The processes in printing are several very complex, which is why designers graphics we know from start to finish to achieve our objective , that of properly communicate any message.
The knowledge of these processes does not imply a mastery of them, however as we know and understand better, the better decisions we make about the same and this is reflected in the results you get.
The postpress is the last process of production after printing, and includes all the finishing processes, manipulated, joining pieces and packaging.
Knowing all these processes we may be able to choose correctly between the different types of paper that exist and determine the method most appropriate print and the type of finishes that will give our printed, according to our budget and we should give the diffusion our message.
At the end of the course the student will differentiate the types of finishes that are carried out within the postpress process and select the most appropriate in accordance with the requirements of presentation and quality of the project graph to make.
The process of design and its relationship with the postpress
1.1 Features and materials for the production of a project best graphic design .
1.2 Selection of the system of printing.
1.3 Selection of substrates and inks.
1.3.3 Other media
1.3.5 Other materials
1.4 Selection of finishes.
1.5 Quality control of products printed.
At the end of the topic the student will evaluate the importance of all the separate elements of the postpress stage that must be considered within a graphic production process.
The printing process can be divided into the following 4 stages:
- Design Phase
- Pre-press stage
- Stage of production or release .
- Stage or post press finishing
The responsibility of the graphic designer is not limited only to contribute to aesthetics and creativity in solving a problem of communication , you must know all the tools you have at your fingertips, the limitations and scope with each, and the costs and time it takes at each step, with this knowledge, the designer will be able to provide an adequate solution to every problem of communication that comes your way. Summarizing we can say that the graphic designer's responsibility starts when you decide to solve the problem that has been proposed, and ends, literally, having the solution thereof in his hands, ie to have the product finished graphic. And it must respond to the expectations that were raised from the outset in terms of quality, cost and communication of the message.
Of the four stages that a form is submitted, it is only the first in the design, where it enters play our creativity and in which we intervene directly in the other three come into play and our knowledge of the intervene indirectly by monitoring since these stages are usually performed by third parties.
Definition of postpress
The printing process does not end when the paper comes with the image printed. After that still need to make all finishes to the left printed as planned These finishes can be many and varied cuts, folds, elevations, bindings, coatings, laminates, pierced, hot-stamping, etc.. all these processes are called postpress. In short we can define the set of postpress processes followed after printing, so that our form is completed and ready for use in communicating a message.
1.1 Features and materials for optimal production of a graphic design project
It is equally important to know that you are printing with which materials and the printing system to be used.
The same original, printed on different paper types with different inks and other printing system can give opposite results. You need paper and ink set which will be specified for a particular print, to work well with both the print system to be used, as with the aesthetic result you are looking for in print.
1.2 Selection of the printing system
The following explains the six systems most important print, operation and method of work .
It also marks a relation between the printing system, the quality it offers and its use, and highlight the advantages and disadvantages of each.
Printing systems are:
1. Offset (sheets)
It is an indirect printing process in which the shape containing the picture (board) does not touch the media, but that transfers the image to another cylinder ( rubber ) print. This printing system is ideal for medium run lengths, ie from 1.000 copies in sizes from letter to eight trades.
1.A Offset (rotary)
The printing system is equal to the specifications, the difference is the greater speed of printing, the paper comes in rolls. A rotating coil is mainly divided into five parts: carrier coils, drives printers , superstructure, folding, conditioning bands.
Types of rotary. Presses for newspaper / press printing are intended for daily or weekly press, characterized both by its large paging , high-speed runs and need of completion. Most of these machines include finishing units, folding and cutting.
The typography is to deposit the ink on a printing element etched in relief and back, to apply, then a sheet of paper. The pressure exerted on this sheet will allow the ink deposited on it. The level difference created by the engraving prevents the ink reaches the gaps.
In this process involved printing the paper machine, type or print and ink. This type of machine is used to Suajes, pleco and folio.
Flexography is a variant of type. It is printed on presses with rubber photopolymer plates or cylindrical plastic , bearing the image in relief. Very fluid inks. Also called aniline printing.
It is used to continuously print jobs, especially in flexible plastic film holders for product packaging and adhesive labels for packaging chain.
It consists of a fabric stretched over a framework in which there are areas without blocking where the ink will seep up to the media. The other areas will be covered to keep the ink will not be missed. This printing process involves:
- The substrate (paper, plastic, cardboard) of different thicknesses
- Silk-screen display
- The standard
- The machine
- The ink.
The substrate can be any type, flat and even irregular volume .
5. Gravure (cylinder)
Is a cylinder of steel covered with a thick layer of copper smooth, in which, by means of gravure system or electronic recording, it records the negative image buried in the copper layer. Cavities will be formed and which will endure the ink and paper deposited by pressure.
