WHAT IS PAPER?

The suitable layer for printing whose raw material consists of slim plant fibers is called paper.

Characteristics:

The characteristics of the papers change depending on the printing systems. The main requirement which is necessary to carry out the printing is that the ink used should remain on the surface of the paper. The paper should not wear off during the printing and the fibers should be more durable than the paint extract. The durability of paper is much more important in the multicolor printings. If the printing machine has one or more units, the paper can pass from the machine 4 or 8 times depending on the number of the colors of the printing made. The paper should not lose its characteristic during the passing.

The quality of the paper is closely related to the additives in it. Each printing system requires a capability of paint absorption from the paper. The paper obtains this quality with amount of glue in it and the opacity or luminance of the surface. The glued papers give more regulated printing. The papers that has no glue moisten and decay quickly. However, the paint absorption of the paper should have a limit. When printing is made on the excessively absorbent papers, it is seen the paint is passed to the behind. When more than one paint is used, it is seen that a change and maladjustment happens to the color tone. When the amount of paint may not be increased due to the printing, the color satisfaction may not be provided on the pictures on the printed work.

As a result: Even if the reproduction is made according to the original one, the excessively absorbent papers decrease the printing quality.

The more the paper is white, the more the printed pictures shows themselves, become contrast and bright. The papers with more cellulose are more appropriate to the multicolor printings than the paper with less cellulose. There are two reasons for this. They are that the papers with more cellulose are whiter and that these papers are not affected by the sunlight and do not turn yellow.

There is %5 wood in the quality papers. This rate is necessary for the durability and the stiffness of the paper. Otherwise, they may not resist to the pressure during the printing and they may be damaged.

What is Paper?

The Features of the Papers According to the Printing Systems

Offset Printing Papers and the Features

The fact that the papers used in this printing technique are smooth and clean surfaced is not obligatory for the printing quality. The printing is also made on the embossed note papers and patterned papers. In the offset printing, the printer’s felt giving the paint to the paper may transmit the paint to the rough and porous parts of the paper. Therefore, the printing of the slim screening may be possible. However: In the offset, the papers which are smooth, clean and in equal thickness may be made printing more easily.

Letterpress Printing Papers and the Features

In this printing system, because the printed parts are up and stiff, the features and elasticity of the paper surface have importance. The selection of the paper should be made according to the work to be printed. In the letterpress printing, opaque paper is preferred for the multicolor works. Because the surface of the good coated papers is smooth, in equal thickness and both surfaces are made satinette perfectly, the brightness is important in the letterpress. High grade paper pulp may be used for less important works instead of the coating base ones, even newsprint paper may be used for single colored works.

Screen Printing Papers and the Features

It is possible to print on almost any kinds of papers in this technique. Good glued papers give much better results.

The Gravure Printing Papers and the Features

The gravure papers should be in equal thickness, soft and elastic. It complies with the gravure pattern only in this way. Since the paint used in this kind of printing is flowing, the absorbance of the paper is important during the drying. Since the paper should be absorbent, the glue should be less. The wrapping of bobbin is also important in this as in the rotation printing. If the features of the paper are as we wish, the opaqueness and the brightness are not so important.

Rotary Offset (Web Offset) Printing Papers and the Features

The works and newspaper with very high circulation are printed with rotary offset printing machines. The papers to be used in these machines should be especially stiff, elastic and their bobbins should be wrapped in equal tightness. The rotary printing makes 3-4 times faster printing compared to the sheet fed offset printing, that is, the system printing on the stratified papers. The paper should resist to this speed and should not come off (tear). Also, the fact that the paper is wrapped on the bobbin perfectly is important in terms of the machine setting. In the bobbin offset (rotation), because the setting is only provided from the sides, if the bobbin paper passes sometimes stiffly or sometimes loosely, maladjustment happens. Lately, very sensitive electronic devices have been used for this.

Need-To-Know About Paper

The Naming of Papers in the Printing Language

In the printing sector, the paper is classified as high grade paper pulp – lightly glazed paper – newsprint, in other words, by considering the ways of manufacturing. Besides them, there are paper types under any kinds of names and which have different features. Let’s remind you what these types are and the ones which we hear about most.

1.High Grade Paper Pulp:Having more cellulose and less wood in its compound.

2.Lightly Glazed Paper: Having almost equal cellulose and wood in its compound.

3.Newsprint: Having more wood and less cellulose in its compound.

Coated Paper: A quality paper with %5 wood and bright and opaque types.

Onion Skin Paper: Very slim and light paper.

Wrapping Paper: A paper made of paper pulp with low quality and used for the wrapping of the thick and heavy items.

American Bristol Paper: A paper type whose one surface is glossy and with thick basis weight.

Autocopy Papers:A paper type that transmits the same writing on the lower copy when written on the upper copy.

Special Papers

Tracing Paper: A semi translucent paper mostly used by the architects with a slippery surface.

Printing Paper: A paper which is good for reproducing the pictures and writings from the patterns, whose surface is covered with substance which is light-sensitive.

What is Paper?
What is Paper?

