The ghost bar is the white line appearing in a printout caused by the print head touching the paper outside the perforation zone.
With a dot matrix printer, the print head moves back and forth across the page. At the end of each line, the print head shifts slightly to the left to print the following line without messing up the just-printed line. This slight movement is what creates the white line.
Head-tilt makes the print head collide with paper outside the perforations, which leaves a line on the printout. The tilt of the head moves the printhead about 1/10 into the left per line. It offsets the text on each line relative to the text on the line above it.
Using some other type of printer, such as an inkjet printer, can help avoid ghost bars. Inkjet printers have no head tilt mechanism, so they don’t have this problem.
A ghost bar is merely a bar that matches the page’s background color. This bar sits on the page where you would like to line up your element. Then, when printing, the bar will not be visible.
Ghost bars are crucial in printmaking to prevent inconsistency in print quality and inaccurate reproduction of colors. They also keep the printhead from harm.