The standard testing methods for raw materials in the printing industry mostly focus on the testing of paper inks. The International Institute of Printing Research literature workers have compiled the printing standards for fifteen countries and two organizations. The publication lists 88 standards or specifications for paper and other printing materials promulgated in Germany and 66 standards for inks and other related materials promulgated in Poland. Some standards are about adhesives and other bookbinding materials, and about photographic materials. But in general, the printing industry pays less attention to materials other than ink and paper.
A large number of detection methods, testing instruments, and inspection images can be evaluated by the printing factory for raw materials, which means that almost all paper or ink properties can be detected to comply with the established standards. The key question now is what testing methods should be used and how much testing should be done on various occasions.
When testing paper or other substrates, it is difficult to obtain a representative sample. It is very difficult for a stack of papers, especially large ones, to randomly sample from them without re-stacking them. For webs, the detection is not possible except for the (less representative) outer layer.
In general, the sampling of ink and photosensitive materials is not a problem. Another problem that should be considered when sampling raw materials is that some detection methods are destructive. Such as paper, cardboard strength testing, photosensitive material sensitivity testing, its samples will be damaged and consumed.
For the selection of a test method for a material, consideration should be given to the use of tests that can obtain data relating to defects in printed images or obstacles to print production.
The frequency of detection of a certain property must be based on the tolerance for the performance change, which in turn is related to the level of quality defects allowed by the final print. The more stringent the quality requirements of printed products, the more frequently the raw materials need to be inspected.
For most printing companies, it is impossible to spend as much time, money, material resources, and manpower on detecting raw materials as government departments or extra-large printing companies. The benefits of testing may not be enough to cover the cost of testing. However, this situation refers to a large-scale inspection, but in fact most printing companies can conduct small-scale inspections. All printing companies can properly invest in those tests that are cost-effective.
The following are the tests that control the factors affecting color reproduction:
1, paper detection
Some tests can be implemented with very simple devices.
(1) Thickness
To maintain proper printing pressure on the printer, use a caliper gauge. The thickness of the paper should also be measured with a micrometer. Usually ten sheets of paper are used to measure five points.
(2) Opacity
The opacity visual scale is an effective measurement tool. A set of characters is printed on a darkened background dot background, the paper under test is covered on it, and the character begins to look unclear somewhere on the scale, which indicates the opacity of the paper.
(3) Absorptivity
K&N ink is probably the most commonly used and cheapest test method. The ink is composed of a gray dye and an oil base, which is applied to a paper sample and is removed after two minutes. The remaining ash density is the absorbency of the paper.
(4) Gloss
The gloss meter was measured along the direction of the paper and the average was taken.
(5) Paper efficiency
This test combines the gloss and absorbency of the paper to determine the effect of the substrate on the ink film color. Absorptive but 100% gloss paper can print the most saturated colors. In contrast, 100% of absorptive but matte paper (such as newspapers) will print very poor colors.
(6) Color and lightness
The approximate properties of paper color and brightness can be obtained by measuring the density of red, green, and blue color filters after calibration using a reflection densitometer. Ideal paper, the density under each filter should be consistent, low density, indicating high lightness. The visual comparison method of paper samples is more meaningful for the detection of paper color and lightness.
(7) exposed leather
The Dennisson wax stick peel test, despite its shortcomings, is still a suitable method for determining the peel resistance of a particular substrate. The end of a certain grade of wax stick is melted and pressed against the substrate under test. After fifteen minutes, it is quickly pulled up and the exposed fiber or paint is inspected on the end face.
As with many other raw material tests, the relative significance of the wax stick test is greater than predictive. In other words, if the peeling does not occur, then when the paper whose peel strength is higher than 10 is printed under the same conditions, there will be no problem of peeling.
2, ink detection
The first step in evaluating the ink is to scrape the ink, preferably on the paper to be printed. It is usually operated with a wide knife, or a thicker ink layer can be rolled out with a small ink roller. When comparing two inks, it is generally required to scrape two ink samples on the same piece of paper in parallel. There is often an on-site ink bar in the middle of the squeegee.
(1) Opaqueness
Some inks, such as yellow ink, are not as transparent as other inks. In the case of color printing or overprinting, one must be aware of this property. If the last ink printed is not sufficiently transparent, the overprinted color will shift toward the last printed ink. The opacity can be determined by checking the ink color on the ink bars of the squeegee.
