All grain and high attenuation

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

phuff7129

Well-Known Member
Joined
Nov 5, 2011
Messages
557
Reaction score
44
Location
Lino Lakes
I just finished my 9th all grain 5 gallon batch, and again I had a lower than expected FG. Everyone of my all grain brews has attenuation far beyond expected FG. The brews have been good, but I am not sure if I am doing something wrong or right.

My first thought was my thermometer was off and I was mashing at much lower temps than I thought but I have used two different thermometers and got the same readings. I also calibrated both thermometers at freezing and boiling and they are on the money.

Here are the brews, yeast, mash temps, OG and FG's for my batches. If I list a liquid yeast I did a starter based on mrmalty.com specs. Take a look and let me know what you think.

Brew: Blonde ale
Yeast: Fermentis US05
Mash temp: 152
OG: 1.040
FG: 1.000

Brew: Belgian Pale Ale
Yeast: Wyeast 3522 Belgian Ardennes
Mash temp: 150
OG: 1.045
FG: 1.005

Brew: Belgian Wit
Yeast: Wyeast 3944 Belgian Wit
Mash temp: 152
OG: 1.046
FG: 1.006

Brew: Nut Brown Ale
Yeast: Nottingham
Mash temp: 150
OG: 1.056
FG: 1.010

Brew: Cream Ale
Yeast: Fermentis US05
Mash temp: 153
OG: 1.050
FG: 1.006

Brew: American Pale Ale
Yeast: Fermentis US05
Mash temp: 154
OG: 1.051
FG: 1.006

Brew: American Pale Ale
Yeast: Wyeast 1272 American Ale II
Mash temp: 151
OG: 1.050
FG: 1.006

Brew: Belgian IPA
Yeast: Wyeast 3944 Belgian Wit
Mash temp: 148
OG: 1.074
FG: 1.008

Brew: DFH 60 Minute IPA Yoopers Recipe
Yeast: Wyeast 1272 American Ale II
Mash temp: 153
OG: 1.065
FG: 1.008

Is this kind of attenuation normal for all grain? I am not sure if I have a problem that needs solving or not. The beer is great! I never got this kind of attenuation with extract.
 
They all seem to be finishing very low. Mash temps look good... How long do you mash? Is your sample at proper temp for your hydrometer calibration?
 
Mash time is 60 minutes for any temp 152 or lower and 45 for 153 or higher. I do calibrate for temperature for a 68 degree reading. I thought they were finishing kind of low. I just can't figure out why, or if it is a problem.
 
Most of those F.G. seem normal enough. But that blonde ale finishing at .000 does seem a bit off. That's really dry. Are you 100% sure that your hydrometer and thermometer are spot on?
 
Yes I have used 2 different calibrated thermometers and I have 2 hydrometers that read the same. It's got me scratching my head. The beers don't seem overly dry or watery. I don't know that my palate is that great but the beers have the taste and body I am looking for. I always ask myself what problem am I trying to solve and maybe there is no problem if the beer is good.

Could it be unstable fermenting temperature? I ferment in my basement and the temp will fluctuate 2-4 degrees, between 64 and 68 degress. I leave all of my beers in primary for 3-4weeks.
 
Like I stated in my earlier post. Those other F.G. seem pretty normal. But that blonde ale ending at .000 does seem weird. And if you want a more stable fermenting temp try a swamp cooler its not ideal but it might help. But if overall your beer taste good that's all that really matters!!!
 
If the beers have the taste and body you're looking for, then what's the problem? Although you could end up with a higher abv ....you could always add some unfermentables like dextrin if you think you want a higher gravity.
 
Just because you have two hydrometers that read the same, does not necessarily mean they are both accurate. Most of the hydrometers that I have owned were off by 2 - 3 points. You can easily check this by measuring a sample of water at the appropriate temperature. If it reads < 1.000, just add the error to each of your gravity readings.

-a.
 
I bought myself an hydrometer just for finishing gravities. It's much easier to calibrate and it's much more precise.

Another thing to look for would be wild yeast. If you drink all your beer young, there could be something funky going on without it being apparent in the taste.
 
