Why is counterstaining necessary when using a differential staning technique such as the gram stain?

Answer 1

The counter-stain allows you to see all the structures that were not stained with the primary stain. Without the counter-stain, all you would see is the purple-stained structures (nucleus, some cytoplasmic proteins), but you would have a difficult time observing the cell membrane and many cytoplasmic structures.

Answer 2

On the basis of cell wall, bacteria can be divided in to Gram's positive or negative bacteria. Those stained by primary stain are positive while those which are not stained by primary stain are subjected to counterstain that is safranin and are known as Gram's negative bacteria, safranin gives pink or red color to Gram's negative bacteria and helps differentiating them from Gram positive bacteria which are have a violet or purple color due to primary stain of crystal violet.

Answer 3

When staining with a differential stain, the tech doesn't stop to see if the first steps produced a result. All the steps are done (it is quicker) and then the results are read. The counterstain is a separate color from the primary satin. It is obvious, when complete, which is which.

Answer 4

to check for elephants