S-04 attenuation vs mash temp (2024)

I've just done a 1040 g all pale beer. Mashed at 68c. Got a final gravity of 1012 which I thought was a bit high. I've not used s04 for such a long time and im used to us05 fermenting right down. The attenuation works out at 71%.

well aerated, pitched and temp controlled.

Does s04 respond well to mash temp? I find us05 doesn't and always ferments low whatever.

That sounds about right. My first AG was a TTL clone (99% PA, 1% Chocolate) mashed at 68C and I got 71% attenuation with S-04. With a 66C mash I got 75% attenuation (Summer Lightning clone - 100% PA).

I think the fermenation temperature also makes a difference. Those two were both fermented at 18C but with a recent brew fermented at 20C I got 78% and that was with 10% crystal malt in the recipe.

Bumping this thread as I currently have a brew which is struggling to push below 1020 after an OG of 1042.

Mashed at 70c for extra body as its a low ABV brew. Brewers Friend reckons I should hit more like 1014. I use an accurate K-type thermocouple thermometer.

Temp held at 20c for the duration. A well aerated wort, and I pitched one sachet of hydrated yeast into a 5 gallon batch. Went off like a rocket for two days and then idled.

Added an extra 5g of rehydrated S-04 and roused existing yeast as it had already fallen bright. Also raised to 21c. It's fermenting, but very, very slowly.

Fingers-crossed I suppose. I'm used to using US-05 which sometimes goes beyond my attenuation expectations, but never less than.... I'm wondering if my yeast were overly active at the start of fermentation.

robsan77 said:

I find us05 doesn't and always ferments low whatever.

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Funny I always find it ferments out well I normally get 80% I would say

Covrich said:

Funny I always find it ferments out well I normally get 80% I would say

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I think there may be a difference in what is perceived as "fermenting well". I think all agree that US-05 seems to batter through to a low final gravity, even if a large quantity of the sugars are more complex.

Maybe I should have mashed 70c and used US-05, or mashed at say, 67c and used S-04.

It's all experience I suppose.

rodabod said:

.. I'm wondering if my yeast were overly active at the start of fermentation.

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S0-04 is a fast fermenter and can ferment out in as little as three days.

I made a porter using s-04 last week. Went like the clappers for three days and then went very quiet. I took the FG at 0.022 yesterday, an apparent attenuation of 70%. I was targeting 0.018, so have put it somewhere warmer and will rouse the yeast tonight to see if I can get it to drop a bit more. I mashed at 67oC for 1 hour, but the temp was bit over that for the first 5/10 minutes.

It's the first time I've used s-04 - it gave off a very strong banana aroma.

Those esters you get do fade away with time, but I did find that they were worse when fermenting at a higher temperature.

I'm not sure how much I like S-04, but I'm going to persist as I know that it can work well.

http://www.fermentis.com/wp-content/uploads/2012/02/SFA_S04.pdf
http://www.fermentis.com/wp-content/uploads/2012/02/SFA_US05.pdf

I'm not anything of an expert on the yeasts that are available nowadays but given the above plus the understanding that a 70c mash will produce a lot of unfermentable sugars, I think the results you got would be more or less expected.

Weird. I'd consider anything

than 1.012 to be abnormal. And I've been using S-04 for years now. [Most recently for very low alcohol brews (mashing at 68-9C I can still get 1.012 from an OG of 1.030). ---EDIT: Scrub this, I was using "Windsor" yeast for its well known habit of finishing high!---]

Talking of "abnormal", I tried that Safbrew "Abbaye" yeast the other day and got 1.008. That was from a bog standard 67C mash. And it took less than 48 hours to get there... from 1.061!

markcc said:

I made a porter using s-04 last week. Went like the clappers for three days and then went very quiet. I took the FG at 0.022 yesterday, an apparent attenuation of 70%. I was targeting 0.018, so have put it somewhere warmer and will rouse the yeast tonight to see if I can get it to drop a bit more. I mashed at 67oC for 1 hour, but the temp was bit over that for the first 5/10 minutes.

It's the first time I've used s-04 - it gave off a very strong banana aroma.

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Hi New to forum, just brewed my first porter and I think I may have made a mistake by using S-04, I was aiming for a high alcohol 8% beer, had a starting SG of 1.078 which was pretty much spot on to what I was aiming for, I was looking for final SG of 1.017. Had a mash temp of about 66degC. It fermented like the clappers for one day then has just about stopped, checked SG and it is 1.034, still decent at about 5.9% but not what I was after, I have tried giving it a good stir but dosnt seem to have re started it. Do I just leave it or can I throw in another packet of yeast, I have a spare packet of S-05. its a 15 litre batch. used to using S-05 which always ferments out fully. Any suggestions? pointers?

simonk68 said:

Hi New to forum, just brewed my first porter and I think I may have made a mistake by using S-04, I was aiming for a high alcohol 8% beer, had a starting SG of 1.078 which was pretty much spot on to what I was aiming for, I was looking for final SG of 1.017. Had a mash temp of about 66degC. It fermented like the clappers for one day then has just about stopped, checked SG and it is 1.034, still decent at about 5.9% but not what I was after, I have tried giving it a good stir but dosnt seem to have re started it. Do I just leave it or can I throw in another packet of yeast, I have a spare packet of S-05. its a 15 litre batch. used to using S-05 which always ferments out fully. Any suggestions? pointers?

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Sounds similar to what I was aiming for. OG was 0.077, but gravity is now 0.018 after two weeks (which is about 75% attenuation, so pretty much max for S-04). It went hard for three days and then really slowed, but did keep fermenting. I used one packet in 17litres having mashed at 67oC.

Not really sure what to recommend - I'm pretty new to brewing!

Have you tried raising the temperature a bit? Also, did you oxygenate well at the beginning?

Edit: just seen your other thread - looks like there's nothing to worry about!

markcc said:

Sounds similar to what I was aiming for. OG was 0.077, but gravity is now 0.018 after two weeks (which is about 75% attenuation, so pretty much max for S-04). It went hard for three days and then really slowed, but did keep fermenting. I used one packet in 17litres having mashed at 67oC.

Not really sure what to recommend - I'm pretty new to brewing!

Have you tried raising the temperature a bit? Also, did you oxygenate well at the beginning?

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being at constant 20degC, and stirred it well. my attenuation so far works out at about 72% so if what im reading is correct that is getting to the max for S-04, so don't wether to transfer to clean vessel and pitch another packet of yeast or should I leave it a while longer as it has only being 4 days,