Cloudiness will result when the slides are placed in the alcohols (during Alcian blue 2.5) if the slides aren't

• A. Washed well with water after the nuclear fast Red stain
• B. Filtered before staining
• C. Stained longer
• D. Exposed to light

Answer: (A)

Cloudiness during the Alcian blue 2.5 step happens when any residual dye from the previous stain remains in the tissue. After staining with Nuclear Fast Red, the dye can interact with the alcohols used to dehydrate the slide, causing turbidity or clouding. Washing well with water after the Nuclear Fast Red step removes this excess dye (and the remaining moisture), so the subsequent alcohol dehydration proceeds cleanly and does not produce cloudiness. The other options don’t address removing residual stain before the alcohol steps, so they wouldn’t prevent the clouding.