The history of paper. | Useful article about paper – Snow Maiden.

Paper smoothness

The smoothness of paper is one of its most important printing properties, which depends on

microgeometry of the paper surface, that is, from the relief formed by protrusions

and depressions between plant fibers and filler particles. Microgeometry

papers are controlled by profilographs, microinterferometers of various systems,

drawing a profilogram of its surface (Fig. 1).

Surface good

glazed coated paper has mostly

micro-roughness within 0.1-0.5 microns,

superglazed high smooth

coated paper – 0.03-0.05 microns.

This paper has no roughness.

The glossiness and dullness of paper also depend on the microgeometry of its surface.

Very smooth papers will be glossy, rough papers will be matte (Fig.

2).

Mostly effective smoothness

paper is determined by its microrelief, so

how macro-irregularities are suppressed in the process

printing. This, of course, does not apply to rude ones

mechanical inclusions that are not

are smoothed during printing even in the case of

very strong printing pressure. Therefore

Increased contamination of paper is not allowed.

Smoothness (roughness) is a very important factor on which printed materials depend

properties of paper. At the same time, this is a rather difficult indicator to determine for paper

(Fig. 3).

GOST 12795.-89

“Paper and cardboard. Determination method

Beck smoothness” corresponds to the standard

ISO 5627-84. Results obtained from this

method, comparable to the results

determining paper roughness using

Bendtsen instrument ISO 2494-74.

Abroad, smoothness (roughness) indicator

determined by devices supplying flow

air at constant pressure, while

Bendtsen, Schaeffer,
devices are used

Parker. Therefore, when determining any

indicators need analysis

comparability of methods and means

quality control of printed types of paper by

GOST and ISO.

In the printing industry

paper going through various technological processes

processes, experiences various kinds

impact and deformation. So, at

Letterpress printing presses on paper in relief

printing elements of the form, in bookbinding

in production, paper is folded into a notebook

and pressed.

Material property instantly

change its shape and size to

under the action of an appropriate load, and after

termination of its effect is also instantaneous

restore original shape and size

called elasticity. Therefore,

elastic deformations are instantaneous

emergent and fully reversible

deformation. According to the law

Hooke they are directly proportional

applied voltage.

Elasticity – property

material to change shape and size under

under load for some time

period of time and gradually

completely restore the original

shape and size after termination

actions. Elastic deformations

appear gradually, following elastic ones

deformations, and also gradually

disappear after termination

corresponding voltage.

The property of a material to retain the resulting deformation after mechanical removal

the influence that causes it is called plasticity. Therefore, elastic-elastic

deformations are completely reversible, and plastic ones are residual (Fig.

3).

In printing they are necessary as elastic-elastic,

and plastic (residual)

deformation. Elastic properties

have a positive effect on the process

printing, but often there are

insufficient for proper

paper surface leveling and compensation

irregularities as a printing plate (offset

canvas) and the paper itself.

Plastic deformation of paper

technologically necessary for folding,

creasing, shading, embossing. Such

conflicting requirements for properties

papers are not satisfied by

compromise, but through creation

its various types and varieties.

The elastic-elastic properties of paper largely depend on humidity and degree

compaction, calendering of paper and the force applied to it. Must have

keeping in mind that it is not possible to significantly increase the elastic-elastic properties of paper

possible, but for stitching and binding work this is completely undesirable.

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at the same time, the problem of increasing plasticity is easily solved. Thus, paper containing

wood pulp with relatively shortened, not too fibrillated (tattered)

cellulose fibers (Fig. 4), as well as a significant amount

filler and especially moisture, will be plastic.

Equipment and technology

For mechanical processing of fibers, a pounding or hammer mill was initially used. A water wheel and sometimes a horse saddle were used to drive the mill. The crushing made it possible to obtain better development of fibers compared to the stone millstone mill used by the Arabs.

In the 13th century, paper production began in Italy, although at least a century before that it had been brought into the country by traders.

This is a situation where paper has been used in the country for many years, but was not produced characteristically for Europe. Between the time the use of paper began and the time the country began producing its own paper, 100–300 years passed.

  Nowadays, more than half of the countries do not produce paper, buying it from other 109 countries that produce paper and cardboard.  

The influence of the Italians on the development of paper production turned out to be very productive. The Arabs used wheat (possibly also rice) starch for sizing paper, the Italians began to use animal glue, which made it possible to obtain a new quality (wear resistance, barrier to water).

In Italy, for the first time, they began to use a crusher driven by a water wheel to grind raw materials. Here the requirements for paper were formulated, the prototype of the standards, for the formats produced, the use of watermarks, quality, number of sheets in reams, and fines.

The Italians were the first to use a watermark. Paper with a watermark dated 1282 was found in Bologna [2]. According to other sources [3], the first described watermark was obtained in 1271 on paper made at the Fabriano paper mill.

