How much washed yeast to use?

[Mark Weusten]

I am just started using yeast starters and washing yeast. I followed the instructions I found on the net to wash yeast and have a pickle jar around 600 ml in the fridge. I have washed this with boiled and cooled water once and looks clean but is not settling much after 3 days in fridge. Do you think this is all yeast or will it take longer to settle? My other question is how much to use, all very well using Mr Malty calculator which tells you how many mls to use when repitching from slurry. Surely all slurry yeasts are not created equal. For my next beer it tells me I need 107 mls of yeast. Wouldn't I be better to overpitch and add the majority of the washed yeast?

[Des Ross]

Hi Mark. After 3 days I would have thought the yeast would have mostly settled out of solution. I don't wash yeast but am lucky enough to have a dump valve on my conical to harvest yeast. I have often used over one litre of dense saved yeast in 25-50L batches and always ended up with great beer so if I was you I would definitely use the whole lot....you are only speeding up what nature does anyway! Like others I know, I have also dumped freshly brewed wort directly onto a full yeast cake from a batch I have previously kegged on the same day, again with great results. If I wasn't absolutely sure on the health of your yeast, I would also get a starter going 2-3 days before brew day, just to cover all your bases.

[Mark Weusten]

Thanks for that. I think it must be all yeast as it was a very clean ferment with no dry hop. Now dumping wort on a yeast cake from fresh beer, that sounds nice and efficient. I have a steam beer ready this weekend and may try this method. Mind you this was San Fran Lager yeast which I though wasnt particularly active so a starter may be wise with this....

[Damon Colbert]

I find it takes some experience to learn what proportion of your slurry is yeast vs. trub.  You can usually tell by colour once you've washed it once or twice. I just make an estimate based on proportion of the particulate, whitish trub vs the creamy, darker yeast.

Trub will settle out starting almost immediately, and might take half an hour.  Whatever remains will be mostly yeast, but the older generations will flocc out sooner (i.e. hours to overnight) than younger ones (days).

In terms of knowing how much of the slurry is viable yeast, there are ways if you are scientifically inclined (though I don't know of any homebrewers who go this far).  Methyl blue staining will give you some indication of what proportion of your slurry is viable, but you'd need a microscope.  

Methods are below if you're interested in knowing more.

http://www.whitelabs.com/content/cell-countingviability-testing-0

http://eurekabrewing.wordpress.com/2012/11/18/yeast-basics-check-ye...

[Mark Weusten]

Thanks Damon, I have an M44 and San Fran Lager second gen in the fridge. I think my biggest mistake was I didnt wash it in the fermenter and let settle for 30 mins before pouring the top off the trub. I would stir it up and straight into a container and chuck in the fridge for a few days before pouring off and adding water. Is that a fair comment of the correct procedure?

[JumpR]

Hi Mark I generally follow the procedure outlined here, which seems to have worked for me. 

Although I was a bit upset the other day upon discovering my washed yeast had frozen in the back of the fridge, thus cracking the glass jar and dropping yeasty goodness throughout the fridge!

[Mark Weusten]

Cheers for that article