Density, bulk, whiteness – the main characteristics of paper
The number of types and grades of paper in the modern world is enormous.
The following types of paper are most often used in printing:
– book and magazine;
– packaging waste cardboard;
– designer paper and cardboard.
A special type of offset paper is used for copying and printing equipment. Depending on the type of printing (laser or inkjet, color or black and white, low or high speed printing, etc.), you need to use the appropriate paper to get a high-quality print and not damage the equipment.
Special papers for color laser printing are becoming increasingly popular due to the development of digital printing.
Main characteristics of paper: density, bulk, whiteness
Additional characteristics: hardness, smoothness, opacity, tensile strength and many others.
measured in grams per square meter. So, for example, an A4 sheet is one sixteenth of a square meter, so with a density of 80 g/m2 it will weigh 5 grams.
To find out how many sheets of a particular paper are in 1 kg, you need to divide 1 by the weight of one sheet. So in 1 kg of paper with a density of 80 g/m2 there are 200 sheets of A4 (1 / 0.005).
Knowing the cost of paper per kg (ton), you can calculate the cost of one sheet using the table below. And vice versa.
Why is paper density not measured in grams per cubic centimeter? The fact is that the density of paper in g/cm3 is close to 1 (the density of water). Therefore, the density indicator in g/m2 is very close to the thickness of the paper sheet, expressed in microns. In fact, when we talk about density, we mean the thickness of the paper. You need to know the thickness of the paper to be sure that it will fit into a particular printing equipment. You also need to know the density to calculate the cost. By introducing the density indicator per square meter, we killed two birds with one stone: one indicator is used both to calculate the cost and to characterize the thickness.
This was the case before, but technology is improving, and manufacturers have learned to make both very loose paper and very thick paper.
It was necessary to introduce one more characteristic – plumpness
. Plumpness is measured in cubic centimeters divided by grams (this is simply the reciprocal of bulk density, which is what you learn in school).
If the bulk density of paper is less than one (lighter than water), its bulk is greater than one, and the numerical value of the thickness in microns is greater than the numerical value of the density in g/m2.
For example, offset and xerox papers with a density of 80 g/m2 have a bulk density close to 1.25. Multiplying 80 by 1.25, we get a sheet thickness of approximately 100 microns. A pack of 500 sheets will have a thickness of 50,000 microns = 50 mm = 5 cm.
Coated papers, on the contrary, have a bulk density of less than one (heavier than water).
How to use it? The price range for paper is very wide. If we talk about the final product, then, from the consumer’s point of view, plumpness and rigidity are important, not density. This makes it possible to replace one type of paper with another in order to reduce the cost of the final product. For example, we will replace paper No. 1 with paper No. 2. Let the bulk of paper No. 2 be 30% more, and the price per kilogram be 15% more. Then we will get a saving of approximately 15%! The effect of using plump papers is especially noticeable in book production, because… The weight of the circulation can be measured in hundreds of kilograms and tons.
Sometimes the reverse replacement is also possible. For example, for laser printing, you can replace paper and reduce bulk by 30% and price by 60%.
paper depends on how contrasting the image printed on it will look and how accurately the colors will be reproduced.
There is an ISO standard for brightness that determines what percentage of light will be reflected when paper is illuminated with light at a wavelength of 457 nm. However, the subjective perception of whiteness by the human eye depends not only on the amount of reflected light, but also on its quality. Perception is affected by the roughness of the surface, the shade of white paper (bluish, yellowish), as well as the presence of optical brighteners in the paper, which, absorbing ultraviolet light, re-emit in the visible spectrum. The CIE whiteness index is closest to human perception and can take values greater than 100%. This indicator is measured in natural sunlight (or close to it, but necessarily containing ultraviolet rays in its spectrum).
– this is an indicator of how much the paper itself prevents the transmission of the printed image applied from the back side of the sheet to its front side. This indicator is especially important for double-sided copying, when printing is applied on both sides of a sheet of paper.
