Coated paper – stages of production, scope, types, quality characteristics, properties and price

The content of the article

• What is coated paper
• What is it used for?
• Chemical composition
• The main stages of production
• Pulp application on a paper machine grid
• Machine or surface sizing
• Calendaring basics
• Final calendering
• Paper coating
• Types of coated paper
• Qualitative characteristics and properties
• Roughness (smoothness)
• Porosity
• White
• Opacity
• Gloss
• Light transmission
• Humidity
• Printing on coated paper – process features
• Magazines and brochures
• Books and colorful albums
• Posters and calendars
• Business cards and notebooks
• Where to buy coated paper
• Production in Russia
• How much is
• Advantages and disadvantages

For the manufacture of glossy magazines, posters, art albums and all kinds of printing, today several slightly different materials are used. One of them is coated paper, which can have a matte or glossy coating of different weights. It is also called design, because with the help of such paper you can get really high-quality products with a bright photo.

What is coated paper

This type of paper is a high-quality base, which is widely used for the manufacture of materials for which a pleasant appearance and brightness of colors, such as presentation catalogs, booklets, are important. Due to the fact that it is pleasant to the touch and, using it, you can get clear prints, such products are in great demand. Get it when applied to the base in the form of ordinary paper one or more layers of coating, which includes kaolin, chalk and binders. Weight varies from 60 to 250 g / m2.

What is it used for?

The main difference between coated paper or simply chalk, which is widely used in the Russian printing house and not only, from other varieties is the structure. The coating layers on which the base is coated include adhesives and white pigments. Moreover, for a glossy and matte surface, even with the same density, different paints are needed. This is due to the fact that drying on glossy material occurs faster than on matte due to the fact that its pores absorb better. This kind of paper is used for the manufacture of:

• posters;
• color stickers with advertising, illustration;
• various large-format calendars;
• expensive children’s publications;
• art albums;
• promotional products of high quality;
• mass-produced magazine products;
• inserts for various consumer goods;
• other types of printed products where you need to achieve high quality.

Chemical composition

Paper chalk for inkjet printing has a pulp in its composition, which acts as the basis and a number of specific fillers that contribute to the formation of the coating. One of them is titanium dioxide, which is considered the best and highest quality, but it is expensive. Of the more economical supplements, kaolin has become the most common..

The main stages of production

Before you get chalk, get acquainted with the technological process of its production. For this, manufacturers use modern paper machines. First of all, the pulp is applied to a rapidly moving mesh, after which surface or machine sizing is carried out, which is necessary to reduce the degree of absorption of the binders. Next is the calendering of the base, during which the canvas is pressed and dried. Cretaceous gains basic surface properties by means of final calendering.

Pulp application on a paper machine grid

Initially, the mixture consists of 5-7% wood pulp and 93-95% water. Water as it passes through the machine is removed, as a result of which a paper web is formed, which, in this case, has the front and mesh sides of the sheet. On the most modern paper-making devices, a double-mesh type web formation system is used. The pulp in this case is fed between two nets, after which vacuum drying is applied to it. In this regard, the grid side of such coated products is practically no different from the front.

Machine or surface sizing

Paper sizing is carried out in bulk or at the finishing stage. This procedure is necessary in order to reduce the absorption of binder printing inks. In this case, by machine sizing is meant the procedure for introducing sizing agents directly into the pulp. If the sizing procedure is carried out at the last stage of the production of chalk, then it is called surfaces. This type of sizing is carried out using size presses.

After the procedure, the probability of plucking the fibers during printing is significantly reduced. For sizing, rosin, its derivatives and some other substances are used. Recently, chemically neutral additives of a synthetic type have begun to find wider application. Cretaceous, the composition of which was supplemented with such additives is called neutral sizing paper..

Calendaring basics

As for the calendering of the base paper, the quality of the finished product, such as opacity and puffiness, depends on its degree. The work of calendars, which are heated rotating metal shafts, consists in pressing the web, drying it and making it smooth. The more the resulting fabric is compressed, the less puffy and more transparent it will turn out. For the production of high quality coated paper, it is very important to balance the opacity and smoothness of the substrate..

Final calendering

This stage is necessary in order for the finished product to acquire its basic surface properties, for which it is so appreciated in the printing field. This process is practically no different from calendaring the base. The difference lies only in the set of shafts, which differ depending on the surface of the coating – glossy or matte. Many modern factories have calendars with adjustable clamping forces for each shaft. In addition, all shafts are covered with plastic, which makes the calendering process more gentle.

