Theoretically speaking, the chemical composition of varnish should be determined. From an application point of view, it is a simple method to check the quality of the varnish purchased by the user.
â‘ Smell the smell. The solid content of UV oil is more than 95%, and the solid content is very volatile. Therefore, a good glazing oil smell is very small, it should be less smell than printing ink. The smaller the odor after curing, the better.
â‘¡Measure the solvent content. Put the varnish in a graduated vessel (diameter less than 50mm), place paper for 12h, and observe how much has evaporated. The drop in surface position is generally not seen. If the decrease is obviously observed, it means that there is too much solvent in the varnish, which is a fake product with the original varnish added with diluent.
â‘¢UV varnish is a non-conjunctival material. Like edible oil, it will not skin on the surface for a long time. Put a small amount of glazing oil on the surface of the glass sheet, and observe whether there is a skinning phenomenon after placing it in the dark place for 24h. No skinning means UV oil, otherwise it is fake UV oil.
â‘£Irritation to the skin. Put a small amount of varnish on the back of the hand and observe for about 20 minutes to see if the skin becomes red or blistered. Good varnished skin basically fails to respond, and general varnish will appear erythema, and bad varnish will make the skin blistered .
⑤ Observe the color of UV oil. Place UV ink in glassware with good transparency to observe, the lighter the color, the better the quality.
â‘¥ Viscosity. Different viscosities are selected according to different varnishing models, such as ordinary three-roller, gripper varnishing machine with a viscosity of 30 ~ 40s.
⑦ Leveling. Check the printed product after glazing and curing. If there are ripples, the leveling is not good. The solution is to first reduce the viscosity, heat or add diluent; second, extend the time of coating and curing to make it fully leveled, and then cure.
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