So I'm trying to figure out how much slurry to use. I have a mason jar that has 400ml of Wlp001 that is about a month old. The yeast s topped with 400ml of beer. How do I calcuculate density for a re pitch or making a starter?
Calculating slurry
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stpug
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I estimate 1-2 billion cells per mL based on how well compacted the slurry is, and that is assuming that little was done to eliminate break material into the fermenter. Generally I use 1.5 unless it's extremely jiggly (1bil) or extremely compacted (2bil). The only way to do a lot better is with a good microscope.
I may be wrong here but i typically go by 1 ml = 1 billion cells, so 400 ml = 400 billion cells - 100 billion for every month...so i'd estimate you have about 300 billion cells.
http://www.yeastcalc.co/yeast-pitch-rate-and-starter-calculator is a great tool.
http://www.yeastcalc.co/yeast-pitch-rate-and-starter-calculator is a great tool.
I also like to use the 1.5B/ml estimate as an average. Based on advice in the Simple Yeast Storage sticky, I estimate 50% cell loss in 3 months (or about 17% per month). I use the Brewer's Friend starter calculator to determine how many cells I need from a given batch and use the estimates to determine approximately how much slurry I need.
I ignore all the calculating crap.
How do you estimate amount of yeast, how do you estimate amount of solids?????
Also calculators (actually I only know of Mr. Malty) under-estimate viability by a long way. I think MM says you have 10% viability at 2 months ....... but you still have 10% viability at 11 months - there is something wrong there. In my experience there is very little loss in viability after a month or two.
I generally just use about a quarter to third of the slurry for the next batch. From 'Yeast' it seems that the yeast at the end of fermentation is 6 times the recommended 'ideal' pitching rate. I figure some yeast have died after fermentation, so generally go with about a quarter of a cake. If stored for a few weeks, I go with a little more, like a third of the cake.
I have more confidence in my rough estimate than I do in any calculator, with lots of 'fuzzy' inputs and a dubious viability calculation.
How do you estimate amount of yeast, how do you estimate amount of solids?????
Also calculators (actually I only know of Mr. Malty) under-estimate viability by a long way. I think MM says you have 10% viability at 2 months ....... but you still have 10% viability at 11 months - there is something wrong there. In my experience there is very little loss in viability after a month or two.
I generally just use about a quarter to third of the slurry for the next batch. From 'Yeast' it seems that the yeast at the end of fermentation is 6 times the recommended 'ideal' pitching rate. I figure some yeast have died after fermentation, so generally go with about a quarter of a cake. If stored for a few weeks, I go with a little more, like a third of the cake.
I have more confidence in my rough estimate than I do in any calculator, with lots of 'fuzzy' inputs and a dubious viability calculation.
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