I have also been getting very low FGs using US-05. I have made various pale ale recipes with OGs in the 1.065-1.080 range. The mash temps were in the low to mid 150s. All of them have had final gravities well under 1.010, typically 1.006. They taste decent, but they are dry and at least a percentage point higher in alcohol than the recipe indicated. I'm fairly certain that my thermometer and hydrometer are reading correctly. On one batch, I increased the mash temp to 160 to see what would happen, and I got a FG of 1.015. So increasing mash temp did seem to work. It just bothers me that my mash temp had to be increased by more than 5 degrees to get there. Also, I am making smaller batches (3.5 - 4 gallons into the fermentor) and pitching the entire yeast packet. I have wondered if that has anything to do with it.
 
I have also been getting very low FGs using US-05. I have made various pale ale recipes with OGs in the 1.065-1.080 range. The mash temps were in the low to mid 150s. All of them have had final gravities well under 1.010, typically 1.006. They taste decent, but they are dry and at least a percentage point higher in alcohol than the recipe indicated. I'm fairly certain that my thermometer and hydrometer are reading correctly. On one batch, I increased the mash temp to 160 to see what would happen, and I got a FG of 1.015. So increasing mash temp did seem to work. It just bothers me that my mash temp had to be increased by more than 5 degrees to get there. Also, I am making smaller batches (3.5 - 4 gallons into the fermentor) and pitching the entire yeast packet. I have wondered if that has anything to do with it.

I have read that overpitching can increase the attenuation, and also introduce off-flavors, but the effects of underpitching are usually much more severe. In your case, you may be overpitching slightly with fresh yeast and a 3.5g batch at 1.065, and you may be underpitching slightly with a 4g batch at 1.080.
At both limits, it is my opinion that the degree of over/under pitching is so small that it can be ignored.

-a.
 
How are you measuring the mash temperature? What kind of mash tun are you using? I.e., are you sure that the bulk of your grain is at the temperature that you are measuring for the duration of the mash?
 
How are you measuring the mash temperature? What kind of mash tun are you using? I.e., are you sure that the bulk of your grain is at the temperature that you are measuring for the duration of the mash?

For me, I am using the 5 gallon drinking cooler type. I use a 3" digital probe to monitor temperature. That means that I take my samples near the top of the tun. I have worried about temperature variation in the tun, so I have taken a few readings at the valve. These typically come in 1 - 2 degrees F lower than at the top. I also lose about 2 degrees over the hour mash (top and bottom). I did have one batch where I hit the OG/FG that I wanted (1.060/1.014), but this required a starting mash temp of almost 160F (measured at top). I'm fairly certain that my thermometer is calibrated to within a degree or so.
 
Stirring the mash thoroughly at the start and every 15 minutes or so after that will help even out any temp variance, as well as take care of dough balls and ensure complete conversion. Preheating the mash tun also helps with mashing at the right temp, as experience has taught me. As long as the end product is satisfactory, I wouldn't worry too much about the process. Extract generally is less fermentable, since it has carapils added in. If you want a higher fg, you can always add some unfermentables, mash higher, omit simple sugars or use less aggressive yeast strains. You might consider mashing for shorter periods of time, maybe 30 minutes or so. Almost all the starches have been converted within ten minutes; after that you're mostly changing dextrins to simple sugars.
 
That's weird. I use a cooler and my temps are LOWER at the top than the bottom, significantly at times. Also, by the end of the mash the sides are cooler than the center.

Are you re-using your yeast? It's possible they have a slight infection that doesn't manifest itself flavor-wise but is aiding attenuation. Of course your equipment could also have a mild infection or you could have wild yeast present in your environment.

I'd get another thermometer or borrow a few from friends, to verify. Mashing at 160 and ending up at 1.014 doesn't seem right unless you lost 5+ degrees over the course of the mash. How long are you mashing? Sorry if you covered that already. I do 3-8 hour mashes and so in my case I HAVE to start high because the temp will gradually drop and ferment more in the beta range, causing a more fermentable wort. Again, if you're losing a lot of temp (take mash temp after mash in several places, too. Invest in a long probe thermometer)...that would affect fermentability.
 
What's your mash thickness?

It seems to be a lot easier for me to get my mash temperatures uniform and stable with thinner (or, "un-thick") mashes--say, strictly greater than 1.25qt/lb. The amount of variation in a thick mash, after (seemingly) a lot of stirring, was shocking to me. It made me seriously consider upgrading to a recirculating mash system.