The Quality of Offset Paper

The paper is very important in making very good printing and to reach a very fast printing speed. The required specifications of the papers to be used in the offset printing are as follows:

  • Its surface should be smooth (It should not be curl)
  • Its cutting should be decent
  • The paper should be cut decently in the direction of water.
  • It should be inclined to printing (in terms of fiber and filling materials)
  • Its moisture should be normal. 60-65 %
  • It should be good-stored
  • It should not be very dusty.

The Damage of Excess “Ph” of the Paper in Printing

The papers having acidic or basic Ph value cause the deterioration of the presser plates. Because the balance of offset ink-water is a system working with water, the moistness on the rubber is in touch with the paper surface. As is known, because water is a solvent in some way, the acidic or basic influence on the paper causes the anointment of the presser plates and therefore, the volatilization of the plates by reverting to the plate from the rubber. Also this influence increases or decreases the Ph value of the reservoir water by passing to the rollers moistening the plate and therefore to the reservoir water of the press mould.

Paper Backing (Contamination)

The fact that the paper absorbs the ink is generally about the surface. The thickness of the ink on the paper surface is very important. The capability of the paper to absorb the ink is very important. The ink dries on the paper surface mostly as a result of oxidation. If the absorption power of the surface is low, placing the ink on the paper is slow and the incidence of backing happens.

Backing means that if the ink on the printed surface does not dry, it contaminates the paper on the second layer on it. This term is confused with the fact that the work printed in a bold way on the front surface of the paper is seen from behind the paper.

The Waterway of the Paper

The waterway of the paper means the direction where the pulp flows during manufacturing while constantly coming from the reservoir to the wire (grain route). Because the cellulose fibers extends and felt in this direction.

The practical process which is necessary to find the waterway of the paper is as follows: a piece of paper is folded widthwise and lengthwise. The folded parts are slightly moistened and scratched with nail. After this process, the fluctuating side of the paper shows that the waterway is reverse. Because cellulose fibers are broken in this direction and it causes fluctuation on the paper. The other side which is not fluctuating shows the direction of the waterway. The waterway of the paper is ultimately important in printing and binding.

The Determination of the Waterway of the Paper

  • The paper tears more decently in the waterway.
  • It tears more in a hairy and an unparallel way in the opposite way.
  • The paper is firmer in the waterway.
  • The paper expands in the opposite direction of the waterway, when it dehumidifies and releases moisture.

The Control of the Paper Quality

  • The surface of the paper is controlled under the light coming from one side by examining visually and touching with hands.
  • The paper should be examined with loop by lightening from above and below to understand its cleanness.
  • The firmness of the paper is understood by folding it repeatedly and tearing widthwise and lengthwise.
  • The thickness of the paper is understood by measuring with micrometer.
  • The whiteness of the paper may be measure by using measuring devices.

Whether the amount of glue in the paper is high or low is possible to understand by drawing lines on the paper with pen widthwise and lengthwise. If the ink doesn’t spread on the paper and does not pass behind, we can say that the paper is fully glued. If the thin lines do not spread and do not passes behind, but the thick lines spreads and passes behind, this paper is half-glued. If both lines passes behind, we can interpret that it is hardly glued or there is no glue in this paper.

  • We understand whether a paper is air-permeable or not by lighting a candle under it. The paper is not air-permeable releases many air bubbles when a candle is lit under it.
  • The light transmission of the paper is understood when something printed has been put under it and examined.
  • Whether the paper is dusty or not is very important. Because it damages the rollers of the machine, the paper gets tested by wiping with a black cloth or the paper being tested gets wiped on a black paper to see whether its dusty or not.
  • One side of the paper is moistened to understand the absorbance of the paper. The absorbent paper draws the water quickly.
  • The surface of the paper is pressed with a wet finger and the finger is pulled immediately to understand whether the paper makes picking during printing.

Paper Sizes

Because the paper used in the rotation printing are sold in bobbins, they are ordered with the width of the bobbin (For example, 70 gram, High Grade, bobbin in 45 pieces). In the machine making layer printing, the paper is cut in layers and sold in rolls or packages.

Besides that, there are papers in any sizes, if required; paper in desired sizes may be obtained by making special cut from the papers in bobbin.

Calculation of the Paper Weight

The weight of a paper of 115 grams and 70x100 cm

70 cm x100 cm = 7000 cm2

Because 1 m2 is 115 g, 7000cm2/10000=0,7 m2

115 gr x 0,7 m2= 80,5 gr.

the paper in this measure is 80,5 g, a roll of paper in 500 layers in the weight of 80,5gr x 500 pieces = 40,250 kg

In other words, the formula to be applied to find how many kg a roll of paper is; The weight of one layer of paper = (the width of paper x length x basis weight) / 10.000

Paper Sizes
A0 - 841 mm x 1189 mm B0 - 1000 mm x 1414 mm C0 - 917 mm x 1297 mm
A1 - 594 mm x 841 mm B1 - 707 mm x 1000 mm C1 - 648 mm x 917 mm
A2 - 420 mm x 594 mm B2 - 500 mm x 707 mm C2 - 458 mm x 648 mm
A3 - 297 mm x 420 mm B3 - 350 mm x 500 mm C3 - 324 mm x 458 mm
A4 - 210 mm x 297 mm B4 - 250 mm x 350 mm C4 - 229 mm x 324 mm
A5 - 148 mm x 210 mm B5 - 176 mm x 250 mm C5 - 162 mm x 229 mm