Gold powder and silver powder are metal pigments, and are commonly known as gold-colored copper powder and silver-white aluminum powder. All of them use a mechanical method to scaly metal powder made by grinding, classifying, polishing and the like of copper and aluminum metal particles together with stearic acid.
1. Shape
Gold powder and silver powder must have the property of exhibiting a suspension phenomenon in a liquid medium in order to obtain the unique color-forming properties of the metal. The flaky powder has such characteristics, so the powder of gold powder and silver powder must be made into scale-like powder.
2. Color rendering
Chromaticity refers to the characteristics of gold powder and silver powder exhibiting metallic color under light irradiation. In general, a light reflecting surface with a large particle diameter of the powder is wide, and the color rendering property of a metallic color is strong, the particle diameter of the powder is small, the light reflecting surface is narrow, and the color rendering properties of a metallic color are weak.
Gold powder shows the color characteristics of the yellow system on the spectral reflectance curve, which is regarded as gold color in the actual production; the silver powder shows the color system characteristics of the white system on the spectral reflection curve, and is regarded as platinum in the actual production and production.
3. Gold powder
Gold powder, also known as copper powder, is an alloy powder consisting of copper and zinc. The difference in the amount of zinc causes the gold powder to have different colors. The zinc content of gold powder is generally 10% to 30%. Zinc content in 8% to 12%, reddish color, commonly known as red gold powder or red gold; zinc content in 20% to 30%, color cast green, commonly known as Qingguang gold or gold; in between The shade of light is called the crimson light powder. The zinc content of gold powder in different countries is different, for example, the British gold powder contains 72.2% of copper, 27.28% of zinc, 0.019% of aluminum, 0.12% of silicon, 88.3% of copper contained in gold powder imported from the United States, 11.29% of zinc, and 0.019 of aluminum. %, silicon 0.10%. The appropriate amount of silicon is added to the powder to increase the comminution of the copper-zinc alloy and to overcome the ductility, so that the powder forms a very small scale and increases the gloss.
The particles of powdered gold are in the shape of flakes, with an average particle size of about 50 to 100 μm, a thickness of about 0.1 to 1.8 μm, and a water surface covering ability (a certain amount of gold powder is sprinkled on the surface of the water, and the value obtained by covering the surface of the powder with gold powder is measured. The larger the measured value, the greater the hiding power of the powder and the better the use effect. It is generally 0.4 m2/g. Gold powder is based on the "mesh" as the unit of measurement of the commonly used gold powder mesh specifications, generally 220 ~ 400 mesh size specifications applied to the sheet metal; 800 ~ 1200 mesh size gold powder applied to the letterpress and intaglio; 1000 ~1200 mesh gold powder for
Offset offset printing gold.
The chemical properties of gold powder are generally not stable enough. In case of acid, alkali, carbon dioxide and sulfide gas, a chemical reaction will occur, which will cause the metallic luster to decrease or disappear.
In order to improve the surface oxidation resistance of gold powder, gold powder is often added with an appropriate amount of stearic acid during the production process to form a protective layer on the exposed powder.
4. Silver powder
Silver powder is aluminum powder, and although it has a silver-white metallic luster, the strength of the gloss varies depending on the size of the powder particles. If the particles are thick and flat, the metallic luster is strong. When the particles are small, the metallic luster disappears and becomes gray. Silver powder is based on the "mesh" as a unit of measurement, and is generally used as a silver ink for printing, using 400 to 800 mesh silver powder.
The silver powder is easy to be suspended, has strong covering ability on the water surface, has great hiding power, good stability, good reflection performance against light and heat, strong heat resistance, is not easy to change color, is not influenced by the weather, and has strong durability. However, the density of silver powder is small, and it is easy to fly in the air. When it encounters Mars, it will explode; in the case of acid, chemical changes will occur and the metallic luster will be affected.
(B) The link of gold and silver ink
The link material of gold and silver ink is a special type of varnish, referred to as gold or silver oil. They are made from specialty resins, dry vegetable oils and a variety of organic solvents that are refined at high temperatures. The brightness of the gold-silver ink printing layer mainly depends on the color forming property of the metal powder itself, the suspension property of the metal powder, the diameter and shape of the powder particles, and the factors affecting the affinity of the gold powder or the silver powder on the metal powder. Impact. Therefore, in order for the gold and silver inks to have good printability and achieve the desired printing effect, the gold transfer ink or the silver adjustment oil must have the following properties:
1. Must have sufficient viscosity, with the gold, silver powder blended basically reached the printing ink viscosity, fluidity and other performance indicators. If the transfer oil or silver oil has low viscosity and there is not enough tension, it will not
The gold and silver powders can be transferred well, which often causes problems such as stacking rollers and stack printing plates.
2. Low acid value, relatively stable chemical properties.
3. Can be evenly mixed with gold and silver powder to ensure the stability of metal powder suspension and good printing performance.
4. Can improve the color performance of gold and silver powder, make the metal powder more glossy and coloring power, so it must be kept transparent.
5. Must have fast-drying and fast-fixing properties. It should be printed on the printing material and dried quickly to prevent it from getting dirty.
Under normal circumstances, in the letterpress printing, the mixing ratio of gold varnish or silver varnish oil to gold and silver powder is 1:1 or 3:2; the mixing ratio in lithographic offset printing is about 2:3.
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