Low final gravity question

[Muchacho]

Lately I have been getting extremely low final gravities and am looking for suggestions as to what might be going on. A couple of batches have tasted thin and lacking in flavor/body. Recently, they have tasted fine, but I am getting crazy high attenuation based on the yeast’s ranges. A lot of these have been mashed at relatively low temps, but it is hard for me to imagine that would have such a dramatic effect. I have been shaking the carboy to oxygenate (but just treated myself to a pump and stone). The gravities were measured with a hydrometer and I use the temp correction in BeerSmith.

Here are some recent examples.

BierMuncher’s Centennial Blonde. Followed the recipe, but upped the 2row to account for my efficiency. The mash temp was lower than planned. Final temp was probably around 146 before mashout. OG 1.044, finished at 1.004. Fermented with wyeast American Ale II that was 3.5 months old with a 1L starter (should have been about right per Mr. Malty). Temp 65 -> 69 for ~5 days before cold crash. ~90% attenuation. Tastes great.

FATC1TY’s Oddsides clone. Mashed ~150. OG 1.057. FG 1.005 with pacman yeast @ 64. Put ~ 200 ml harvested slurry into a 1L starter. Works out to be something like 90% apparent attenuation. Tastes great.

A basic saison went from 1.054 -> 1.002, but this was mashed low and I used WY3711. But the attenuation is really high 96%! Tastes great.

Simple American wheat 1.038 -> 1.003 with pacman. 91.8% attenuation in 5
days. I mashed low @ 150. Had no body, like water and had little flavor.

Any thoughts?
Thanks!

 

[Nike_Eayrs]

I am curious as well. I had a similar situation where two batches went down that far. Still drinkable, but all I taste are hops. No real body at all.

 

[hunter_le five]

Have you calibrated your thermometer / verified that it is reading temps accurately? Maybe you are mashing at lower temps than you realize and are getting more fermentable sugars than you want?

 

[eltorrente]

Yeah, are you sure your thermometer is accurate?

Buy a calibrated digital one - these are indispensable. I got one for around 20dollars, and it came with a calibration certificate. If you are an all-grain brewer, you MUST have an accurate thermometer.

 

[duboman]

Well, considering that you admitted to mashing low in each scenario you have answered your own question and I might assume that your thermometer is off and you are actually mashing lower than you think you are

Low mash temperatures create a much more highly fermentable wort which then results in greater than average attenuation. Calibrate your thermometer and raise your mash temperatures accordingly and your % of attenuation will drop.

 

[Yooper]

If I mashed a beer, especially one with adjuncts and no less fermentable ingredients like dark crystal, at 146- I'd finish at 1.002-1.005 or so.

I made an IPA with two-row, a pound of corn sugar, and a pound of rye at 147, and it finished at 1.006!

I know my thermometer is dead on, but if I would have mashed lower, the beer would have been drier. If your thermometer is even two degrees off, you could be mashing in the low 140s for the one that was mashed at 146.

 

[Muchacho]

Thanks every one.
I use a new thermapen that came with a certificate. I will check it against boiling H2O to see if it is really calibrated.
I guess that I did not realize that mash temp has that big of an effect on the final gravity. I figured that it was more of a fine point rather than something that can totally alter the net result. Thanks for straightening me out.