Metallic inks are formulated from thin metal foils (aluminum foils are used for silver inks and copper foils are used for gold inks). When the inks are dried, these foils form a layer of stamped metal foil on the printed surface. When the metal pigment forms a thin layer on the surface of the print, it will produce a higher gloss of gold or silver ink. If you change the ink's metal flakes component or add color ink oil additives, the golden ink's color range will change from reddish gold to gold. Metallic gold or silver inks have a long shelf life and do not lose their luster even if they are stored in a container for a year. However, the metallic inks in the PANTONE Metal Color Manual are not very stable and should be used as soon as they are bought or prepared.
The use of softer particles for the formulation of metallic inks allows the metallic flakes in the ink to form a thin metal foil or to spread as far as possible on the surface of a single sheet of printing material for maximum gloss. Metal inks have low viscosity characteristics and are suitable for transfer between ink rollers, making the printing process cleaner. The coated paper absorbs the fixed ink better, so the ink on which the ink is printed is the brightest. Smooth non-coated paper also gives better results, but the gloss is slightly reduced. The rough surface of the paper prevents fine metal ink particles from forming metal foil on the surface of the paper, thereby reducing the printing effect of the metallic ink. Some substrates, especially polishing coating and clay-coated porcelain products, tend to hold the ink firmly on the surface of the substrate due to insufficient adhesion, often absorbing only the varnish in the ink. The particles stay on the surface. This phenomenon, known as "powdering," causes the color of the metal to peel off the surface of the substrate. To prevent "powdering", the amount of water should be set to a minimum, because inks with higher water saturation are more prone to "powdering." When printing on high coated paper or porcelain surfaces, an appropriate amount of desiccant should be added to the ink. Before printing with gold or silver ink, the surface of the substrate is usually sealed with a conventional oil-based clear white ink coated with a glue.
If "powdering" has already occurred, printing another layer of ink on the surface of the first layer will often make up for this fault. Overprinting the varnish can also overcome powdering, but this tends to reduce the metallic luster. Tip: For best results, it is recommended to use a metal plate instead of an electrostatic plate. This prevents the fountain solution from containing excessive amounts of glycerol or ethylene glycol because these non-volatile liquid media slow down drying. The opacity of the metallic ink can cause the operator to compensate for excess ink, causing the ink to appear unbalanced. Should avoid this situation as much as possible, because it will give the dampening system too much burden, resulting in paste plate (ink particles emulsified in the fountain solution) and dirty (ink adhesion to the plate non-graphic section). Even experienced printers use the excess ink to achieve the perfect metal effect. The best way to prevent these malfunctions is to add ink to a lighter color image so that it covers the image exactly. Then, increase the amount of ink, and adjust the amount of water supply so that it is slightly higher than the minimum value, so as to avoid the non-graphic part of the ink. The thin layer of metal will protrude during the drying process, providing a brighter luster.
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