(2) Color
The side-by-side scraping can be used to compare the colors of various colored inks, especially for magenta inks in color printing. The pigments of this ink include mineral red and Rhodamine yellow, and the mixture of the two. Unless the color of the ink used for the two printings is the same, it is not possible to have a uniform color.
(3) Ink intensity or pigment concentration
The problem often encountered in color printing is not whether the ink contained in the ink is the same, but whether the percentage of the pigment content is the same. The latter problem is that in order to obtain the same color saturation, inks with a low pigment content need a thicker ink film than those with a high content.
The detection of the pigment content, sometimes referred to as the "whitening" test, involves mixing 1 part of the ink with 50 parts of the opaque white ink, and juxtaposing the ink with the same proportion of the standard ink against the white, and visually checking the difference between the two ink strengths. Densitometer red, green and blue channel readings can be used to quantify this difference. The addition of the white opaque ink continues in the darker ink that is scraped side-by-side until the two inks are the same, thus giving a relative quantitative description of the pigment concentration relationship between the two inks.
(4) Ink adhesion
The ink adhesion affects the adhesion of the ink and the problem of peeling the paper. The adhesion of the two inks can be compared with a simple test. The two inks are each coated with a bit of ink and applied to the plane. Each of the two inks is pressed against each ink sample and the fingers are quickly lifted. The disadvantage of this test method is that a quantitative absolute adhesiveness cannot be obtained and only the relative value of the adhesiveness can be obtained. Of course, the adhesion value can now be quantitatively measured under certain conditions using an electronic ink sticker or other adhesives.
The quality of raw materials has a great influence on the final quality of prints.
The quality of raw materials can be guaranteed by looking for manufacturers or sellers who can provide high-quality raw materials, or rejecting unqualified products by testing incoming raw materials. With regard to the detection of raw materials, in spite of the inconvenience of testing, large-scale printers should realize that the investment in testing is still much less than the benefits. Small printing companies can also obtain significant benefits from inspections, as long as they purchase small-scale test equipment with low investment and use existing employees to perform test operations.
As a company's manager, when you intend to implement quality control of raw materials, you should first consider two aspects, weigh whether the amount of investment in testing equipment is less than the benefits that can be brought about. Furthermore, it is necessary to exhaustively analyze and analyze the quality problems and the causes of these problems, so as to better control the quality of the raw materials in the printing process.
A large number of detection methods, testing instruments, and inspection images can be evaluated by the printing factory for raw materials, which means that almost all paper or ink properties can be detected to comply with the established standards. The key question now is what testing methods should be used and how much testing should be done on various occasions.
When testing paper or other substrates, it is difficult to obtain a representative sample. It is very difficult for a stack of papers, especially large ones, to randomly sample from them without re-stacking them. For webs, the detection is not possible except for the (less representative) outer layer.
In general, the sampling of ink and photosensitive materials is not a problem. Another problem that should be considered when sampling raw materials is that some detection methods are destructive. Such as paper, cardboard strength testing, photosensitive material sensitivity testing, its samples will be damaged and consumed.
For the selection of a test method for a material, consideration should be given to the use of tests that can obtain data relating to defects in printed images or obstacles to print production.
The frequency of detection of a certain property must be based on the tolerance for the performance change, which in turn is related to the level of quality defects allowed by the final print. The more stringent the quality requirements of printed products, the more frequently the raw materials need to be inspected.
For most printing companies, it is impossible to spend as much time, money, material resources, and manpower on detecting raw materials as government departments or extra-large printing companies. The benefits of testing may not be enough to cover the cost of testing. However, this situation refers to a large-scale inspection, but in fact most printing companies can conduct small-scale inspections. All printing companies can properly invest in those tests that are cost-effective.
The following are the tests that control the factors affecting color reproduction:
1, paper detection
Some tests can be implemented with very simple devices.
(1) Thickness
To maintain proper printing pressure on the printer, use a caliper gauge. The thickness of the paper should also be measured with a micrometer. Usually ten sheets of paper are used to measure five points.
(2) Opacity
The opacity visual scale is an effective measurement tool. A set of characters is printed on a darkened background dot background, the paper under test is covered on it, and the character begins to look unclear somewhere on the scale, which indicates the opacity of the paper.