Here we note that the first watermarks were light in relation to the field of the paper. In the place of the watermark, the wire (filigree) used to obtain it created thinner places in the paper that looked white when held up to light.

  In 1818 in Russia, at the paper mill of the State Paper Procurement Expedition (now Goznak), a watermark with variable optical density (multi-tone) was first obtained. This was achieved by stamping a mesh on which the paper was cast to obtain a multi-level relief on the mesh.  

Italians, and after them other Europeans, for a long time believed that paper was invented in Italy, in the town of Fabriano. In the Middle Ages, about 40 paper manufacturing enterprises operated in Fabriano.

And although by the 15th century paper production had been mastered in most European countries, Italian paper still dominated the European market.

As a result of technical and technological innovations, French, English and Dutch paper became in great demand by the 17th century. This was largely facilitated by the appearance in Holland of a grinding device – a hollander (later it began to be called a roll). The Germans delayed the introduction of rolls in their mills – as a result, they lost in paper quality.

Paper making technology

Milled cellulose fiber,

wood pulp, bleached and ground

kaolin, glue, tint are mixed as needed

proportions. This mixture is called paper

mass.

When producing many types of paper

and cardboard to increase whiteness,

opacity, smoothness, enhancement

printing and other properties in fibrous

fillers are introduced into the mass, that is, chemically

inert minerals, less

hydrophilic than cellulose fibers.

Filler particles filling

large pores of paper, separate the fiber,

increasing the overall porosity of the paper

leaf. Formation of numerous small ones

pores with capillary properties

increases paper’s ability to

perception of printing ink.

Fillers, distributed in small

pores between the fibers of the resulting paper,

increase porosity and increase

breathability. They also

help reduce linear deformation

when moistened and reduced

paper curl when single-sided

wetting.

The degree of influence of one or another

filler on paper properties depends on

its type and quantity in paper.

Fillers must be homogeneous and finely dispersed,

provide maximum opacity,

adheres well to the fiber. Particles

filler must have high

refractive index of light flux,

equal to approximately half the length of the visible

spectrum

As a printed filler

paper mainly uses kaolin –

white porcelain clay or talc –

compound from the class of silicates. Dioxide

titanium is used in production

coated papers. During production

special types of paper as filler

zinc oxide is used.

For each type of paper there is

certain optimal quantity

filler. Each filler has

specific features as in plan

influence on the properties of paper, both in terms of

adhesion in the structure of a paper sheet with plants

fibers.

Particle adhesion mechanism

filler depends on the shape and size

particles (their optimal size is no more than

0.3 µm). Shape and size of powder particles

also affect whiteness, gloss, smoothness,

absorbency of paper or cardboard

printing inks and varnishes.

Paper and cardboard with high

filler content represent

a kind of imitation of coated

material. Depending on dispersion

filler increases the density of paper and cardboard,

thickness decreases accordingly

material.

About the quantity contained in the paper

The filler is judged by its ash content. Contents

ash in paper corresponds to approximate

content of inorganic substances, but not

determines the quantity of each of them separately.

By mineral content

filler all types of paper conditionally

are divided into several classes:

• paper with natural

  ash content, without mineral filler;

• low ash paper,

  with ash content up to 5%;

• medium paper

  ash content, with ash content up to 15%;

• paper with increased

  ash content, with an ash content of more than 15%;

• high ash paper,

  with an ash content of more than 25%.

As already noted, as

fillers most commonly used

the following materials: chalk, kaolin, talc,

Barium and calcium sulfates, dioxide

titanium, various aluminosilicates, pigments

based on urea-formaldehyde

concentrate, microcapsules

polystyrene pigments and others

substances.

Kaolin (white clay) –

aluminosilicic acid, white powder

hexagonal colors, medium size

particles about 2 microns, whiteness 70-90%, coefficient

refraction 1.56. Free ferruginous

minerals present in kaolin,

give it shades from light yellow to

red-brown. For optical properties

kaolin impact titanium

minerals.

Talc – sour salt

metasilicic acid. White Powder

color, plate, needle or

scaly shape, particle size 2-10 microns,

whiteness 70-80%, refractive index 1.57.

Talc gives paper softness, noiselessness,

gloss, increases adsorption of printing inks and varnishes.

At the same time, talc promotes

increasing paper dustiness, reducing

effect of optical brighteners.

Blankfist – sulphate

barium. Commodity blankfist has

pasty appearance, degree of dispersion

0.4-0.6 microns, whiteness 96%, coefficient

refraction 1.64, holds well in paper.

Blankfist increases paper whiteness, decreases

transparency, gives paper shine,

sonority and hardness to the touch,

used for high-grade species

paper.

Gypsum – class mineral

sulfates, white powder. Burnt

state, particle size decreases and whiteness

gypsum increases. Average particle size

burnt gypsum about 5 microns, whiteness

85-96%, refractive index 1.57. Natural

gypsum gives paper ringing and rigidity

to the touch.

