* KBA proposes to use Planeta universal splints or Ternes splints for glazed blankets and automatic splints without lining splints for bright gloss printing plates.
* The pressure between the anilox roll and the coating cylinder should be as low as possible.
Printing oil
According to Fogra, ghosting caused by the reaction of engine oil particles in the ink with the reverse side of the substrate can be prevented by the application of an aqueous coating. It is advisable not to use overprinted oil for this purpose, as this will only increase the ghost image.
* The boundaries of the surface tension of the granules are much higher than those of glossy coatings. This must be taken into account when choosing substrates.
Waterborne coating
* Use only solvent-resistant and alkali-resistant printing inks according to DIN 16524 (check with Schmid-Rhyner's SRAG test solution if required). Do not use delayed-drying or scratch-resistant inks, or anti-friction pastes. Fresh and overnight inks are also not suitable. The ink should be free of surfactants such as waxes or silicones; in waterless offset printing, silicone-free coating of the ink is a standard procedure.
* If the film is dried too quickly after being applied to a thick layer of ink, the ink film will break. This can be corrected by reducing the power of the drying unit or printing at higher speeds, increasing the amount of coating applied, adding retarders or using different coating methods.
* In the process of double-sided coating, the ink may collect on the coating plate. The amount of polish can be increased to correct this defect.
* Polishing oil may collect on the coating plate when processing certain images, so manual cleaning may be necessary. Matte gloss coatings are especially prone to this condition.
* Streaks in matt gloss coatings caused by minerals can be corrected by agitating the coating.
* If the surface tension of the substrate or ink is too low (should be at least 35 millinewtons), use an appropriate coating additive. In contrast, if the coating does not relax properly, add a surfactant.
* If the coating oil works below the minimum filming temperature, an orange peel-like surface will be formed. This can happen if the coating oil is stored at a low temperature or if it is not properly conditioned, or if the air that is blown onto the coating film is too cold.
* Bad abrasion resistance (nail test, laboratory friction slider) indicates that the setting of the drying device is too low to form a film. In general, the radiator power should be increased if the coating cannot be thoroughly dried.
* Brittleness of the varnishes indicates poor scratch resistance. The answer is to use a more flexible coating. If inks containing silicone or wax are the cause of this condition, different inks are used.
* If a coating has not been thoroughly stirred, stir it again. Any sheet with too thin varnishes should be refinished.
* The foam does not necessarily have to be caused by an anilox roller or a doctor blade cavity. So to check if the pumping system has sucked in air, you may need to add a suitable defoamer.
* If the substrate is too absorbent, apply a primer to seal the surface before applying the specified coating to achieve the desired gloss level. Of course, it is best to select the appropriate paper from the very beginning.
* Be prepared to reduce the viscosity caused by the temperature increase during high-speed operation of the printing press. If the initial coating viscosity is set at the lower limit of 25s (DIN 4 cup), there is no reserve. However, excessive viscosity can cause splashing when used with high-speed on-line coating. Use a rotational viscometer to keep the viscosity constant.
* The occurrence of sticking in the stack of paper indicates that the sheet has passed through the drying unit for an extended period of time (this may be due to the fact that the coating contains too much additive to prevent its breakdown) causing the stack temperature to become too high. If glossy coatings formulated for two-sided coating are used on one side of the light, sticking may also occur due to the glass plate effect (pressing between the printed sheets to tightly press them together).
* When the downtime is long, the coating unit should continue to run to prevent the coating from drying out.
* Coating metal inks (even with primers) may cause discoloration and chipping. It is necessary to cooperate with glazing manufacturers to conduct some tests.
UV Varnish
* In compound operation with aqueous coating, the second coating line eliminates the risk of water contamination and the water will not cure the UV coating.
* If sticking or odor problems occur repeatedly in the delivery pile, this indicates that the curing has not been adequate (test hardness). This may be due to high printing speed, dirty reflectors, or aging of the lamp.
* If even if there is sufficient continuous part, the coating oil cannot be spread, it may be that the UV coating becomes too thick because it is too cold. Warming the varnishes should work, which can be accomplished by heaters in the varnishes or infrared radiation in the continuous section. Another reason may be that the stack temperature is too low. If the amount of coating oil applied is too large, it can cause cloud-like spots and hinder spreading.
* When used with aqueous coatings, if the surface tension of the substrate is too low, use a suitable coating additive and use a method that avoids the use of surfactant-containing inks.
* If you want to perform offline UV glazing on paper that is printed with standard ink, you must remove the powder from the print sheet. If the ink is not completely dry, a primer must be applied before applying the UV coating.
* On the double coater, the primer and UV coating must come from the same supplier. Foaming varnish
* Foaming varnishes are usually water based and are compatible with the same inks as waterborne varnishes. They can be used with all of the above recommended inks with similar thermal sensitivities. Occasionally, heat-sealable, solvent-based foaming coatings are also used.