(3) Absorptivity
K&N ink is probably the most commonly used and cheapest test method. The ink is composed of a gray dye and an oil base, which is applied to a paper sample and is removed after two minutes. The remaining ash density is the absorbency of the paper.
(4) Gloss
The gloss meter was measured along the direction of the paper and the average was taken.
(5) Paper efficiency
This test combines the gloss and absorbency of the paper to determine the effect of the substrate on the ink film color. Absorptive but 100% gloss paper can print the most saturated colors. In contrast, 100% of absorptive but matte paper (such as newspapers) will print very poor colors.
(6) Color and lightness
The approximate properties of paper color and brightness can be obtained by measuring the density of red, green, and blue color filters after calibration using a reflection densitometer. Ideal paper, the density under each filter should be consistent, low density, indicating high lightness. The visual comparison method of paper samples is more meaningful for the detection of paper color and lightness.
(7) exposed leather
The Dennisson wax stick peel test, despite its shortcomings, is still a suitable method for determining the peel resistance of a particular substrate. The end of a certain grade of wax stick is melted and pressed against the substrate under test. After fifteen minutes, it is quickly pulled up and the exposed fiber or paint is inspected on the end face.
As with many other raw material tests, the relative significance of the wax stick test is greater than predictive. In other words, if the peeling does not occur, then when the paper whose peel strength is higher than 10 is printed under the same conditions, there will be no problem of peeling.
2, ink detection
The first step in evaluating the ink is to scrape the ink, preferably on the paper to be printed. It is usually operated with a wide knife, or a thicker ink layer can be rolled out with a small ink roller. When comparing two inks, it is generally required to scrape two ink samples on the same piece of paper in parallel. There is often an on-site ink bar in the middle of the squeegee.
(1) Opaqueness
Some inks, such as yellow ink, are not as transparent as other inks. In the case of color printing or overprinting, one must be aware of this property. If the last ink printed is not sufficiently transparent, the overprinted color will shift toward the last printed ink. The opacity can be determined by checking the ink color on the ink bars of the squeegee.
(2) Color
The side-by-side scraping can be used to compare the colors of various colored inks, especially for magenta inks in color printing. The pigments of this ink include mineral red and Rhodamine yellow, and the mixture of the two. Unless the color of the ink used for the two printings is the same, it is not possible to have a uniform color.
(3) Ink intensity or pigment concentration
The problem often encountered in color printing is not whether the ink contained in the ink is the same, but whether the percentage of the pigment content is the same. The latter problem is that in order to obtain the same color saturation, inks with a low pigment content need a thicker ink film than those with a high content.
The detection of the pigment content, sometimes referred to as the "whitening" test, involves mixing 1 part of the ink with 50 parts of the opaque white ink, and juxtaposing the ink with the same proportion of the standard ink against the white, and visually checking the difference between the two ink strengths. Densitometer red, green and blue channel readings can be used to quantify this difference. The addition of the white opaque ink continues in the darker ink that is scraped side-by-side until the two inks are the same, thus giving a relative quantitative description of the pigment concentration relationship between the two inks.
(4) Ink adhesion
The ink adhesion affects the adhesion of the ink and the problem of peeling the paper. The adhesion of the two inks can be compared with a simple test. The two inks are each coated with a bit of ink and applied to the plane. Each of the two inks is pressed against each ink sample and the fingers are quickly lifted. The disadvantage of this test method is that a quantitative absolute adhesiveness cannot be obtained and only the relative value of the adhesiveness can be obtained. Of course, the adhesion value can now be quantitatively measured under certain conditions using an electronic ink sticker or other adhesives.
The quality of raw materials has a great influence on the final quality of prints.
The quality of raw materials can be guaranteed by looking for manufacturers or sellers who can provide high-quality raw materials, or rejecting unqualified products by testing incoming raw materials. With regard to the detection of raw materials, in spite of the inconvenience of testing, large-scale printers should realize that the investment in testing is still much less than the benefits. Small printing companies can also obtain significant benefits from inspections, as long as they purchase small-scale test equipment with low investment and use existing employees to perform test operations.
As a company's manager, when you intend to implement quality control of raw materials, you should first consider two aspects, weigh whether the amount of investment in testing equipment is less than the benefits that can be brought about. Furthermore, it is necessary to exhaustively analyze and analyze the quality problems and the causes of these problems, so as to better control the quality of the raw materials in the printing process.
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