PRESS

After the explanation of paper and film, let’s learn about the printing press and pressing for processing them and making them visual. Let’s see how the prepared films are transferred on the paper by means of patterns in printing.

Types (Techniques) of Printing

The process of plotting with the help of moistening and ink is called offset printing. The grains created by the points on the film surface called tram on the surface of pattern fill with inks transferred by means of rollers. The filled points transfer the ink on the rubber on the boiler called blanket and the rubber transfers this on the paper.

  • Offset printing
  • Letterpress printing
  • Gravure printing
  • Flexo printing
  • Screen printing
  • Digital printing

The technique of offset printing consists of 2 groups.

  • Layer offset
  • Rotation

The Angles on the Color Dots (Tram Angles)

Various colors are created because of the printing of the points on each other with angles and the characteristics of the inks are transparent (not covering). In order to produce a good printing; a good film, a quality ink series, and sensitive machine settings for a proper transfer work are needed. Some types of making a quick and healthy printing in the printing processes and the terms used.

  • Signature printing method
  • Normal Offset Printing Method
  • Skirt-Grips Offset printing method
  • Both Sided Printing
  • Grips- Grips Offset
  • Skirt-Grips Offset
Press

Layer Offset

The black areas on the film are left lightless on the pattern by exposing with the pattern light made sensitive with special emulsion. Other transparent areas are roasted by satiating with light. After that, an emission to accept paint is created when the surfaces on the pattern where there is no light pour their frits during developing.

Since the emission created does not hold water, it holds the paint coming from the rollers and transfers it on the rubber. The blanket though transfers the paint on the paper just as it gets. Therefore, the points on the film completely pass on the paper according to the color of the ink. Today the offset printing is made according to 4 primary colors. We call this Trichromatism printing in typography.

Signature Printing Method

This is a technique used for multipage works such as book-catalogue, etc. The purpose is that the pages follow each other in case of the folding of the paper and that the process of admixture decreases. In addition, it enables the pictures which can be on the pages facing with each other, which complete each other and which are the continuation of each other to continue with the same color tone.

Normal Offset Printing Method

This is a technique of making printing on the front and back of the paper by printing with 4 patterns and 4-color printing in the formats which are suitable for the machine size. It provides savings both from the number of patterns to be printed and the time to be lost due to the machine settings.

The move of the paper in the machine is in the way that the apparatus that we call grips transfer the wide side of the paper to the other printing units by holding it. We call the part of the paper held by the grips “Grip Edge”.

In addition, we call the thing adjusting the printing on the paper to enable it to be printed on the same place before the paper is taken by the grips “Poza”. In the normal Offset printing, this is a process of printing on the front and back side of the paper with the same poza and same grips.

Etek-Makas Revolta Printing Method

The spot held by the grips is grip edge and the spot pulled by the poza apparatus is poza. So, what is called the remaining two sides of the paper? The side remaining behind the spot held by the grips is “Etek” and the side remaining opposite the spot pulled by the poza is called “Karşı Poza”.

The purpose is same in this printing technique. Color printing is made on the front and back of the paper with 4 patterns at a time. That is, the purpose and the results obtained are the same as the Offset method. The difference is only about the method. At this time, the paper is printed in a way to be etek-makas by make it roll over. Poza is still fixed. Karşı poza is an apparatus mostly used to print the materials on the front and the ones on the back in the same setting during the both sided printing.

Web Offset (Rotation) Printing Technique

In 1912, Casper Herman (Vomag) started to manufacture the first rotary machines. This is an advanced version of the offset printing system. This system is used for the print with a high circulation in today’s world. Nowadays, the advantages provided for the works with a circulation in the printing field are a lot.

  • The most important characteristic of the web offset (rotation printing) is to be in the characteristic of printing on the paper folded in BOBBIN.
  • As a printing system, web offset machines are not so different from the typical offset machines printing in layers except for the way of using the paper (layer/roll).
  • The most important characteristic of the web offset is that this is both technical and commercial. However, some rotation experts believe that better results are obtained from the layer offset. The paper which paint transfer is made is quick-frozen with a temperature decreasing up to +13 degrees by passing from 110-140 degrees and finally, the paper gains brightness as a result of the quick drying of the paint. The paper emission passes from the silicon, from the silicon reservoir before it comes to the folding funnel. Therefore, this glaze gains a + value at this point.
  • Because these machines carry out the certain works and they are manufactured for these works, apparatus are added according to the requirements and qualities of the work (For example, devices such as folding, cutting, blending, packing, drying, etc. are added).
  • In the web system, both units consist only of two patterns and two rubber boilers. The printing is carried out from the rubber to the rubber. The paper in bobbin passes between two rubbers and one rubber prints on the upper part and the other rubber prints on the lower part. Therefore, both sides of the paper are printed.
  • The most important characteristic of the web offset ink is drying. So, the ink which is fixed in the heat should be used. Ovens or tunnels should be used to provide drying between the final printing and folding for this.

