Varnishing is the last process of tinplate printing. The function of varnish is to protect the printed pattern, prevent mechanical damage, and at the same time give the printed tinplate product surface gloss and increase its aesthetics.
According to the different uses, printing tinplate varnish can be divided into two types: food tin containers varnish and non-food can varnish. The characteristics of food tin containers varnish are low yellowing at high temperature, high gloss, high hardness, resistance to boiling water sterilization and steam sterilization, and are often configured with non-drying oil alkyd resin, oil-free alkyd resin and acrylic resin. Non-food can varnish is mainly used for miscellaneous cans such as tea cans, metal candy tins, etc. This type of varnish is not resistant to boiling water and steam sterilization, but has good stamping resistance, high gloss and low baking temperature. Soybean oil alkyd resin is often used, peanut oil alkyd resin and epoxy resin.