Titanium pigments –

titanium dioxide or combination with sulfate

barium White powder, particle size

0.3-0.5 microns, whiteness 95-98%, coefficient

refraction 2.55. Titanium pigments impart

paper with a high degree of opacity.

Chalk – natural or

chemically precipitated calcium carbonate,

white solid,

insoluble in water, soluble in weak

acid. Average particle size of precipitated particles

chalk 0.2-0.4 microns, density 2.-2.9 g/m3,

whiteness 80-95%, refractive index 1.48-1.68.

Chalk gives paper softness and whiteness,

opacity, increases absorbency

printing inks and varnishes. In production

most often used not as a filler,

and as a pigment for enhancing paper with

with the goal of getting good from it

visual perception of printed matter

images (paper coating).

Coated

paper, matte or glossy, consists of

base with a coating layer applied to it,

consisting of filler and binder. Goal

coating – creation on the surface

sheet of paper or cardboard, even, smooth

and at the same time an elastic layer with

uniform lumen.

Coated layer

promotes quick fixation of paint and varnishes,

and also improves visual quality

imprint. The coated layer should be

chemically neutral, since excess

alkali or acid may change during the process

printing color characteristics of paint on

piece of paper.

Fillers

significantly affect the properties of paper.

Thanks to them, after calendering paper

becomes even, smooth, opaque,

plastic, capillary and less porous.

All this is especially important for papers,

used in high and deep

print.

If the paper is made of white

wood pulp and unbleached pulp,

the filler increases the degree of whiteness.

However, fillers slightly reduce

mechanical strength of paper, since

limit the occurrence of hydrogen

bonds between cellulose fibers.

When soaked in water regular

paper grades lose their mechanical properties

strength, when impregnated with kerosene or

Oils hardly change the strength of paper.

This suggests that cellulose

fibers in paper are connected to each other

mainly by hydrogen bonds and to a lesser extent

degrees – by van der Waals forces and friction.

Paper is cast on

paper machines consisting of

four parts:

• grid;
• press;
• drying;
• finishing, rolled

  (winding into rolls).

These machines usually have a flat mesh conveyor. They

operate at speeds up to 800 m/min with mesh widths up to 7-8 m.

Paper

the mass flows onto the mesh

paper machine. Formed from

mushy mass thin fibrous layer

gradually freed from water at

mesh part. On the press part of the machine

the water is squeezed out by the pressure of the press, and in the dryer

pieces of paper tape pressing against the dryer

cylinders, brought to 95% dryness.

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uniform paper along with long ones

some fibers present

number of small fibers, mainly

hardwoods that

fill the free space between

long fibers. Thus

the total area on which

strong ones are installed between the fibers

connections, which contributes to an increase

mechanical strength of paper.

In the drying part there is

size press

There are several technologies

sizing paper pulp. Offset,

cartographic, phototype, cover,

writing, drawing and some

other types of paper are sized in mass

various substances such as

rosin glue, starch, urea

resins, organosilicon polymers, etc.

Sizing in the mass makes the paper more

moisture resistant, making it difficult to penetrate

water, but without interfering with the absorption of oil

printing inks. This is especially important

for papers used in flat (offset)

printing, lithography and phototypes, where at

seals are used and moisturizing with water

solution.

Surface sizing of paper

most often carried out with 3% aqueous

carboxymethylcellulose solution, which is not

only increases the moisture resistance of paper, but also increases

the strength of its surface, which is especially

important when working with viscous and sticky materials

paints and water-dispersion varnishes.

Finishing part

Paper Making Machine Presented

machine calender consisting of three to eight

polished cast iron cylinders, which

with their weight they compact the paper, making it

the surface is smoother.

Calendered paper

called machine smooth paper,

matte or unglazed (uncalendered).

Paper additionally passed through

supercalender, called glazed,

calendered or polished.

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fiber paper making process,

carried away by the flow of paper pulp,

predominantly take the position at

in which their axes coincide with the direction

movement of the mesh of the paper making machine.

Therefore, the properties of a paper sheet in longitudinal

(in the direction of movement of the grid) and transverse

directions will be slightly different, namely:

the strength of the paper will be higher in the longitudinal direction

direction, and the change is linear

size when moistened will be significant

more in the transverse direction.

Except

In addition, the top (front) side of the paper, not

in contact with the mesh

paper machine, will be much

smoother than mesh. The mesh side has

less filler partially leaking out

paper along with rinsing waters.

Therefore, the paper is orthotropic, that is

its properties vary somewhat in all

three dimensions (width/length and face/back).

All this must be taken into account when

preparing paper for printing, especially

to multi-color, and during processing

prints in bookbinding and bookbinding

finishing shops (for cutting, folding,

sewing, die cutting and embossing).