Some technical characteristics of the web offset (rotation) machines

To be valid in every unit, in these machines, the remote control and printing setting of the machine are carried out with the central control system. We see 2 types of systems in the rotation printing technique. Coldset (without dryer) Heatset (with dryer) We have only talked about the Heatset printing so far. Coldset printing cannot be print on the machine printing on the uncoated papers such as High Grade Papers and such as newspapers and which does not have drying tunnel.

  • Central control system
  • One or multiple printing units
  • Bobbin stands
  • Paper tensile
  • Dryer
  • Cooler
  • Folding
  • Cutting
  • Mixing
  • Job count in desired number

Screen Printing

For centuries, the cloths have been printed on the templates in China and Japan and sold to many countries around the world. In the beginning, the figures could not be printed on the templates such as paper and leather without leaving tie tracks. The template tracks remained on these surfaces at certain intervals. In time, figures scratched from paper were attached on these templates used in the Far East; the printing results were obtained without leaving tie tracks. In order to print without the tie tracks, a carrier assembled on the frame and surfaces with pores that are paint permeable are needed. We call this GAUZE and SCREENING CLOTH in screening printing.

The paint is imposed on the cloth with a tool that we call scraper (the firm, rectangular object held in the craftsman’s hand that is moved back and forth on the sifter to pass the proper paint). This paint passes through on the cloth only from the parts of gauze (screening cloth) which are uncoated. Since the thin gauze threads do not avoid passing of the paint, the paint spreads on the surface of the material printed in a clean and decent way. The kind of printing carried out like this is called Screen Printing or Stencil Printing.

Since this printing method is rich in terms of practice type, it is practiced from the simplest artisan workplaces to the greatest factories.

Recently, stencil printing has competed with roller printing. Because stencil printing can make easy and quick-changing printing as a simpler and cheaper method, it is more suitable for the printing for low circulation. The handcraft of the craftsman to carry out this work is very important.

Silk gauzes are tissues made with snap pin method that does not move in any direction. Later special gauzes were made from natural silk for stencil printing.

After the release of the synthetic fiber, the silk gauzes lost their importance (The reason for this is that the synthetic fiber was preferred due to its qualities such as high chemical resistance, flexibility and durableness). The most suitable fiber for gauze is the polyamide type.

SCREEN PRINTING METHOD

(Screen printing, stencil printing, film printing)

It was spread from Japan to America and then to Europe. It is especially used for the advertisement printing. As known, in the offset printing, the printing is only carried out on the paper and layers in the kind of paper or the items in the kind of bobbin directly. In the screen printing, the printing is carried out not only on the paper, but also on paperboard-cardboard-PVC (soft and hard)-various plastic (synthetic) items, metal, glass-ceramic, textile, etc. items. The success of this printing method is about the workplaces knowing the technique well (ink is important in this printing method), using ink which is qualified and appropriate for the work. In this printing method, silk wires are used instead of patterns. This is a kind of veil called pure silk, nylon perlon and metal fabric. When the veil is holey like a wire, it is called screen printing. The thickness of the paint is 6-10 times more than the letterpress printing. Serigraphy is carried out in 2 parts.

Preparing a Template

First, in order to make the printing, wood or metal frame, synthetic or metal silk scraper is needed. The silk is stretched on the frame, the frit pours on the silk in film (it can be a pin, stapler, sealing). The lights are on, sufficient poses are struck by placing the film desired to be printed between the templates and posing apparatus. The parts getting the light are cleaned with the chemical bath. Then, the template is washed with pressurized water. The posing duration is understood after a few tries according to the distance between the light and the templates and the intensity of the light.

Printing

The printing is carried out with two ways.

