Stalled fermentation with Safale S-04 (2024)

Hi folks,

I’m in the process of fermenting a batch of Espresso Stout from a Dark Rock part grain kit.
I’m using Safale S-04 dried yeast that comes with the kit.
I’m very Strict with my cleaning and sanitation process too.
And I ferment in a standard sealed bucket type fermenter with airlock.
Unfortunately I don’t have a brew fridge yet, so the ferment or sits under the stairs, which remain’s pretty constant with temp.

Temp range for this yeast is supposed to be 15C to 20C, but I read you should pitch at just above this, so I pitched at 23C.
Weather forecast was slightly off, so temp remained about 23C for the first week…I had thought the temp would drop.
Fermentation seems to go OK, but seemed to end after day 5.
I have had short fermentation before with other yeasts and easily hit FG, but this time the gravity stopped at 1.020, but target is 1.015
OG was 1.052, so a lot of fermentation did take place, but it has sat at 1.020 for 4 days now with negligible activity.

I’ve given it a taste when checking SG and it’s actually tasting good, no off flavours, etc.
So, the question is…in your opinions, would just leave alone for a few more days, and if SG is still stable, just bottle it with slightly lower ABV (difference is about 0.6 ABV) or should I try to warm the beer or stir it to try and wake up the yeast again?

obscure said:

It’s worth saying that S-04 is extremely quick to ferment out, I mostly use it in Bitter (typical OG 1.040-1.045) and I expect it to finish within about three days especially when it’s being used in the low 20s.

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Thanks, I’ve only used S-04 once before on an English ale, and that also missed its FG, even though the temp was kept in range the whole time.
Do you find you still hit FG target with these short fermentations?

KentishMan said:

Thanks, I’ve only used S-04 once before on an English ale, and that also missed its FG, even though the temp was kept in range the whole time.
Do you find you still hit FG target with these short fermentations?

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Pretty much, typically around about 75% attenuation (although as mentioned I primarily use it in Bitter typically 95% Pale Malt 5% Crystal) but on the whole find it to be a pretty solid and dependable yeast.

Not familiar with the kit, is a mash involved? If so, as Foxy says, may be a mash temp issue: I tend to mash low these days as it seems to help it ferment out lower.

Like others, S04 is one of my go-to yeasts and I've probably used in in over 100 brews, it is very reliable but I had had it struggle a bit with the odd dark beer. Even making the same dark beer twice produced significantly different FGs, which I could only put down to mash temp and/or fermentation temp. Never had this with lighter beers,

S04 flocculates and sediments well, so could have just settled out without fully attenuating given the fermentation temperature. Have you given it a rouse?

I don't think the pitch temperature was a problem, the lag phase can be done at a higher temperature.

https://byo.com/article/fermentation-time-line/

Sandimas said:

I think you pitched too high, sometime yeasts seem to run out of steam if they ferment too vigorously at the start

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Does anyone know a reason for this. Does yeast have a 'memory' like this. I've been thinking that if there is food available, the yeast will consume it, regardless of how much food was available beforehand.

Agentgonzo said:

Does anyone know a reason for this. Does yeast have a 'memory' like this. I've been thinking that if there is food available, the yeast will consume it, regardless of how much food was available beforehand.

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This appears to indicate that it's only the simple sugars that inhibit flocculation.

https://eurekabrewing.wordpress.com/2013/04/10/a-glimpse-into-yeast-flocculation/
I think the higher fermentation temperature with its quicker use of oxygen, nutrients and simple sugars, and subsequent rapid production of ethanol, all contributed to early flocculation, before it's metabolised the maltotiose etc.

KentishMan said:

Hi folks,

I’m in the process of fermenting a batch of Espresso Stout from a Dark Rock part grain kit.
I’m using Safale S-04 dried yeast that comes with the kit.
I’m very Strict with my cleaning and sanitation process too.
And I ferment in a standard sealed bucket type fermenter with airlock.
Unfortunately I don’t have a brew fridge yet, so the ferment or sits under the stairs, which remain’s pretty constant with temp.

Temp range for this yeast is supposed to be 15C to 20C, but I read you should pitch at just above this, so I pitched at 23C.

Click to expand...

No, pitching at the low end is better.

Fermentis recommend pitching into wort at 21-29C for their dry yeasts with the following.

In practice, the consecutive steps for direct pitching are:

• Fill the fermenter with 1/3 of the wort volume (up to the top of the CKT cone) at a temperature of 21-29 °C
• Sprinkle the active dry yeast cells directly in the fermenter
• Add the remaining 2/3 of the volume of wort at fermentation temperature to allow for mixing of yeast and wort.

https://fermentis.com/en/knowledge-...ecutive steps,cells directly in the fermenter