1 or 2 jars of washed yeast?

i'm brewing an IPA today and have some freshly washed 1056 to pitch into it. targeted OG will be 1.066 and I've got 2 jars of washed yeast. according to the graduations on the side, one has close to 75 ml of yeast in it and the other has about 50. mr. malty says i need 75 ml of thick slurry to pitch for that gravity, so, in theory, i should be able to just pitch the one jar, but should i just pitch both to make sure it's enough or do you think that'll be overpitching too much?

Just the one will be fine, assuming your measurements are of compact settled yeast. Best would be to use the 75ml, but you would probably be fine using only the 50ml if you had to.

yeah, i'll just try the 75ml one and see what happens.

If it's not too late, a certain amount of the yeast in the jars will have died, leaving less than 75ml of active yeast. I think Mr Malty has a calculator for what percentage of living yeast still remains...not sure how accurate it is though.

yeah, but i harvested this yeast very recently and it all looked really healthy, i went for the 75ml, it seemed like enough yeast. we shall see. it's a hop bomb so if i end up with a few esters from underpitching, it shouldn't be a big deal.

android said:

yeah, but i harvested this yeast very recently and it all looked really healthy, i went for the 75ml, it seemed like enough yeast. we shall see. it's a hop bomb so if i end up with a few esters from underpitching, it shouldn't be a big deal.

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Wait. How can you look with the naked eye and tell if its 75ml of healthy yeast or 50ml of healthy and 25 ml of weak/dead? Or any other combo.

I have a lot of yeast and want to know how to tell. What do I look for?

jalgayer said:

Wait. How can you look with the naked eye and tell if its 75ml of healthy yeast or 50ml of healthy and 25 ml of weak/dead? Or any other combo.

I have a lot of yeast and want to know how to tell. What do I look for?

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Get a graduated container, a lot of mason jars are graduated.

Well, according the Mr Malty pitching rate calculator, any harvested yeast slurry over 60 days old is at 10% viability. Which seems very low to me... After a quick search, I couldn't find any other information. I guess our best bet is to always make a starter...unless you're pitching from yeast you harvested within 2-4 weeks. I'd be more inclined to trust Mr Malty's calculations of the viability.

Read these threads, and make your own call. Seems like pitching old yeast will have plenty of viability...but then again it might not.

https://www.homebrewtalk.com/f13/viability-harvested-yeast-151084/
https://www.homebrewtalk.com/f13/testing-limits-yeast-viability-126707/

remilard said:

Get a graduated container, a lot of mason jars are graduated.

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Ummm. I know how to read a graduated container! Haha! Thats not what I was asking.

i can't tell for sure what the healthy/dead ratio is. however, i've seen dead yeast and know that it is a different color than the healthy, light beige color. in any case, the fermentation was plugging along this morning when i checked on it and all seems well.

just checked and we're at full krausen. it might have been a little slower than normal fermentations to build up to this point, but that may have been because the yeast wasn't in active mode when i pitched it. i was greeted with the most heavenly smell of hops when i opened my fermentation fridge to check on it just now... can't wait to drink this one.

storunner13 said:

Well, according the Mr Malty pitching rate calculator, any harvested yeast slurry over 60 days old is at 10% viability. Which seems very low to me... After a quick search, I couldn't find any other information. I guess our best bet is to always make a starter...unless you're pitching from yeast you harvested within 2-4 weeks. I'd be more inclined to trust Mr Malty's calculations of the viability.

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I like me some Jamil but what is happening here is that I believe he has taken a rate of loss of viability from Fix or a commercial source. Commercial breweries never repitch slurry that is more than a week past harvesting (and that would be good practice for the homebrewer too) so I think Jamil is putting a rate that is reasonably accurate for a week or too in his calculator and the calculator will extrapolate that well beyond the time period for which data was observed.

The reality is that it is best to pitch the slurry fresh and assume the viability is high. If you have 60 day old slurry and you want to know how viable it is you can either guess or buy a microscope and cytometer. There is no way to predict that.

if i had planned ahead, i would have just made a starter to make sure it was kosher.