It is necessary to heat fix bacteria to the microscope slide. what happens when you pass the microscope slide through a flame a few times?

When you pass the microscope slide through a flame a few time, the bacteria smear becomes adhere to the slide.
Heat fixing of a bacteria involves passing the microscope slide on which a dried bacteria smear is spread through a busen flame three or four times in order to make the smear to adhere to the slide. The heat fixing preserve the morphology of the organism been fixed.