Question: what is the counterstain in the ziehl-neelsen acid-fast stain procedure?
Answer: Step 2: Smear Preparation (Review) ... 
Cover the smear with carbolfuchsin dye. ... 
Dry heat for 2 minutes.
Cool and rinse with water. ... 
Wash the top and bottom of slide with water and clean the slide bottom well.
Counterstain with Methylene Blue for 30 seconds to 1 minute.