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).
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.
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
“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
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
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
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
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.
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.
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 . According to other sources , 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
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
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
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
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
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
polystyrene pigments and others
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
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
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,
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).
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
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.
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
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
- 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.
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.
uniform paper along with long ones
some fibers present
number of small fibers, mainly
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
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
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.
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.
called machine smooth paper,
matte or unglazed (uncalendered).
Paper additionally passed through
supercalender, called glazed,
calendered or polished.
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.
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).