* Foaming coating oils can only be heat-sealed on hard elastic type membranes such as PET (G, A) or PVC. Recycled paperboard is the best type to use. (Scotch tape test on raw material: The paper coating varnish must tear off the cardboard fiber, because the varnish should always infiltrate into the fiber.) The supplier should determine the suitability of the paperboard for foaming coating.
* In order to ensure proper sealing of the varnish film and plastic film, the application amount should not exceed 6-8 g/m2. For some superabsorbent boxes with cardboard or cardboard and paperboard heat sealing, it may require two coats of coating oil. In some cases it is more economical to apply the primer for the first application because it is cheaper and the sealing of the cardboard surface is more effective than the foaming of the coating.
* Low-power infrared radiation must be used to ensure that the bubbling coating is not "heat-sealed" in the press.
* Blisters have a tendency to block the surface of the anilox roller and the coating oil transfer device, so the system must be thoroughly cleaned after the printing run. If production is interrupted for some time, the anilox roller should also be cleaned. The same requirements apply to special effects varnishes.
* The ideal storage temperature and relative humidity for boxboard before printing and for printed foaming cards and coating oils are 18-25°C (64-77°F) and 55%, respectively. Weilburger found that, if kept well, these foamed cards processed with the Senolith-WL foamed varnish can be used for up to two years. If storage conditions are not ideal, as long as they are adapted to environmental changes in advance, they can usually be processed without problems.
* Use a packaging machine to heat seal the foam card on the surface. The quality of the heat seal depends on the temperature, the build-up pressure and the plane parallelism of the heat seal tool and the length of the thermal contact (machine timing), which is based on the thickness of the board, the length of the heat seal tool, the type of diaphragm and the thickness of the coat. Definitely.
Polishes with special effects pigments and aromatic coatings
*Special effects pigments can be mixed in water-based and UV varnish. Aromatic varnish must be water-based. When selecting anilox rollers, the size of the particles must be taken into account. Rainbow pigments (up to 200 μm) and scented capsules (up to 30 μm) require a cell site 1.5 times the size of the anilox roller.
* At work, the coating oil with special effect pigments must be fully agitated and the aromatic coating oil must be cooled.
* Aromatic varnish is expensive (up to 500 euros for 1 kilogram), but it saves on use and is easily diluted. It is advisable to consult the varnish manufacturer for the best method of handling and applying the varnish. As an option, the "separator" can be mixed in the aromatic coating to prevent the tiny capsules from being crushed when applying the coating and in the paper stack.
* The pressure between the anilox roll and the coating cylinder should be as low as possible.
Printing oil
According to Fogra, ghosting caused by the reaction of engine oil particles in the ink with the reverse side of the substrate can be prevented by the application of an aqueous coating. It is advisable not to use overprinted oil for this purpose, as this will only increase the ghost image.
* The boundaries of the surface tension of the granules are much higher than those of glossy coatings. This must be taken into account when choosing substrates.
Waterborne coating
* Use only solvent-resistant and alkali-resistant printing inks according to DIN 16524 (check with Schmid-Rhyner's SRAG test solution if required). Do not use delayed-drying or scratch-resistant inks, or anti-friction pastes. Fresh and overnight inks are also not suitable. The ink should be free of surfactants such as waxes or silicones; in waterless offset printing, silicone-free coating of the ink is a standard procedure.
* If the film is dried too quickly after being applied to a thick layer of ink, the ink film will break. This can be corrected by reducing the power of the drying unit or printing at higher speeds, increasing the amount of coating applied, adding retarders or using different coating methods.
* In the process of double-sided coating, the ink may collect on the coating plate. The amount of polish can be increased to correct this defect.
* Polishing oil may collect on the coating plate when processing certain images, so manual cleaning may be necessary. Matte gloss coatings are especially prone to this condition.
* Streaks in matt gloss coatings caused by minerals can be corrected by agitating the coating.
* If the surface tension of the substrate or ink is too low (should be at least 35 millinewtons), use an appropriate coating additive. In contrast, if the coating does not relax properly, add a surfactant.
* If the coating oil works below the minimum filming temperature, an orange peel-like surface will be formed. This can happen if the coating oil is stored at a low temperature or if it is not properly conditioned, or if the air that is blown onto the coating film is too cold.
* Bad abrasion resistance (nail test, laboratory friction slider) indicates that the setting of the drying device is too low to form a film. In general, the radiator power should be increased if the coating cannot be thoroughly dried.
* Brittleness of the varnishes indicates poor scratch resistance. The answer is to use a more flexible coating. If inks containing silicone or wax are the cause of this condition, different inks are used.
* If a coating has not been thoroughly stirred, stir it again. Any sheet with too thin varnishes should be refinished.
* The foam does not necessarily have to be caused by an anilox roller or a doctor blade cavity. So to check if the pumping system has sucked in air, you may need to add a suitable defoamer.