Manually: Paper, cloth, plastic, leather, etc. on which the printing will be made is put on a flat surface. The template is placed on the material on which the pattern will be printed. Some amount of paint is poured inside the templates and it is pulled one-two times with the scraper on the pattern. The craftsman carrying out this pulling must be skillful and the movement and power of the printing made manually must be equal. Then, these printings are put on the shelves individually to dry.

With Machine: This is very simple. The templates are connected to the machine. The printing is carried out directly.

Important Information in Serigraphy

When the printing is carried out on the plastic printed materials such as acrylic, polystyrene, the characteristics such as sticking well and drying quickly, resistance to the light in high density are sought in the paints. For example, if it’s done on cloth, small desk flags, flags, and special fabric dyes must be used. If printing is made on the materials such as polyester or polyethylene and if very bright and resistant printing is wished to be made on the special polyethylene inks, on the surfaces glass, metal, specially prepared paints with high density must be used.

Serigraphy inks must be kept in set. Otherwise, they become stiff 8-10 hours later and they may not be used again.

Lithography (Lithographic Printing)

The lithography system is based on the principle that the oil and water do not intermingle, obtaining areas that can be printed or cannot be printed on over the same surface. The section of the printing surface on which the printing will be made draws the ink and the other part draws the water. The main principle of Alois Senefelder who invented this kind of printing was: when something is written on a porous limestone with oily ink, the oily ink is avoided spreading with the application of an Arabic gum dissolved in water. Some of the solution of gum and ink penetrates on the stone.

If the surface of the stone is cleaned and watered with a sponge and an inky roll is placed on it, the oily ink on the roll is marked on the surface of the stone during the first process and the absorbed part will be accepted by it. The other wet areas of the stone, rejects the ink. Therefore, the form made on the stone occurs again. This form is transferred on a paper by means of printing.

The lithographic patterns prepared on the stone are used only with the typical litho machines. In this printing system, determining the pictures and writing on the stone as REVERSE is about having a special habit for reading and writing them.

Stone is heavy. It is a kind of calcium carbonate. It’s most important characteristic is absorbing water and oil. Lithography printing machines work very slowly. Since their patterns are heavy, it takes a long time to clean and prepare them for printing.

Tiefdruck Printing (Gravure-Intaglio Printing)

This is the most developed industrial printing technique in the world. It serves in magazine publishing, textile and especially packaging sector. It’s most important characteristic is that, it can make indefinite printing. (Because the printing is made on the flat cylinder, etek-grips sections will not be available, the whole surface of the cylinder prints completely.)

As understood from its name, gravure “means intaglio printing in German”. The photos, patterns, writings are made by engraving the copper cylinder by means of

  • Chemicals
  • Diamond
  • Laser

Since copper is not durable, chrome is covered on it. Therefore, the works with high circulation are printed. Its ink is in liquid state. In this system, the parts where the ink is taken and passed on the paper are in a hole. In this system, it is necessary to work more carefully than in the offset and letterpress to acquire a printing which is close to original.

Flexo Printing (Rubber Printing)

This printing is also a part of the “high” system, like the “letterpress” printing. The printing is made with the flexo patterns. It is mostly used in the packaging sector. The printing is made on the nylon or metal folios. Therefore, the flexo printing must be distinguished from the gravure printing. In this printing technique, the density difference between point side and the center is as in the letterpress printing. Also since liquid paint is used in this technique, this difference can seen more significantly than the letterpress printing in certain situations.

The flexo printing machines are “ROTARY” and they make printing on the plastic in bobbin or paper. In this printing technique, only rubber patterns were used years ago, and it was called rubber printing at that time. Rubber pattern is used only for rough works today. Sensitive and multicolor paper and folio printings are made with trams of 48 pieces with photopolymer stereotypes and even 54 pieces. The paints used are used with diluters in aniline with the consistency of ayran and based on the basis of ethanol and they need to dry very quickly. The paint unit in this printing system is quite simple. The feeder roller revolving in the paint reservoir transfers the paint to the roller with tram and the roller with tram transfers this to the pattern boiler. The pattern boiler touches with the printing boiler and forces the paper or folio passing in between.

The flexo printing machines work quite fast. Since the way of working is simple, this system is economic. The photo films may compete with gravure in some works, if not all works, thanks to the high quality created from the stereotypes. The flexo printing system services mostly for the packaging industry.