What could've caused this and what to do about it?

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Ambrozyne

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On the 12th of Jan I brewed a very simple 2.5 gal all grain BIAB batch of English ale with 4.5 lb of Maris otter, 7 oz. of crystal 150 and 3.5 oz. of dextrose/ maltodextrine brewenhancer. Hopped with magnum and EKG hops. And chose S-04 for my yeast This was my 6th all grain BIAB batch. I Brewed with extract before.
I thought my mash went very well. mashed in @ 154F kept it quite consistent in my ghetto mash kettle but temp still dropped a little over the hour to 150-151F. Then I raised the temp toward the end to 156F. Added some yeast nutrient 10 min. Before flameout.
Pitched yeast ( dry, sprinkled on wort as per instructions)in the evening and put my fermentor on a heatpad cause the house gets very cold at night. Next morning saw action in the fermentor and in the evening high krausen. 24 hrs. later it fell silent. I had forgotten to turn the heatpad on at night... 2 days later I decided to check the gravity. It was still @ 1.020. Tried rousing the yeast a few times but nothing. Another 2 days later rechecked SG: still at 1.020. Decided to re- pitch another pack of s-04, this time rehydrated. Still nothing...
So, my 2 questions as in the title of this thread: why? My mash temps weren't that high were they? I checked my thermometer. It's o.k. And with my previous 5 batches I had no problem. And the maltodextrine I added wasn't enough to keep the SG this high, was it? So was it the drop in temperature because I forgot the heatpad the 2nd night?And then, what to do about it? What would you do? Sample tasted O.K. Of course a bit on the sweet side. In this 2.5 gal batch I used .42 oz of magnum(14.7%) @ 60 min and .35 oz of EKG(6.4%) @ 15 min. And .35 oz @ 5 min. Should amount to about 40 IBU's? I guess it's sufficiently bitter to offset the sweetness but would like it a little drier. Any suggestions?
 
When you say s-04 has an attenuation of 75%, does this mean with an OG of 1,058 I could reasonable expect an FG of 1.014-1.015? Just trying to get a basic understanding.
 
The mash sounds fine.
What temp did you ferment at? For how long? You said it got cold one night, but what about the rest of the fermentation? What FG did you expect?
 
Masskrug, with the heatpad temp is about 66-68F. I know its on the high side but its either that or highly fluctuating temps between 20 and 13 ( day and night) and i don't mind some esters in this english ale. So temps stayed around 66-68 the whole time except one night when they dropped to I guess about 57F. Fermentation lasted for about 48 hrs. I guess I expected an FG of around 1.016. Based solely on my exerience with previous batches.
 
The range for S-04 is 72-75% so based on the 1.058 you said you had, it should be anywhere from 1.014 to 1.016, so you are not far off. Did you do a starter? With a OG of 1.058 you really should have, or at the very least pitched 2 packs of yeast.
 
I'm just gonna throw a guess that your fairly high mash, good amount of crystal led to a lower fermentable wort and the yeast went after the dextrin first and slowed down due to a cold night.

Sounds like you made beer, just a little sweet.
 
The range for S-04 is 72-75% so based on the 1.058 you said you had, it should be anywhere from 1.014 to 1.016, so you are not far off. Did you do a starter? With a OG of 1.058 you really should have, or at the very least pitched 2 packs of yeast.

2.5 gallon batch, so he pitched plenty of yeast.

Are you sure your thermometer and hydrometer are accurate? You're not measuring FG with a refractometer are you?
 
I disagree with pitching 2 packs of yeast on a 2.5 gallon batch with a gravity of 1.058 because all you need is 101 billion cells according to mrmalty.com and 1 5g packet is enough to get the job done, but to get back to the reason why I think the yeast crapped out is because less fermentable sugars are produced at higher temperatures in a shorter time. beta enzymes are denatured at temperatures above 150, the high initial rest temperature may have produced a less fermentable wort. Beta amylase 140-150 Alpha amylase 150-170 the style should have a dry finish anyway so, next time try resting at below 150 then raise the tempature to above 150 (around 165) and begin your sparge
 
Thank you all for thinking with me. I guessed that one pack of yeast should've been enough. But because i sprinkled it in the wort dry I had second thoughts. The second pack rehydrated didn't help so I guess it wasn't a yeast count problem. I don't use a refractometer and i tested my hydrometer right before this brew. It is OK. The thermometer might be slightly off though. I'll check that again and account for it the next time I brew.
I will also take to heart the suggestion to mash in at a lower temp next time and see if that helps.
So in short, it was probably the amount of maltodextrine and crystal and a slightly high mash temp( check my thermometer!) that caused the partly unfermentable wort. I will ofcourse bottle this batch in a week or two and enjoy drinking it! Thank you all for your suggestions!
 
As others have mentioned... the lower range for that yeast would have put you at 1.016. Four points is not too far off, but there are many different variables to consider. This is mostly speculation.

1. Potentially unfermentable wort with all the dextrine, possibly higher mash for a bit; both could lead to troubles with fermentation.
2. Without rehydrating, you might lose 50% of your yeast, and I'm guessing that the ones left over are not exactly... healthy.
3. Swings in fermentation temperature would further stress the yeast, causing death... OR WORSE! :cross:
4. Fermentation is basically done at the end there, stopping at 1.020. Pitching more yeast might have little to no effect at that point.

All in all, no big deal. There are too many variables to get hung up over 4-5 gravity points. RDWHAHB :mug:
 
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