Huecográfica ink is liquid and contains a large amount of solvent that evaporates quickly and leaves the dry pigment on paper. To speed up the drying process, the paper web, after every body, passes through areas of air or infrared heat.
This printing system is used for large-circulation magazines that require high image quality, since it is able to maintain a stable colored all controlled circulation publication. It is also used for printing plastic and flexible packaging products for food .
The high cost of preparation, is amortized over the printing speed and print quality. This system because it is rotating, also known as rotogravure.
1.3 Selection of substrates and inks
It is important that we take into account the type of substrates and inks used in the production of a graphic, because sometimes these will determine what type of finish we can use it.
The substrate is the surface to be printed. It is usually paper, but can be any other material, from plastic films or metal to fabric. The type of substrate used directly affects the final quality of print. In fact, substrates and semiflexible smooth finish, good consistency on the surface, neutral, with appropriate binders, fine porosity and with adequate moisture, allow the best prints. Be careful to choose a suitable printing system to the substrate you want to use. Remember that not everyone has the same capabilities.
Could we imagine a world without paper? Were there now books , magazines, newspapers, if they had not invented the paper? What would not the role of school activity, storage, transport and storage of food or other goods, work in an office , the health staff ? The great development of the paper is due, firstly, the relationship value / price that has allowed prevail over other materials in many applications.
Throughout the centuries, the role has proven to be compatible with the technical advances that have been linked to the development of new paper products: offset paper, paper for fax , photocopier paper, continuous paper for computer , etc.. The paper is therefore perfectly adapted to technical progress (speed of the machines, presses, packaging) and new uses (fax, beverages, food use toilet paper, etc.)..
The printing paper is today an important support and supply vehicle information and advertising . Advances in transmission electronics of data have not reduced, but on the contrary, have increased their use.
Versatility of use
The International Pulp and Paper Directory has recorded a total of 457 varieties of paper. With hundreds of end uses, paper satisfies communications needs, cultural, educational, artistic, hygienic, health, distribution , storage and transportation of all types of goods and, according to them, the product is designed to meet certain requirements texture, strength , softness, absorption, etc..
In the case of paper, there are several points to be taken into account when choosing:
1. Weight, ie, the thickness of the paper. It is measured in g/m2 or points.
2. The color of the paper, since it will affect all other colors , both in tone and brilliance.
3. The finish of the paper, ie the surface can have coatings or textures, can be shiny or matte.
On its surface, we can classify basically paper and cardboard covered, not covered and embossed or textured. For its size can be classified in paper, paperboard and cardboard.
The print quality of paper depends on the following physical and chemical characteristics:
• Physical characteristics
- Weight or Size , weight is measured in g/m2 and the size is measured in points. One point is equal to 0.001 to 0.025 in. or mm.
The compressible blankets have proven a valuable resource in the printing of paper slightly out of calibration, maintaining sharpness, smoothness, strength and cleanliness. Agree that the caliber of the papers is as uniform as possible, as poorly calibrated papers originate defective prints.
- Porosity is the number of holes per unit area which presents the role.
Highly porous papers absorb ink printed film and although it favors the drying, the overall appearance of the form may be affected. Remember that paper is a highly porous material, the air content of common stock ranges from 50% to 70%.
- Consistency in its surface , is the degree of detachment from the paper lint.
Papers tend to lack consistency or shredding lint easily during the printing process, often forcing condition inks, reducing its detrimental mordencia concentration.
- absolute humidity is the amount of water considered in percentage points is contained in the paper.
The elongation or contraction experienced by the papers by absorption or water loss is intrinsic to its constitution . Careful studies have shown that the absolute humidity lithographic appropriate roles is between 7% and 8%, but depends on the type of paper and printing process. For stability to preserve its stacks of paper or cardboard with original covers before going to print.
- wrinkles and ripples . If the paper has a serious problem of wrinkles or ripples, not be printed, as a wrinkled paper is not acceptable. Sometimes the paper is wrinkled at the time of print and must find a reason to avoid this problem. Generally moisture differences are the cause of undulations, so you have to put the paper to eliminate the problem.
- Absorption or penetration , is the migration of the ink through the fibers and pores of the paper immediately after printing.
Highly absorbent papers are not usually appropriate for a good offset printing. In anticipation of this, no inks that have made to preserve the printed film on the substrate surface, preventing penetration.
- Flexibility and hardness , is the consistency that has the role in its formation.
Very hard papers are more difficult to print on offset with a suitable quality for printing so that the papers should be used compressible blankets and special inks.
- Address of the fibers . In its initial development roles consist of a dispersed fiber 2% to 98% water. Upon arrival to the band (felt fabric), the fibers will lose water and are moving in the direction of making paper. In sheet-fed presses or sheet, the orientation of the fibers must be parallel to the axes of the unit printer . To determine the direction of the fibers of the paper takes a tear sheet and parallel to one side. Then another cut is torn but perpendicular to the first, the cut that follows a straight line represents the direction of the fibers, while the other will cut zigzag.
