Mash temps and FG

[lyacovett]

OK, I am new to AG brewing, I did my first AG about a week ago. It was a sweet stout, with an estimated OG of 1.054 ... I ended up at 1.064. I wasn't concerned about it being way above what I expected, I wanted this to be sweet anyway.

I wanted a really full body stout, so I mashed high, I was aiming for 154 or so ... I ended up at 158 ... I figured what the hell, and just let it sit. I really only lost about a degree, so after an hour, I was still right around 158.

Now a week later, fermentation has quit at 1.030 ... much higher than I expected. I repitched with some nottingham, and still nada (its been 2 days) .. gravity still at 1.030.

This leads to my question, would the high mash temp make that much of a difference in the FG? I was expected around 1.020 ... but 1.030 ... could this really be the FG?

Like I said, I am new to AG, and really don't know how much the mash temp can affect the FG.

Thanks for the help guys.

 

[Catt22]

Yes, the high mash temp can result in a high FG. This is a rather common occurance. Most often it is a result of the mash temperature being higher than what is measured for one reason or another. Inaccurate thermometers are probably the #1 culprit. Mash temperatures are never uniform throughout the mash, so it depends on when, where and how you measure it in addition to using a reasonably accurate thermometer. It can be tricky and this issue has caused the same problem for me more than a few times.

 

[squeekysheep]

ya even 1 degree can make a big difference. when i mash i always keep a little hot water around incase i need to bump it up and i always get my temp higher then my target and let it fall to the target range. then i mash in

have you checked your thermometers in ice water and at boiling?

 

[Yooper]

The mash temps do play a large role in the fermentability of the wort.

Also, since you made a sweet stout, you may have used some unfermentable sugars like lactose. That will make a higher FG, too, since the sugars are in there but can't be fermented.

 

[lyacovett]

My thermometer is fine, 212 at boiling. I know that I mashed high, and I stirred quite a bit, so the temps should have been pretty uniform throughout.

I knew that mash temps play a large role in fg, but I didn't think it would make it FG at 1.030 instead of 1.020, like I said, its not a huge deal, it tastes OK ...for being so green at least. I just didn't want to bottle it just in case. There was a lb of crysal 60 and a lb and a half of chocolate ... so there are quite a bit of unfermentables from those, but no lactose.

I guess I will just have to accept that the fg will be 1.030, and bottle in another week ... lesson learned I guess. I probably won't be mashing that high again. I got 4.5 abv instead of the 5.9 I was expecting ... it'll still be good I'm sure though.

 

[Pat_13]

You could also pitch a higher attenuating yeast to drop it a little more.

 

[lyacovett]

Yeah, I originally pitched WLP005, that got it down to 1.030, I pitch Nottingham and got it to 1.030 ..... I'll give it a week to clean up and see if it drops any more, but I don't think it will.

 

[Catt22]

You could also pitch a higher attenuating yeast to drop it a little more.

Probably wouldn't help as there's likely nothing fementable left for the yeast to eat. When it's done, it's usually done and short of brewing another beer to blend with it, there's not much you can do about it. Sometimes rousing the yeast will get it to drop another point or two, but usually not.

 

[lyacovett]

So ...... you think its safe to bottle?

 

[Catt22]

So ...... you think its safe to bottle?

Yes, but I would wait another week or so for two reasons. It will allow more time for the beer to clear and it may possibly drop another point or two. Start planning your next brew while you are waiting. The week will go by quickly, you'll see.

 

[lyacovett]

Yeah, I just transferred to secondary last night to see if it would get the little guys going, but other than a little degassing, nothing. So I will give it the week to clear and let the yeast clean up, maybe even two weeks, then to the bottles. I already did another brew last night too ... so now its the waiting game.

Thanks for the help.

 

[JesseRC]

Yeah, I just transferred to secondary last night to see if it would get the little guys going, but other than a little degassing, nothing. So I will give it the week to clear and let the yeast clean up, maybe even two weeks, then to the bottles. I already did another brew last night too ... so now its the waiting game.

Thanks for the help.

I just reread your original post realized that you brewed this last week. You should have just left it in primary for another 2 weeks. I know all brewing instructions give you timelines, but seriously you just gotta go with the flow. I dont even check gravities on my beers until atleast 3 weeks. The only extra attention I give my brews is a slight warming up to 69-70 F when krausen is starting to fall and just the removal of the blow off tube.

I'd say forget about it for a while. It will get there.

 

[Schnitzengiggle]

I just reread your original post realized that you brewed this last week. You should have just left it in primary for another 2 weeks. I know all brewing instructions give you timelines, but seriously you just gotta go with the flow. I dont even check gravities on my beers until atleast 3 weeks. The only extra attention I give my brews is a slight warming up to 69-70 F when krausen is starting to fall and just the removal of the blow off tube.

I'd say forget about it for a while. It will get there.

+1 the worst thing about brewing is having to be patient, I usually don't fuss with mine until the 3 week mark as well, but there are exceptions of course.

For instance I just checked the SG on my 10 gallons of APA (brewed 10/24), I slpit it between two 5 gallon fermenters, and the fermentations between the two were completely different, #1 took off and was very vigorous and out lasted #2, #2 was slower to start, less vigorous, and finished earlier, but #2 also had a lower FG than #1, only 1 point, but I thought it was interesting. What I am getting at is, that if you notice something odd or have any questions or doubts, check the gravity, but just because it is finished fermenting doesn't mean it is finished.

I'd hate to wait 3 weeks to find out that I had a stuck or stalled fermentation just because I don't check on my beer once in a while, but I'd also don't want to rack to secondary or bottle too early for fear of a longer conditioning period.

 

[ultraplop]

Probably wouldn't help as there's likely nothing fementable left for the yeast to eat. When it's done, it's usually done and short of brewing another beer to blend with it, there's not much you can do about it. Sometimes rousing the yeast will get it to drop another point or two, but usually not.

Actually some higher attenuating yeasts will eat some more complex sugars than a lower attenuating one will. If you want to add more yeast to try and get your FG down, pitching a lager yeast is a good idea because lager yeasts eat more of the complex sugars than an Ale yeast will. Its also recommended to pitch them while they are active, so you will want to make a starter and pitch it after you see Krausen or after about 18 to 24 hours.

 

[Baron ken]

+1 the worst thing about brewing is having to be patient, I usually don't fuss with mine until the 3 week mark as well, but there are exceptions of course.

For instance I just checked the SG on my 10 gallons of APA (brewed 10/24)...
<snip>...
I'd hate to wait 3 weeks to find out that I had a stuck or stalled fermentation just because I don't check on my beer once in a while, but I'd also don't want to rack to secondary or bottle too early for fear of a longer conditioning period.

I brewed my IPA on 10/18 and it's been dry hopping since it went in the fermenter. I haven't done anything with it except monitor the temperature. I suppose I ought to check on it this weekend and probably get it kegged. It should be nice and clear.

 

[Hermit]

The mash temps do play a large role in the fermentability of the wort.

Also, since you made a sweet stout, you may have used some unfermentable sugars like lactose. That will make a higher FG, too, since the sugars are in there but can't be fermented.

A point I am not clear on. Raising the mash temp, lets say from 152 to 156 after 60 minutes. Do you end up with BOTH sugars at that point?

 

[JesseRC]

After 60 min it's probably fully converted.