* If the substrate is too absorbent, apply a primer to seal the surface before applying the specified coating to achieve the desired gloss level. Of course, it is best to select the appropriate paper from the very beginning.
* Be prepared to reduce the viscosity caused by the temperature increase during high-speed operation of the printing press. If the initial coating viscosity is set at the lower limit of 25s (DIN 4 cup), there is no reserve. However, excessive viscosity can cause splashing when used with high-speed on-line coating. Use a rotational viscometer to keep the viscosity constant.
* The occurrence of sticking in the stack of paper indicates that the sheet has passed through the drying unit for an extended period of time (this may be due to the fact that the coating contains too much additive to prevent its breakdown) causing the stack temperature to become too high. If glossy coatings formulated for two-sided coating are used on one side of the light, sticking may also occur due to the glass plate effect (pressing between the printed sheets to tightly press them together).
* When the downtime is long, the coating unit should continue to run to prevent the coating from drying out.
* Coating metal inks (even with primers) may cause discoloration and chipping. It is necessary to cooperate with glazing manufacturers to conduct some tests.
UV Varnish
* In compound operation with aqueous coating, the second coating line eliminates the risk of water contamination and the water will not cure the UV coating.
* If sticking or odor problems occur repeatedly in the delivery pile, this indicates that the curing has not been adequate (test hardness). This may be due to high printing speed, dirty reflectors, or aging of the lamp.
* If even if there is sufficient continuous part, the coating oil cannot be spread, it may be that the UV coating becomes too thick because it is too cold. Warming the varnishes should work, which can be accomplished by heaters in the varnishes or infrared radiation in the continuous section. Another reason may be that the stack temperature is too low. If the amount of coating oil applied is too large, it can cause cloud-like spots and hinder spreading.
* When used with aqueous coatings, if the surface tension of the substrate is too low, use a suitable coating additive and use a method that avoids the use of surfactant-containing inks.
* If you want to perform offline UV glazing on paper that is printed with standard ink, you must remove the powder from the print sheet. If the ink is not completely dry, a primer must be applied before applying the UV coating.
* On the double coater, the primer and UV coating must come from the same supplier. Foaming varnish
* Foaming varnishes are usually water based and are compatible with the same inks as waterborne varnishes. They can be used with all of the above recommended inks with similar thermal sensitivities. Occasionally, heat-sealable, solvent-based foaming coatings are also used.
* Foaming coating oils can only be heat-sealed on hard elastic type membranes such as PET (G, A) or PVC. Recycled paperboard is the best type to use. (Scotch tape test on raw material: The paper coating varnish must tear off the cardboard fiber, because the varnish should always infiltrate into the fiber.) The supplier should determine the suitability of the paperboard for foaming coating.
* In order to ensure proper sealing of the varnish film and plastic film, the application amount should not exceed 6-8 g/m2. For some superabsorbent boxes with cardboard or cardboard and paperboard heat sealing, it may require two coats of coating oil. In some cases it is more economical to apply the primer for the first application because it is cheaper and the sealing of the cardboard surface is more effective than the foaming of the coating.
* Low-power infrared radiation must be used to ensure that the bubbling coating is not "heat-sealed" in the press.
* Blisters have a tendency to block the surface of the anilox roller and the coating oil transfer device, so the system must be thoroughly cleaned after the printing run. If production is interrupted for some time, the anilox roller should also be cleaned. The same requirements apply to special effects varnishes.
* The ideal storage temperature and relative humidity for boxboard before printing and for printed foaming cards and coating oils are 18-25°C (64-77°F) and 55%, respectively. Weilburger found that, if kept well, these foamed cards processed with the Senolith-WL foamed varnish can be used for up to two years. If storage conditions are not ideal, as long as they are adapted to environmental changes in advance, they can usually be processed without problems.
* Use a packaging machine to heat seal the foam card on the surface. The quality of the heat seal depends on the temperature, the build-up pressure and the plane parallelism of the heat seal tool and the length of the thermal contact (machine timing), which is based on the thickness of the board, the length of the heat seal tool, the type of diaphragm and the thickness of the coat. Definitely.
Polishes with special effects pigments and aromatic coatings
*Special effects pigments can be mixed in water-based and UV varnish. Aromatic varnish must be water-based. When selecting anilox rollers, the size of the particles must be taken into account. Rainbow pigments (up to 200 μm) and scented capsules (up to 30 μm) require a cell site 1.5 times the size of the anilox roller.
* At work, the coating oil with special effect pigments must be fully agitated and the aromatic coating oil must be cooled.
* Aromatic varnish is expensive (up to 500 euros for 1 kilogram), but it saves on use and is easily diluted. It is advisable to consult the varnish manufacturer for the best method of handling and applying the varnish. As an option, the "separator" can be mixed in the aromatic coating to prevent the tiny capsules from being crushed when applying the coating and in the paper stack.
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