– this is a characteristic of the mirror reflection of the light incident on it by the surface of the paper. Highly glossy papers have a rate of 75-80%, and matte papers – up to 30%. And, although most consumers of printed products prefer glossy papers, they are not always needed in publications. Thus, when reproducing text or line illustrations, paper with minimal gloss is used, and various brochures, labels, and reproductions of paintings are perfectly produced on high-gloss paper.
Humidity is a very important indicator for laser printing. Typically, office papers are produced with a lower moisture content (4.2 to 4.5%) than offset paper (5.0 to 5.5%). The reason is that office papers are exposed to significant heat in almost all models of copiers. When humidity is low, paper is less exposed to temperature changes and, as a result, is less likely to curl or wrinkle during the transfer process.
GOST for thermal paper was introduced – komus wholesale own production
On August 1, 2022, the national standard of the Russian Federation was put into effect GOST R 58079-2022
“ Heat-sensitive paper
for printing devices. General technical specifications
” By order of the Federal Agency for Technical Regulation and Metrology of February 8, 2022 N 60-Art.
Key requirements for thermal paper
according to the new standard are presented in the following table:
|No.||Indicator name||Paper allowance||Test method|
|1||Nominal weight of paper with an area of 1 m2, g||45-70||According to GOST R ISO 536|
|2||Permissible deviations in mass 1m2, g, no more||5.0|
|3||Thickness, mm||0.055-0.075||According to GOST R ISO 534|
|4||Permissible deviations in thickness, mm, no more||0.005|
|5||Breaking force in the machine direction, N, not less||40||According to GOST R ISO 1924-2|
|6||Smoothness on the coating side, s, not less||200||According to GOST 12795|
|7||Whiteness on the coating side, %, not less||80||According to GOST R ISO 11475|
|8||Optical density of thermal imprint, not less than||1.0||According to GOST 30116|
|10||Humidity, %||5±1||According to GOST ISO 287|
Our company uses only imported raw materials in production
of the highest class, which allows our partners to be confident that all thermal paper products
, purchased from us, will meet all the requirements of the new national standard!
US Paper Weight
Determining paper density by the weight of the paper package was previously widely used in the UK, Europe, as well as in North America, where it is still used. The popularity of the method in Europe fell after the international standardization of paper sizes under ISO 216 and its national predecessors in European countries.
Weight is defined as the weight of a ream of uncut paper in pounds (lb) (Note: Reams of paper are often written # after the weight number instead of pounds). There are many types of uncut paper that are used in various industries: for office paper and cardboard, Bond, Cover and Index are used.
So if you have a sheet of 20lb Bond Letter, it will be the same thickness as 20lb Bond Legal, although the sheets will weigh differently. But a sheet of 28lb Bond Letter sized paper will not be the same size as a 28lb Cover Letter sized paper since the uncut Bond and Cover sheets are different.
Paper that is most often used in offices has a weight of 20-24 pounds (lb). Often suppliers will omit the word Bond on the packaging and simply list the weight as 20 lbs or 24 lbs, since other packaging formats always write Index or Cover unless the default Bond type has been used.
Newsprint has its own type, Newsprint, which measures 24″ x 36″ in uncut sheet size. This is significantly thicker than the untrimmed Bond and Cover types, so the most common 30lb Newsprint is actually significantly thinner than the 20lb Bond type. The next page talks about the different types of stock types of uncut sheets of paper.
Tables for converting paper weight from g/m2 to lb and vice versa.
Density grams per square meter (gsm)
ISO 536 paper weight is generally indicated on product packaging in g/m2 or GSM. This standard defines the weight of one sheet of A0 paper (which has an area of 1m2) depending on the specific gravity. This means that an A0 sheet of 80 g/m2 paper will weigh 80 grams, an A0 sheet of 100 g/m2 paper will weigh 100 grams, and so on.
Note: the packs are usually written GSM, not g/m2 in most companies. This was due to the inability of early computer packages to display superscript characters—a feature of inventory, accounting, and billing systems.
Paper commonly used in offices typically has a weight between 70gsm and 80gsm, with 80gsm being the most commonly found weight. Some accountants and lawyers use thicker paper, ranging from 90gsm to 120gsm for formal correspondence.
