is a colour printed at a percentage of ten to 90 per cent of a full solid colour and is created using half-tone dots of different sizes so that there is colour dilution from the substrate.
There are four main processes used by the commercial printing industry - offset lithography, gravure, letterpress and silk screen - all of which differ in cost, production quality and production rate or volume.
Lithography produces good photographic reproduction and fine linework on a variety of stocks. The printing plates are easy to prepare and high speeds are achieved, which helps make it a low-cost printing method.
Offset lithography is available in sheet-fed printing presses and continuous web presses. Sheet-fed presses are used for lower production runs such as flyers, brochures and magazines, while web printing is used for high-volume print jobs such as newspapers, magazines and reports.
A method of relief printing whereby an inked, raised surface is pressed against a substrate. Letterpress was the first commercial printing method and the source of many printing methods. The raised surface that is inked for printing may be made from single type blocks, cast lines or engraved plates. Relief printing methods can be identified by the sharp and precise edges to letter and their heavier ink boarders.
In gravure printing, the printing elements take the form of cells. As a rule, the printed image is transferred to the cylinder with a diamond stylus using electromagnetic gravure process. The cylinder is inked completely for the print run. Then a doctor blade strips the excess ink off the surface and the ink is left only in the indentation. A rubberised roll presses the paper against the cylinder and the ink remaining in the cells is deposited on the paper (direct printing process). A doctor blade is a thin, straight steel rule in gravure printing. In screen printing a doctor blade with a rubber or plastic edge is used to distribute the ink on the screen.
Rotogravure is more common commercial relief print process in which an image is engraved into a copper printing plate that is pressed directly against the substrate. Using a laser or diamond tool, small cells are engraved into the plate to hold the ink that will transfer to the stock, with a separate printing unit for each colour. Rotogravure is a high speed printing process that can give the highest production volume and has the widest printing process. Rotogravure is used for very large print runs.
Another method with the image is carried by surface differences in the plate is flexography. This process creates a rubber relief of the image, which is inked and pressed against the substrate. Developed for printing packaging materials, the process was traditionally a lower quality reproduction method, but it now competes with rotogravure and lithography, particularly as it can print on a wider range of substrates due to flexibility of its plate. Flexography is used for medium to large print runs.
Screen printing is a relatively low-volume printing method in which a viscous ink is passed through a screen- originally made from silk - that holds a design, on to a substrate. Although a relatively slow, low-volume and expensive printing method, screen printing allows images to be applied to a wide range of substrates, including cloth, ceramics and metals, which are beyond the pale of other printing methods. The viscous inks allow specific colours to be applied and can also be used to create a raised surface that adds a tactile element to a design.
A designer can choose from a wide range of stocks on which to print a job. Stocks differ by size, colour, texture, composition, printability, and various other factors that need to be taken into account during the selection process.
GSM, grain paper direction are key physical characteristics to consider when selecting and using a stock for a publication.
GSM (grams per square meter) is a weight measurement that is part of a paper specification based on the weight of a square metre of the stock. The higher the GSM value, the more weighty a stock feels. An A0 page is equal to one metre square, meaning that grams per square metre equates to the weight of a single A0 sheet. 841mm by 1189mm.
Paper produced on a paper machine has a grain because the fibres form which it is made line up during the manufacturing process in the direction that it passes through the paper-making machine. The grain is the direction in which most of the fibres lay. This characteristic means that paper is easier to fold, bend or tear along its grain direction.
The direction of fibres in paper for laser printers, such as those found in offices, typically as a grain that runs parallel to the long side of the paper to allow it to pass more easily through the paper.
Paper types and print quality;
Many different types of paper stock are available to the designer. For example, this book prints on four different stocks: woodfree is the main stock used, a matt art, glass art and a coloured woodfree. In addition to adding different colours and textures to a print job, these also have different printability characteristics and cost. Paper characteristics that affect printability include its smoothness, absorbency, opacity and ink holdout. The table opposite is designed as a quick guide to the characteristics of some main paper types.
The smooth surface of these stocks is obtained through the use of filler elements that may be polished with calendering rollers. They are typically glossy as well.
Stocks have different absorbency levels, which is the degree to which the ink penetrates it. Printing inks tend to dry quicker on absorbent stocks, but absorbency may cause problems such as dot gain.
Opacity is used to describe the extent to which whatever is printed on one side of a sheet shows through and is visible on the other. High-opacity papers have no show-through.
This is the degree to which a stock resists ink penetration due to its relative lack of absorbency. Coated stocks may be particularly prone to ink holdout as the ink sits on the surface, which in turn increases drying time.
Uses of different papers, the production manual;
The weight of paper is measured per unit of area in grams per square meter. The weight of paper grammages range from 7 to 225 grams per square meter.
- Lightweight printing papers - approx 40g/m²
- Newsprint - approx 50g/m²
- Poster papers - approx 60g/m²
- Art papers - approx 135g/m²
- Glossy illustration paper - 0.75-0.8
- Matt coated illustration paper - 0.75-1.0
- Slightly voluminous paper types - from 1.0 onwards
Paper has different qualities according to the way it is manufactured and according to its composition. Pulp is the basic raw material for paper, it is made up of raw materials such as wood and cellulose, cellulose gives the pulp sustainability.
In industrial paper production, the sheet making process takes place on a paper machine. The paper pulp is 99 per cent water. After cleaning the pulp several times, a large portion of the water is drained which creates a paper structure. Fillers are additives in paper, they fill in the gaps between the paper fibres, the composition of the fillers determine the opacity of the paper, also the degree of whiteness and smoothness.
Pulp paper is something that can be made at home in a few easy steps. Creating pulp paper can be very useful and effective for creating a certain look, depending on what it is being used for.