(1) Purpose and definition.
Tinting Strength is used to determine the concentration between an ink sample and a standard sample. Therefore, under certain circumstances, tinting strength means the strength (concentration, saturation, density) of an ink. Because it is washed (removed) with a certain amount of ink and a certain amount of standard white ink It is measured after mixing, so it is also called the diluted (withdrawal) intensity (or diluted concentration) of the ink.
Tinting strength test is often called bleaching (Bleach) test in the United States, and mostly called Tint test in Europe.
In the past, the grades of ink products on the market were often distinguished by the amount of pigment content (that is, high-grade inks with high pigment content), which is actually an economic issue. In practical applications, Yi Yin said that because of the thinner printing of lithographic inks, the pigment content in the inks is required to be higher. When printing fine screen lines, the inks are also required to have a relatively high concentration. For solid prints, the strength of the ink can be lower. Of course, tinting strength can only indicate the amount of pigment content in an ink or its concentration, and it is not necessarily proportional to the concentration of the printed matter, because there are also ink transfer performance problems, dryness problems, and paper quality in the printing process. absorption properties, etc.
It can be seen that the strength of tinting strength is undoubtedly a concern of printing consumers: because it is related to printing costs.
The tinting strength of the ink is expressed in percentage, and its index is generally specified as 90~110%. In the determination, the standard sample is generally taken as 100%. If the sample is lower than 100, it means that the tinting strength of the sample is lower than the standard sample, otherwise, it is higher than the standard sample.
(2) Appliances and materials.
1. Utensils.
(1) Minor Ink Knife.
(2) scraping (ink) knife.
(3) Analytical balance (one-thousandth accuracy).
(4) Two pieces of glass of the same weight (approximately 8 x 8 cm)
2. Materials.
(1) Standard white ink
(2) Standard black ink (one can be fixed arbitrarily).
(3) Scratch sample paper.
(3) Method.
Weigh 2 grams of the standard white ink and 0.2 grams of the standard sample ink on an analytical balance with a glass sheet, and fully mix them evenly with a small ink knife. Weigh the standard Bai Cuan and the sample ink in the same way and fully mix them evenly.
Use a small ink knife to take a little diluted standard sample ink, place (apply) on the upper left of the scraping paper, then take a little diluted sample ink and place it on the upper right of the scraping paper, the two positions should be adjacent near but not connected.
Use the scraper to scrape the two inks on the paper from top to bottom into a thin layer. When the scrape is below the black line of about 5 cm, gradually put the scraper flat (even if the angle between the scraper and the paper becomes smaller), and the time between Reduce the force to make the ink form a relatively thick ink layer on the paper, and cover a small piece of cellophane on the thick ink layer to avoid contamination.
Then use experience to judge the difference between the diluted standard sample and the sample in terms of background color, face color and ink color.
If there is a difference in color between the two, it is necessary to adjust: if the color of the sample is darker (thicker) than the standard sample, the amount of white ink can be increased; if the color of the sample is lighter than the standard sample, the amount of white ink can be reduced Boundary quantity, until the color of the two reaches basically the same.
Tinting strength is calculated according to the following formula:
S=B/A×100%
In the formula: S = the percentage of tinting strength of the sample;
A = the amount of white ink used to dilute the standard sample,
B = the amount of white ink diluted in the sample.
(4) Matters needing attention.
1. When measuring the tinting strength of white ink, the standard sample and the weapon sample can be used to replace the standard white ink, and then add standard black ink that is one-tenth of the weight of the white ink. And when the colors of the two diluted ashtrays are inconsistent, the amount of white ink in the sample can be adjusted. The calculation formula remains unchanged, but in the formula, A is the amount of white ink in the sample, and B is the amount of white ink in the standard sample.
When measuring the yellow ink with a lighter color, for the convenience of observation and judgment, it is also possible to add blue ink to make it green.
2. The determination of tinting strength is meaningful only when the hue of the standard sample is similar to that of the sample, otherwise it is worthless. For example, it is meaningless to compare the tinting strength of a deep yellow with a lemon yellow. A common example is that the tinting power of red-phase yellow is greater than that of green-phase yellow, and the tinting power of blue-phase green is higher than that of yellow-phase green. This is all caused by the color difference. It is also easy to cause errors when the grayscale difference between the two colors is relatively large.
3. When mixing the standard white ink and the ink to be tested evenly, do not use excessive force to avoid grinding. This is because the tinting strength of the ink is related to the dispersion of the pigment in the diluted ink. Inconsistent grinding action can make a difference in results.
4. After the white ink is adjusted, it needs to be weighed again, so as to ensure the looseness of the measurement.
5. Mark with white ink. The white ink composed of 75% zinc oxide and 25% linseed oil type binder is commonly used in the world. Some use white ink containing 60% rutile titanium dioxide.
Standard white beams should not be too thin to avoid discoloration.
6. Since white ink is prone to flooding after mixing with other colors, it will change with the storage time of the scraped sample, which will bring difficulties to observation and judgment. Therefore, observation and judgment should be carried out in time after the scraped sample is scraped.
7. The coloring strength measurement we introduce here is a 10:1 method, and the standard (draft) issued by our country is 20:1. Most of the international law is 10:1. In some special cases, there are other practices with different ratios.
8. The determination of tinting strength generally has two methods: gravimetric method and volume method. True, the gravimetric method has a comparative quotient in accuracy. Most countries in the world adopt the weight method, and the volume method is only used in a few countries such as the United Kingdom.
9. Solvent-based ink can be measured by volume method. Of course, the accuracy of the gravimetric method is relatively high. When measuring solvent-based ink, the standard white ink generally contains 30% titanium dioxide, but its binder should be the same system as the binder of the measured solvent-based ink. Otherwise, it will not be able to fully mix evenly.