But mashing just a little thinner works fine. I just do a decoction on the step schedules, instead of trying to save space in my tun at mash-in. :D
 
One other thing I don't see mentioned here is your sparge process. Specifically:
1. Are you doing a mash out to raise the temp of your grain bed?
2. What type of sparge do you do, fly or batch?
3. Are you putting your kettle on the flame as soon as you have a couple of gallons collected?

The reason I ask is that any amount of time your grain or wort spend in conversion range is still potential conversion time. I batch sparge and was just sparging with straight 172-ish water and no mash out. My beers were finishing dry and thin until I started monitoring my grain bed temps. I realized by not performing a mash out step, my wort was staying at conversion temps for 15-20 min longer than I was accounting for.

I'm still not set up to get my wort right on the burner when sparging. But my beers do get 1-2 gallons of boiling water right before I collect the first runnings. My grain bed goes up past conversion temp to about 163-5, and shuts down conversion.

I did this on a Lawnmower beer recently. Mashed at 149 to get good ferment ability. But I mashed out, getting the bed to 163 before sparging. A 1.048 SG finished at a respectable 1.011. Dry enough to be refreshing but still with decent mouthfeel.
 
You may be on to something for me. I do not do a mash out and I double batch sparge at 168. So based on what you are saying I am still converting fermentable sugars the entire time I am sparging which makes sense. That could explain my consistently low fg's.
 
And there's two methods to correct this:

1. mash a few degrees higher (find the sweet spot) to accomodate for this.
2. mash-out.
 
Yes. Mashing out made a huge difference for me. I am also looking at re-engineering my set up so that I can get my first runnings on the boil right after collecting them.
 
Yes. Mashing out made a huge difference for me. I am also looking at re-engineering my set up so that I can get my first runnings on the boil right after collecting them.

Perhaps use a bottling bucket as an HLT so your kettle is free when you run the first wort off.
 
You may be on to something for me. I do not do a mash out and I double batch sparge at 168. So based on what you are saying I am still converting fermentable sugars the entire time I am sparging which makes sense. That could explain my consistently low fg's.

I'm thinking that my situation may be the same. I don't do a mash out, and I don't get the first runnings on the flame right away. I collect the first runnings (~2 gal) after an hour mash, then let them sit in the brew kettle for 20 or 30 minutes before the second runnings are added. I brought this up to my LHBS guy a couple of weeks ago. His response was that the conversion is pretty much done in the first 10-15 minutes, so that extra time at low temp shouldn't matter. But from what I have heard here, I'm not sure that is the case. It sounds like the conversion may be a little more complex. I think for my next batch, I will mash at the original target temp (~154), reduce the mash time to about 30 minutes, and get the first runnings on the flame immediately.

And thanks phuff7129 for letting me piggyback on your question!
 
Conversion is not "done" at all, not even within the hour. How do I know? Because I do 3+ hour mashes exclusively now. It's harder than you think to denature beta amylase, so it will keep working unless you mash really high or mash-out. When I've overnight mashed at 153 it created a wort that attenuated down to about 1.001 (from 1.049).
 
Conversion is not "done" at all, not even within the hour. How do I know? Because I do 3+ hour mashes exclusively now. It's harder than you think to denature beta amylase, so it will keep working unless you mash really high or mash-out. When I've overnight mashed at 153 it created a wort that attenuated down to about 1.001 (from 1.049).

Wow. Ok. I remember you mentioning the 3+ hour mashes in your previous post. I have never heard of that. What are you getting from that? Maximum fermentability? A particular flavor profile? Or both, I guess?

As far a mash-out, I have seen the various opinions on whether or not it is a necessary step. What I don't quite understand is how it would work with the batch sparge method. If I am doing my sparge at 170F (~185F strike), then my second runnings have essentially been through mash out. Right? And if I put the first runnings on the flame right away (like I plan to do), then they will go through mash out when they get to 170F. Am I thinking about this right?
 
Wow. Ok. I remember you mentioning the 3+ hour mashes in your previous post. I have never heard of that. What are you getting from that? Maximum fermentability? A particular flavor profile? Or both, I guess?

As far a mash-out, I have seen the various opinions on whether or not it is a necessary step. What I don't quite understand is how it would work with the batch sparge method. If I am doing my sparge at 170F (~185F strike), then my second runnings have essentially been through mash out. Right? And if I put the first runnings on the flame right away (like I plan to do), then they will go through mash out when they get to 170F. Am I thinking about this right?

