Papanicolaou stain

[8][4][9] The pap stain is not fully standardized and comes in several formulations, differing in the exact dyes used, their ratios, and the timing of the process.

[3][2] Phosphotungstic acid is added to adjust the pH of counterstains and helps to optimize the color intensity.

[2] The EA counterstain contains Bismarck brown and phosphotungstic acid, which when in combination, cause both to precipitate out of solution, reducing the useful life of the mixture.

[2] Cell nuclei should be crisp, blue to black in color[12][13] and the chromatin patterns of the nucleus should be well defined.

[12] Ultrafast Papanicolaou stain is an alternative for the fine needle aspiration samples, developed to achieve comparable visual clarity in a significantly shorter time.