First I took a microscope slide. It's worthwhile getting ones with frosted edges as these have a section that you can write on in pencil which makes labeling easier. I placed a small drop of water in the middle of the slide.
Heating the slide has the benefit of fixing the sample to the slide. This means the sample is firmly attached to the glass, denatured, and ready to receive the stain. For this reason it's usual to heat a slide for a short while even if it's air dried. You should be able to skip this with brewery yeast if you apply the stain delicately though.
Having dried the slide I took it to the sink and flooded it with methylene blue stain. The stain was left on for a few seconds and then rinsed off with tap water.
Did you not learn anything in the last 9 months!!!!!
OK this is what I do.
Make a 1:100 W/W dilution of the yeast slurry with cold tap water.
Mix well, then mix 1 ml diluted yeast with 1ml methylene blue.
Put onto slide and count 5 sets of 16 small squares.
To calculate the yeast concentration:-
Divide your white cell count by 80 (the number of small squares counted) to give the average number of cells per small square.
Multiply the answer by 4 million then by 200 (the dilution factor).
This will then give you the concentration of cells per gram in the yeast slurry.
Hope this helps."