Yeast Slurry re-use takes longer to stop fermenting

[The Baron]

Hi as anybody else had instances where re-using yeast slurry it has taken longer than usual to stop fermenting.
I find it has happened on 3rd generations plus, it works fine and chews through the wort but at days 9 plus still has a layer of fine bubbles on the surface which are almost certainly fermentation action as I have taken a gravity reading on one to determine if it drops any lower and it did.

 

[Slid]

I routinely re-use yeast from slurry by splitting the cake into 4 or even 6 x 250ml bottles which then sit in the fridge, sometimes for several months.
Rarely go down more than one "generation", but do get very high attenuation. Have not noticed it being longer, but as I always give it two weeks before thinking much about it, I would not be in a position to really comment, although longer would very much be consistent with higher attenuation.

Most yeasts I use are medium to low flocculators - US05, Belgian or Wheat yeasts.

 

[Cwrw666]

I usually find that when re-using yeast sludge fermentation gets off more slowly compared to sprinkling the original dried yeast on the surface and finishes at 1 gravity point higher than the dried. eg. 1011 instead of 1010. Might not be the case if you aerate your wort but I don't do that.

 

[The Baron]

I do not seem to have a problem with the yeast starting quickly it is that it seems to take longer to ferment out even though it is a vigorous ferment, it just seems to be going against what I would expect i.e it takes off quick enough, ferments fast enough so i would expect it to finish within 5 days and then clean up for a couple but it is still fermenting after 9 plus days, just can not get my head round it

 

[Cwrw666]

Maybe you're not putting enough slurry in?

 

[The Baron]

Maybe you're not putting enough slurry in?

Hi if anything I think I may be over pitching as I use 1/2 a litre of decanted slurry, do you think that is enough?

 

[foxy]

Check your gravity, take no heed of the airlock. If your gravity is remaining the same then it's finished. The beer is just gassing off.

 

[The Baron]

I did on one of them Foxy and it dropped a further 2 points that's what made me wonder what the hell was happening as the first and second pitch always ferments as you would expect and were clearing down by day 7ish.
I didn't know if it was a trait of 3rd generation plus pitching or just one of those anomalies you sometimes come across and can not put any logic to

 

[foxy]

Maybe the yeast is just knackered then, was the yeast from a high gravity brew?

 

[The Baron]

No the gravities I brew are generally not much higher than 1.040.
its just that it has happened on 2 separate occasions with different yeasts. I will just put it down to experience and by the way the brews did not suffer they just were a couple more days before kegging