Paper coating

Coverage of the coating is single or multiple. The double coating, as a rule, is made of a layer that is applied to a paper-making device and to a separate coating unit. There are machines in which double coating is carried out using a sequential double coating. The second layer can be applied to a wet base or to a dried one. With three or more multiple coatings, the application of the first layer is carried out only on a damp base. Types of coating:

• Machine. With this coating method, the first layer applied inside the machine is insignificant in mass (about 4 g / m2), and the second is much more significant (2040 g / m2). This method is not used for all types of paper, in addition, it has difficulty stopping and disconnecting individual sections when problems arise with a coating device or paper machine.
• Scraper. The excess mixture in this method is removed using a flexible knife called a scraper or air jet..
• Cast. The mixture layer in this case is sprayed using a series of nozzles, which ensures a more uniform application. This process is expensive, so it is used more in the production of designer and some label products..
• Curtain. This method is considered very promising. For its implementation in the device there are no mechanical elements that are designed to equalize the mass (paste) on the surface of the canvas. The paste falls onto the canvas in the form of a curtain under the influence of gravity. At the point of contact with the main curtain, it begins to change the direction of movement, as a result of which it stretches, forming a thin film. The disadvantage of this method is that the paste is applied only on one side of the base, but the uniformity of the thickness of the layer does not depend on the roughness of the canvas.

Types of coated paper

As a result, after production, a product is obtained that consists of pulp subjected to processing and forming a paper base, and a number of fillers and binders that make up the coated coating. Before ordering this type of paper for offset printing or manufacturing representative products and highly artistic publications, familiarize yourself with its types. More on classification:

• Matte and glossy chalk paper are distinguished by surface finish. The first is characterized by better touch perception and greater rigidity. In addition, compared with a glossy analogue, it has greater opacity and puffiness, the ability to better reproduce text information. Coated glossy paper is more smooth, better printed results, minimal dusting and curing. It is often used for glossy publications, moreover, its use reduces paint consumption. There is also a kind of intermediate surface finish called semi-matt or silk and satin.
• By the nature of the pulp (cellulose content), cellulose coated products are isolated, the wood pulp content of which is not more than 10%, and paper, where this parameter reaches 25%. The latter have a greater degree of opacity and smoothness, but less whiteness and gloss..
• By weight of the highlighted sheet. Depending on this characteristic, there can be a base of high density (over 150 g / m2), medium (70-150 g / m2) and light (up to 60 g / m2).
• Depending on the number of coated sides, sheets with single and double coating are distinguished. The former are more commonly used for the manufacture of labels..
• The format is roll and sheet coating. Most coated paper comes in sheets that are packaged in bundles. Thanks to such packaging, the products are maximally protected from negative external influences during transportation and storage. Nevertheless, part of the chalk is delivered to the market in rolls. This option is mainly intended for rotary offset printing with hot drying or gravure printing..
• There is still a classification according to the number of coating layers. Depending on this characteristic, single-, double- and three-layer products are distinguished. Increasing the number of layers improves smoothness and whiteness.

Qualitative characteristics and properties

The degree of finish of coated sheets directly affects the quality characteristics of the final product. Modern manufacturers deliver to the market chalk in a wide assortment, which is suitable for the production of a variety of printed products. You can get a really clear print and a colorful layer, provided that you choose the right brand. To do this, take into account such characteristics and properties as:

• roughness (smoothness);
• porosity;
• white;
• opacity;
• gloss;
• light transmission;
• humidity.

Roughness (smoothness)

This parameter refers to the average height of the microroughness of the coated sheet, which is measured in microns. For chalking, the surface roughness (smoothness) is about 0.83 microns – this is an order of magnitude smaller than the raster dot reproduced by offset printing. A smoother coated sheet helps reduce ink consumption and improve image quality. The most accurate indicators are provided by the Bendsten method, when the chalk is pressed with a glass (thin-walled), after which the volume of air in mm, measured in 1 min, is measured.

Porosity

An important printing property of coated paper is selective absorption, depending on porosity, which is about 30%. Under the influence of capillary pressure, micropores of the surface layer of the chalk absorb a low-viscosity paint solvent, and the film former and pigment in this case remain on the surface of the sheet. The pore size in most cases does not exceed 3 mm.

White

This parameter refers to how well the surface is able to reflect the light incident on it. The indicator is determined using at least 7 methods. In accordance with Russian GOST, whiteness is characterized by the reflection coefficient at a wavelength of 457 nm. This indicator corresponds to the concept of Brightness. The Russian method of measuring whiteness is valid exclusively for sheets without optical brightener. The second indicator is Whitness, which provides the ability to apply the full spectrum of visible radiation..