The direction of the fibers affects where they go to make bends, because if they are perpendicular to the fiber direction, may not be well marked. And if you plan to bind, it should be fiber direction parallel to the bound
- Tensile strength , is the opposition that has cut the paper when subjected to two opposing forces. Roles of low tensile strength do not support the traction of the forceps and tear.
- Delamination is the tendency for some paper or paperboard, to separate into layers or form bubbles at the time of printing.
This problem may be in paper or low-quality cards that contain a high moisture content.
- Double Sided , differences between the two sides or sides of the paper: cloth and felt, are important through their influence on other properties of paper. As a general rule, the brightness and the smoothness of the two sides is different, so does the tone or intensity of color can be different, because most dyes have higher affinity for the fine and charges, which are in greater concentration in the side felt. The two sides behave differently during printing, so it is important to identify them before starting work.
Identification of the sides
The fabric side is generally rougher than the felt side, due to the mark it leaves the forming fabric of the paper machine, as it is generally open or porous fabric side and closed with a texture side felt fine. Usually this side is printed. The difference in texture between the sides and felt fabric usually noticeable to the naked eye, so folding paper can be identified, directly comparing the two surfaces. On paper with watermark, you can tell because the watermark is usually read by the hand felt.
- Bulk density and apparent, the density of the paper is probably the property most important. Provides information about the structure of the sheet and is related to other properties of paper, especially: porosity, stiffness, hardness and strength, but in fact affects all optical and physical properties except basis weight. It also affects the absorption and ease of printing.
The apparent density of paper is affected by many factors, including: the number of joints between fibers, which depend on the diameter and flexibility of the fibers, the pressing of the wet sheet, the amount of glucose , the presence of materials that fill the gaps on the sheet, and so on. The density of paper or cardboard is its weight per unit volume.
The specific volume or bulk is the reciprocal of the density property, or the volume in cm 3 of a gram of paper. In some cases it is customary to use bulk, when dealing with bulky paperwork, but can be considered equivalent in bulk density and what affects one also applies to the other. This property is important for manufacturers of books because if there are variations of consideration, books will have different thickness, causing problems in their binding. It is also an important property in absorbent paper and pancakes (fluffy roles, such as crepe paper).
- Stiffness is the ability of paper and paperboard or cardboard to prevent deformation when subjected to stress. However, the stiffness is an extremely important property for many uses of cardboard or paper, so that in some cases it is desirable that this is high, such as paper and cardboard for printing or boxes. In contrast to other uses such as facial tissue, requires that the stiffness is very low.
- Paper Smoothness is a property that affects both the appearance and functionality of the paper. From the point of view of printing paper, refers to the perfection of the surface of a paper and to the extent that uniformity resembles the surface of a glass plane. It is said that the paper has a smooth or rough texture, meaning that surface irregularities are small or large. The industry 's role is often called satin finish or the quality of the paper surface or smooth.
The roles are very distinct in their relative smoothness, since smoothness depends on other properties of the paper. The short fibers produce a smoother paper than long fibers. The preparation of the paste and how they are distributed to form the paper fibers in the fabric of the machine, have great influence on the formation and smoothness. Uneven training reduces the smoothness and the basis weight increases.
A good flatness requires the absence of gaps between fibers and fillers, or be free from: brands of cloth or felt, fiber balls, foreign materials and battered areas on the paper.
The appearance of a sheet of paper is determined not only by their physical characteristics stated above, the combination of their optical properties.
- Opacity or transparency.
- Brightness and Color
- Opacity is the property that holds the paper to allow or disallow the passage of light through it.
Opacity will also affect the ability of paper to absorb ink from one side without noticing the other.
To make the paper suitable for printing are considered in terms of opacity is required opacity is 90% to 92%, at least, although there may be exceptions such as vegetables (Opaline).
- Whiteness , is the ability to reflect the role of white light falling on it, and especially the uniformity in reflectance.
- Brightness, is the ability of a paper to reflect light falling on it, ie its ability to mirror, we must be careful not to be confused with whiteness.
- Refined and squaring . It is very important that the papers reach well refined and square cut to print on sheet-fed presses, because if you make the refined dull or nicked blade on the guillotine, or jagged vertical bar at the outlet of the larks ( in the manufacture of paper) will generate a lot of fluff. Therefore, it is desirable that the papers reach well refined, cut square and free of kaolin or charges.
• Chemical Characteristics
- acidity or alkalinity, is the nature acidic, neutral or alkaline paper presents the printable side, ie, its value pH . The pH of the paper affects the drying of the inks, because for every unit increase in the pH of the solution or the surface of the paper, doubles the time of drying of the inks. Papers slightly alkaline neutral on its surface, excellent for printing.