ABV too low / FG to high

[Evan Kingsbury]

Hi everyone-

I am new to home brewing. So far I have brewed (5) one-gallon batches. Each time, my OG is in the ball park, but my FG ends up way too high; resulting in a low ABV beer.

On my recent brew, I made a Sierra Nevada pale ale clone. Out of the mash, my OG was right on target at 1.054. After a 90 minute boil, my OG had dropped to 1.045 (not sure how that happened).


I used Safale US-05 dry yeast. After 11 days in the carboy, I checked FG, it was 1.025. I gave the carboy another 10 days, then checked again. FG is still at 1.025.

I am beyond frustrated. I have the same low ABV results no matter what I brew. Any ideas where I am going wrong? Thanks in advance!

 

[Iseneye]

You either measured the pre-boil and post-boil readings incorrectly, or you added water. The post-boil gravity can't be less than the pre-boil gravity.

With regards to the high final gravity there could be several things. Mash temperature and oxygenation are the two I am thinking of. The other would be your recipe - if it has a lot of unfermentables then you could end up with high FG.

The fact that your pre-boil and post-boil drop doesn't make sense makes me wonder if your FG reading is correct.

 

[NGD]

It might be helpful if you include a little more info on your mash temps, fermentation temps and aeration techniques.
Regardless of numbers...hows the beer?

 

[Evan Kingsbury]

Iseneye-

I have a feeling that the difference in my pre and post boil OG readings is due to temperature. For the pre boil reading the wort was likely 150 degrees F. I probably forgot to let it cool before using the refractometer. The post boil reading would have been 70 degrees F.

With regards to the high final gravity, what should I be looking for in the mash temperature and oxygenation?

I know my mash temperature fluctuates a bit. But is that a problem if my OG reading comes out at or close the receipe's target?

Could the high FG be a problem with the fermentation? I usually use US Safeale US-05. I've bought it from different stores over the span of a few months; so I'm doubting it'd be bad yeast. I'm thinking fermentation temperature may be to blame. We live in Michigan and the temperature varys in our house between 62 - 82 F.

Thanks again!

 

[Evan Kingsbury]

It might be helpful if you include a little more info on your mash temps, fermentation temps and aeration techniques.
Regardless of numbers...hows the beer?

Thanks for your response!

I heated my mash water to 160F. Then added my grains. Cover the pot, then wrapped it up tight in a blanket. I opened after 60 mins and took a OG reading which was too low. So I put the mash pot back on the stove, heated it back up to 160F. Covered the pot and rewarapped it up in the blanket for another 20 minutes.

After 80 minutes in the mash, my OG was reading 1.054. the recipe called for 1.053. however, I may have forgotten to let the sample cool before taking the reading on the refractometer.

My post boil OG reading was actually lower at 1.045. Which I realize doesn't make any sense.

 

[Evan Kingsbury]

It might be helpful if you include a little more info on your mash temps, fermentation temps and aeration techniques.
Regardless of numbers...hows the beer?

I've had this issue on 5 batches. I dumped 2 of 5 batches. And 1 is still in the carboy. Of the two batches I actually bottled- they look and taste like beer. Albeit weak and a bit too sweet.

 

[NGD]

I've had this issue on 5 batches. I dumped 2 of 5 batches. And 1 is still in the carboy. Of the two batches I actually bottled- they look and taste like beer. Albeit weak and a bit too sweet.

Sounds like either your not getting sugars broken down enough for the US-05 to eat them or your not aerating enough to allow them to propagate enough to finish the batch.

That temp swing is pretty large for US-05. Have all your batches had such large swings? I'm guessing if you were able to setting the temp in the mid 60's or even 70-72, you may get a more complete attenuation.

 

[Evan Kingsbury]

So even if I end up with a good pre boil OG reading, is it possible that my mash process may not be breaking down the sugars well enough for the yeast to consume it?

Thanks again!

 

[Muff]

I use us-05 in Michigan and my basement has been in the low 60s and my yeast has been very happy

 

[parrothead64]

I think your problem is temp fluctuations. That one gallon batch is going to fluctuate more than a 5 gallon batch in the same area. Maybe you could get a big plastic container that you could fill with water to help keep more consistent temp. Also, are you rehydrating the yeast?

 

[flars]

A mash temperature of 160°F could create unfermentable sugars. What was the temperature of the mash at 20 or 30 minutes?

 

[chickypad]

After 80 minutes in the mash, my OG was reading 1.054. the recipe called for 1.053. however, I may have forgotten to let the sample cool before taking the reading on the refractometer.

Are you using a refractometer on the fermented beer? If so are you correcting for the presence of alcohol?