See this page for a chart of individual sheet weights of 4A0, 2A0, A0, A1, A2, A3, A4, A5, A6, A7, A8, A9 and A10 for various commonly used paper weights.
Calculation of package thickness
The main characteristics of bags (packaging, “T-shirt”, with loop, cut-out handles) are the height (h), width (b) and thickness of the bag (t bag).
The height and width are determined using a measuring device – a ruler. Determining the thickness is much more difficult, because Packing density is not measured in micrometers; this indicator varies in different places.
The average thickness of the package is determined indirectly, using the formula. To do this, it is enough to know the dimensions of the package, the specific density of the film and the weight of the package.
Width and height are determined using a regular ruler; specific gravity is taken from a reference book. For example, the average density of LDPE is 0.92 g/cm3, HDPE – 0.96 g/cm3.
The weight of one package is determined by weighing the package, the resulting result is divided by the number of packages.
Let’s calculate the packet density:
From this formula it follows that the thickness of the package is the ratio of the mass of the package (m) to its product of density and area (ρ × h × b):
After determining the thickness of the bag, you can find out the thickness of the film (tfilm) from which the bag is made. The thickness of the film is equal to half the thickness of the package, measured in centimeters.
To convert it into the usual micrometers, or in other words microns (µm), you need to multiply the result by 10000.
Example. HDPE packaging is 25x40cm, a package of 1000 bags weighs 2 kg. How to find the average film thickness:
The given formula is used for food packaging, garbage bags, HDPE and LDPE, with or without handles. When calculating the film thickness for a T-shirt package, the result is multiplied by a correction factor of 0.8 (approximate value).
- Using micrometer
– a device for measuring with an accuracy of plus or minus two microns. Because polyethylene film stretches, the error of such measurement is at least 10%;
- Determination of roll weight using high-precision weighing equipment. This method is used for production control. Carrying out such a measurement guarantees high accuracy, because Together with the area, this indicator directly affects the weight of the product.
|Name||Size, cm||Film thickness, µm||Weight, g||Packing|
|HDPE||70×110||11||16||rolls of 30-60 pieces|
|PVD||70×110||30||43||rolls or sheets 30-50 pieces, sheets 250 pieces|
|HDPE with ties||75×90||15||22.3||rolls|
|LDPE with ties||70×105||30||42.1|
Plastic card thickness
The process of creating a double-sided plastic card consists of sintering four different layers: a transparent laminate layer (0.08 mm thick), plastic (0.3 mm thick), plastic (0.3 mm thick), a transparent laminate layer (thickness 0.08 mm).
The total thickness of the card is 0.76 mm. Thus, the image is under a layer of laminate and is reliably protected from mechanical damage and paint abrasion. With our technology, printed personalization is also located under the laminate layer.
Thicknesses and formats of plastic sheets used for printing in our printing house
Plastic sheet thicknesses available for laser printing: 90 microns, 125 microns, 200 microns, 275 microns, 300 microns, 350 microns. The main size of sheet plastic is 320*450 mm.
For most plastic sheets, the option of double-sided lamination with matte and glossy films with a thickness of 32 microns, 75 microns, 125 microns is available. Accordingly, double-sided lamination can add to the sheet thickness: 64 microns, 150 microns, 250 microns. Thus, when laminating 350 micron plastic with a 125 micron film, you can obtain products with a thickness of 600 microns or 0.6 mm.
Thicknesses of coated papers
Below is a table indicating the approximate thicknesses of coated papers from European manufacturers
|Paper weight||Glossy papers||Matte papers|
|90 g/sq.m||0.06 mm||0.065 mm|
|115 g/sq.m||0.08 mm||0.09 mm|
|130 g/sq.m||0.09 mm||0.11 mm|
|150 g/sq.m||0.105 mm||0.125 mm|
|170 g/sq.m||0.12 mm||0.14 mm|
|200 g/sq.m||0.17 mm||0.185 mm|
|250 g/sq.m||0.185 mm||0.225 mm|
|300 g/sq.m||0.22 mm||0.31 mm|