[quote=“gusrotteyman”]Thank you Denny - that is helpful.
I am looking at the ‘Repitching from Slurry’ tab, and how do I know what to select for ‘Yeast Concentration billion/ml’? It has a slider that goes from 1 (Thin Slurry) to 4.5 (Thick Yeast). If the yeast layer is compacted on the bottom, and your liquid is clear and bright above, you can call it thick yeast.
It also has ‘Non-Yeast Percentage’ with a slider from 0 to 25. I assume that this is asking how much of the slurry at the bottom of the jar is the off white color - therefore not yeast. Correct? That is correct. The white layer is pretty much all yeast. The remainder, break material and hop debris, does contain some yeast also. Mrmalty may take this into account.
I don’t consider any of my harvested yeast being 4.5 billion cells per milliliter. I will go more middle of the road if the yeast component looks very clean. As every day goes by the yeast will compact more and more. I have seen compaction up to 100ml over a period of months after the beer on top of the yeast became clear, that is no suspended yeast remaining. Each yeast will be different as to how it compacts and even the size of the yeast cells will make a difference also as to how many per ml.
Viability of the yeast also comes into play. Yeast begins losing viability each day after the production date. In the case of rinsed yeast, the day active fermentation ended, or there abouts.
I always error on the side of over pitching rather than under pitching. Under pitching will affect the fermentation and resulting flavor of your beer. Over pitching, which is hard to do, has very little chance of being detrimental to the resulting beer.