First, I get flexibility with my time and an increase in efficiency by 10%. Now, I have to adjust mash temps to be much higher than recipes call for. I use 153, 156, 158 as "dry, medium, heavy", instead of 60m mashers using 150, 153, 155. The beauty is that I can walk away for however long I need and come back to my wort when it's convenient.

Yes, you're thinking of a mash-out properly. I still can't believe 15-20 minutes at mash temps is affecting fermentability that much...but I suppose it has at least some affect.

You can either add boiling water to the mash before first run-off (can be tricky to get the right amount. Subtract this volume from total sparge volume, too) or you can just run it off and get it on the flame (careful not to scorch).

The sparge addition coming in at 190 or so should get the grist up to 168, which is sort of the magic denature number.

I never did a mash-out when I did hour mashes and never had crazy attenuation...not sure why, but I didn't.
 
tre9er said:
Perhaps use a bottling bucket as an HLT so your kettle is free when you run the first wort off.

I have a separate kettle I use for an HLT so thy part is covered. My issue is volume and location. I have a stick with notches on it that is calibrated to my BK. I have been leaving my BK as the collection vessel so that I can keep track of the volume collected. (I mash/sparge in my kitchen and boil outside)

Had not thought about my bottling bucket though. It's marked so I could track my runnings. Then I could keep the BK outside on my burner and just take the runnings out to it as I collect them in the bucket.

Brewing next Monday. Will try that.
 
I have a separate kettle I use for an HLT so thy part is covered. My issue is volume and location. I have a stick with notches on it that is calibrated to my BK. I have been leaving my BK as the collection vessel so that I can keep track of the volume collected. (I mash/sparge in my kitchen and boil outside)

Had not thought about my bottling bucket though. It's marked so I could track my runnings. Then I could keep the BK outside on my burner and just take the runnings out to it as I collect them in the bucket.

Brewing next Monday. Will try that.

I used to collect in a bucket as well when I had a shared HLT/BK. In your case it would work to transport it outside and get it on the flame.
 
Here's an update on the discussion we had a few weeks regarding mash temperature and high attenuation:

I brewed a new batch of IPA 3 weeks ago. I borrowed a 2 foot long temperature probe from work so that I could test mash temperature at different depths in my water cooler tun. To my surprise I discovered that your claim of higher temperature at the bottom was correct! I followed my usual procedure, pouring ~3.5 gallons of strike water at ~168F into the tun. I added the grain and stirred like crazy for 5-10 minutes. Then I began testing the temperature with the long probe. The top was what I expected--about 154F. As I dropped the probe deeper into the tun, the temperature began rising. At the bottom it was 160F. At that point I decided to do some recirculation to see what effect that would have. I recirculated about half the volume. At the end of recirculation, the temperature stabilized and measured between 150F and 152F everywhere in the tun. I put the top back on and checked the temperature periodically for the next 30 minutes, and it stayed in the 150-152F range throughout. I brewed as usual and pitched a packet of US-05. I checked the gravity yesterday, and it was 1.008. This is lower than I wanted, but perhaps consistent with a mash in the 150-152F range. But now I am at a total loss of how to deal with my mash in the future. Maybe this is why a lot of people don't like the vertical mash tuns? Any comments would certainly be appreciated.

That's weird. I use a cooler and my temps are LOWER at the top than the bottom, significantly at times. Also, by the end of the mash the sides are cooler than the center.

Are you re-using your yeast? It's possible they have a slight infection that doesn't manifest itself flavor-wise but is aiding attenuation. Of course your equipment could also have a mild infection or you could have wild yeast present in your environment.

I'd get another thermometer or borrow a few from friends, to verify. Mashing at 160 and ending up at 1.014 doesn't seem right unless you lost 5+ degrees over the course of the mash. How long are you mashing? Sorry if you covered that already. I do 3-8 hour mashes and so in my case I HAVE to start high because the temp will gradually drop and ferment more in the beta range, causing a more fermentable wort. Again, if you're losing a lot of temp (take mash temp after mash in several places, too. Invest in a long probe thermometer)...that would affect fermentability.
 
You kinda have to use the law of averages on these. I take temps within a second of stirring and then I average the readings I get from the bottom and top, knowing it all averages out. They say putting foil over the top of your mash bed can help reflect the heat below and maintain temps better.
 
Back
Top