I've been messing around with my new hemocytometer today attempting to estimate the cell density of the slurry in the bottom of my starter. I haven't been getting the results I expected so I figured someone with more experience might be able to point out where I'm going wrong.
This starter started as a Wyeast propagator into 3L of 1.04 SG wort. While aerating it with some airstones it bubbled over like crazy and I lost probably 2/3 of it down the drain. The next day I cooked up 2L of wort and added that, so it was back up to ~3L. I let that ferment for about three days, refrigerated, decanted off the wort, and added 3L more of wort. I let that ferment for about three days, washed it, and then refrigerated.
Today I poured off the wort and diluted 0.1ml of slurry into a liter of water. Going with Jamil's estimate of 3 billion cells per ml, I figured this should give me about 30 cells per 0.0001 ml hemocytometer square.
3*10^9 * 1*10^-4 * 1*10^-4 = 30
I tried to do a count with this solution but there were barely any yeast cells around. I dumped it out and diluted 1ml of slurry into a liter of water.
I counted three chambers (4 * 1mm^2 squares) of this solution and got these results:
11 + 21 + 21 + 19 / 4 = 18 =
1.8*10^8 / ml
8 + 16 + 21 + 11 / 4 = 14 =
1.4*10^8 / ml
32 + 19 + 13 + 15 / 4 = 19.75
My results for the three different chambers were relatively consistent, but all less than 1/10th of Jamil's estimates. I'm not going to have any stain until Tuesday, so these counts were all unstained. Any ideas why I ended up so far off from Mr. Malty?
I'm going to go do another dilution and some more counts, hopefully someone has some ideas by the time I get back.