Tinplate boxes are made of metal, so printing on them is not the same as printing on paper. Paper can “drink” ink, but metal cannot. So tinplate box printing has some special requirements.
First, the metal surface must be very clean and smooth. If there is dust, oil, or rust, the ink may not stick well. Second, workers need to put a special coating on the metal first. It is like putting a primer on a wall before painting. Third, the ink must be special ink for metal. It needs to stick tightly and not come off easily.
Fourth, after printing, the box must be dried or baked in a special way. This helps the ink become strong. Fifth, the colors must line up very carefully. If not, the picture may look funny, like one eye is in the wrong place! Sixth, the printed box should be scratch-resistant and water-resistant, because boxes are often touched and moved.
Also, if the tin box is for food, the printing materials must be safe. They should not have a bad smell or be harmful. My teacher said this is very important.