Opacity

This setting is considered especially important when duplex printing is required. To increase the opacity of the paper web, manufacturers select the composition of fibrous materials, combining the degree of grinding. In addition, to achieve a certain result, special fillers are introduced into the base and an appropriate degree of calendaring is selected.

Gloss

Under the gloss (gloss) is characterized by the ability of the chalk to reflect the light incident on it. On a sheet with a high degree of gloss and whiteness of the paint, the pictures look bright, but reading the text can be difficult. In the West, for printing publications with a large number of text materials, a matt surface is often preferred. In order to give the images additional gloss, in this case they can be selectively varnished or printed using glossy inks.

Light transmission

Often this characteristic is called opacity. Coated paper can have such a serious drawback as high light transmission, because Images on the back of the print become visible. To reduce the level of light transmission, fillers are introduced into the material that are specifically designed to increase light scattering, for example, titanium dioxide. The opacity of the coating with a density of 90–115 g / m2 can be in the range of 88–93%. The higher the density, the greater the opacity. At a density of 200 g / m2, it is 98.5–99.9%.

Humidity

Coated paper, which did not undergo prolonged acclimatization (up to 24 hours at significant temperature differences) in the printing workshop itself, can cause many printing problems. Equilibrium humidity with a relative humidity of 50-60% is about 56% with some deviations in one direction or another. For example, sheets with a high percentage of wood pulp in these conditions can have a moisture content of around 7%. Moistening of chalk over 6% in most cases leads to adhesion of sheets.

Printing on coated paper – process features

When preparing the original layout of the publication, the circulation of which will be carried out on a single or double coating of chalk, you need to take into account the total density of the colors. The limit value of the total paint overlay for this type of paper is an indicator of 320% – sometimes up to 360%. At the same time, more time is required for drying on a matte surface than on a glossy one, because the pores of the latter absorb better. The impression is protected from over-press and picking using a special powder, the layer of which separates the sheets in the foot.

Magazines and brochures

Coated paper is widely used for the preparation of magazines and advertising brochures. Due to the wide density range (from 90 g / m2 to 350 g / m2), chalk can be used to print almost any high-quality printing products. For printing magazines use both glossy and matte sheets. To give gloss on the cover, you can use a special varnish that can protect it from abrasion..

Books and colorful albums

Coated paper is often used to make hardback books and various colorful albums. With its help, you can achieve good quality text, especially if it will be sheets with a matte surface. Often, for printing, a base with a density of about 150 g / m2 is used, although some circulations are issued on paper-based 160-300 g / m2. In this case, the quality of the base to transmit fine and colorful elements without distortion depends on its smoothness.

Posters and calendars

You can use chalk to print relatively inexpensive but vibrant posters and calendars. The choice of a specific basis depends on the wishes of the client, the complexity of the order, circulation. The coated option is chosen if qualities such as maximum image clarity and color brightness come first. True, the cost of the final product when printing large runs will be an order of magnitude more expensive than when using an offset base.

Business cards and notebooks

The main purpose of business cards is to inform potential customers. Notebooks have an equally important role in conducting an advertising campaign. Confirm the high status of the organization can print business cards and notebooks on chalk. It is carried out on the basis of a density of 250-350 g / m2. If necessary, the front side is laminated. Production of business cards using coated backing provides high detail.

Where to buy coated paper

You can purchase such products for printing various types of printing in any specialized store, but in this case you may encounter a small assortment. To save money and order coated sheets of the required density and smoothness at wholesale prices, it is better to contact the manufacturers directly. This approach will help to purchase the required number of rolls or packs without intermediaries and as cheaply as possible..

Production in Russia

Coated paper is very popular in the domestic printing industry. Different types of chalk from various countries of the world enter the Russian market, for example, Germany, China, Finland, etc. It is known for certain that its production in Russia itself ceased in 2010, when only 4 tons of these products were produced. Prior to this, a number of enterprises were engaged in its production. In fact, output fell from year to year: from 2000 to 2009, production fell from 2000 tons to 942 tons.

How much is

The cost of such products can vary greatly depending on the country of production and quality characteristics. You can order suitable products for printing in any specialized store with delivery, but first, check out the price range:

Advantages and disadvantages

Chalk paper is considered the best in quality and one of the most popular. What kind of material is easy to understand by looking at several colorful magazines with clear text and photographs. The main advantages are:

• good quality;
• special smoothness;
• lower paint consumption;
• distinct print of text, photographs;
• long term use;
• selective absorption.

Coated paper has practically no negative sides, however, due to the glare of light it becomes more difficult to read the text and the eyes get tired faster. With regard to environmental friendliness, many experts consider all expensive and beautiful books with magazines dangerous to health. This is due to the fact that the purity and whiteness of their base is ensured by such a chemical component as dioxin.