How are plastic bags printed?

Gravure Printing

Gravure printing is a very old printing process that involves engraving the image to be printed on a cylinder or printing plate. The process was originally used to print magazines and newspapers in color over one hundred years ago. The images printed using gravure printing have deep rich, vibrant colors. Gravure plastic bag printing is used for high volume printing due to the expense of creating the printing cylinders.

The full name of gravure printing is rotogravure due to the fact that the etched plate is placed on a cylinder that rotates as it applies the text and image to the plastic material. Gravure cylinders are made of steel and plated with copper. A chemical etching process is used to place the text and images on the cylinder, a process that involves placing images and text on the cylinder using ultra violet light where a chemical etchant removes material from unprotected portions of the cylinder and leaves the images and text.

Cells that are etched into the cylinder control the amount of ink that is transferred to the surface of the plastic. As the cells get deeper, the intensity of the colors transferred increases. This aspect of gravure printing requires process control during etching and engraving to ensure proper cell depth.

As with flexographic printing, solvent inks are used, since they easily adhere to the surface of the plastic. Solvent inks are pigment inks that use oil or alcohol as a carrier for the ink. This factor is the reason that they are more permanent than water-based inks and why they work well with plastics