Hi - long time Brewfather user here trying to ‘dial in’ the profile to more accurately predict FG. I have been analyzing the data from the past fifty or so batches, and my final gravity is consistently lower than predicted. For example on one batch it came in at 1.048 for the OG verses a predicted 1.047, but the FG came in at 1.009 vs 1.011.
I realize that this is indicative of too low a mash temperature which generates more fermentable sugars, but I have gone to great lengths to monitor and maintain the mash temperature which is spot on. In addition I monitor and control the Mash pH which is spot on at 5.40.
is there something in the Brewfather profile I can change to allow for the fact the fermentation is more efficient than predicted?
I use a full volume eBIAB, recirculate during the mash and ferment in a temperature controlled conical.
Your mash thermometer might be a little off. If you are actually mashing a few degrees cooler than you thought, it could increase the fermentability of your wort. Check your mash thermometer in both ice water at 32 F and boiling water which will boil at various temperatures depending on your elevation above sea level – you need to look up the boiling point for your particular elevation. You might find it doesn’t actually read exactly 32 F or boiling point accurately, which by interpolation will suggest that your mash temperature might be a little off as well. I know mine is off a little on my mash thermometer at both ends. Yours might be too.
YEAST selection also is probably even the GREATER factor. What yeasts are you using? I might be able to help if I know what your favorite yeasts have been. Some particular strains, such as for example US-05, attenuate far more than their counterparts such as WLP001 or 1056. Not all “equivalent” yeasts are actually equal. In any case, I doubt Brewfather adjusts attenuation based on actual yeast selected. For instance, if you select Belle Saison yeast in the software… if it doesn’t come up with FG 1.002 then it’s just plain bogus because I GUARANTEE you, Belle will ALWAYS end up at exactly 1.001-1.003.
Your hydrometer could very likely also be a little off. When is the last time you checked it in plain water? Does it actually read exactly 1.000 or is it actually like 0.998? And are you reading from the top or from the bottom of the meniscus?
Thanks Dave. That was my first thought but I have calibrated it with two Thermoworks thermometers. I normally set the mash tun temperature 2 -3 degrees higher than the mash temperature. That is how much temperature is lost in pulling the wort out from below the false bottom, where the element is, through the tubing and pump and up to the top of the mash. I have a Locline that dumps the hot wort to the top of the mash and I have used the Thermoworks Dot to monitor the mash temp in different parts of the mash. You can see in this example that the mash temperature is set to 150F, the controller at the instant the photo was taken is at 149.6F and the Dot probe is at 150F in the centre of the mash.
To be fair, I haven’t done that. The lowest temperature was 62F and I ramped it from there up to 212F and the Thermoworks and Blichmann sensors were aligned.
OK…. now… what if I told you… you’re not mashing at 150 F, but actually mashing at about 148 F? The thing is… I just noticed you have your location listed as Bucks County, PA. The elevation there is about 500 to 1000 feet above sea level. So, water does not boil at 212 F in fact but actually boils at 210 to 211 F most likely. This means… if your thermometer reads 212 F in boiling water, you need to SUBTRACT a degree or two for accurate results. So… at 150 F, you are probably ACTUALLY at 149 F, and maybe even 148 F.
It is worthwhile to also measure ice water because you might find there that it doesn’t read exactly 32 F either. And this is very easy to do. A worthwhile thing in my opinion to get the full picture of how your thermometer is reading.
Good points. I haven’t done taken the elevation into account. I am at 355’ elevation and water boils at 211.6F so that is what I calibrated to. (I’m am engineer so pretty precise!). This has been happening not just one batch but something like 100 batches using different yeasts so I don’t think it’s that. This particular batch is an English Bitter and used Wyeast 1968 with a starter. The gravity is as measured on an EasyDens so four figures of precision and I check that regularly with a good (Brewing America) conventional hydrometer. The pH is measured with a Milwaukee MW102 pH/Temp meter which is calibrated before each batch.
I will calibrate in ice water today and report back.
I conducted a calibration run this morning and the results are below. Note that the Brew Commander’s calibration of 1.9F was removed for the test. When that correction is added back in, the temperatures are within a degree. I was unable to get to 32F to start the calibration, so it starts at 38.5F.
Very cool. You certainly have some good consistent thermometers. Still you should see what they read in ice water – that still matters.
I’d also be interested in what your EasyDens and hydrometer read in plain room temperature water. Is it really exactly 1.000?
The only other thing I can think of that can consistently impact attenuation regardless of yeast is the total mash time, and what I really mean by that is the total contact time between malt and water/wort until it hits 170 F. If you are step mashing or doing a long sparge or have any dead time in there, such that the malt is hanging out in mash temperature range for longer than say 90 minutes… this can increase attenuation / reduce FG if done consistently. I know some people mash for 60 minutes then immediately bring to a boil, while others take their sweet old time or have very slow heatup like 110VAC electric instead of 220VAC or big propane. Personally… I only mash for 45 minutes typically, opposite end of the spectrum, but it’s always worked well for me on my system. So obviously, brewers vary with how much contact time there is in the mash temperature regions of 140-something F to 168 F. So, I’d be curious to hear about your average total mash time including every step up to and including mashout around 168-172 F.
I agree about the mash time. A couple of years ago my FGs were consistently a bit low, so I changed my mash schedule. Now I do 40 mins at the initial temperature (148 F - 152 F, depending on the recipe), then ramp to 162 F over 10-15 mins (120 VAC) and rest at 162 for 20 mins before raising to 170 F and removing the bag of grains. My FG is now very reliably predictable within a point or so.
Next I checked the gravity using RO water. The conventional hydrometer read about 0.990 but there was +0.7 on the temperature correction so 0.997. The EasyDens read 0.9998 so good correlation there.
I do think you may be onto something with the mash time though. For no real reason other than I can, I typically do a Mash Out at 168F which is not needed from what I have read with BIAB. This extends the mash time to maybe 90 minutes. The beer that I am using as the keystone for this question was a Best Bitter which had a 60 minute mash at 152F followed by 15 minutes at 167F. The total mash time was probably in excess of 90 minutes. I wasn’t thinking this would make for more fermentable sugars and a lower final gravity, but maybe it does.
I think I’ll try a batch without doing a mash out and see if that improves the final gravity.
So what this means is that this conventional hydrometer, which you have used to check all your other hydrometers, is consistently reading about 3 points low! That’s significant. If you have been taking the readings from this hydrometer at face value, and/or using it to calibrate your other hydrometers(!), then that can cause your issue right there, because your FG 1.009 was actually 1.012, and your OG 1.048 was actually 1.051. So, your attenuation was not actually (48-9)/48 = 81%, but rather (51-12)/51 = 76%, which is closer to “normal” attenuation. AND, there’s a chance ALL your other readings were off using any of your other hydrometers IF you used this conventional hydrometer as part of the calibration process for any of those hydrometers!
In calibration of ANYTHING… what do you trust the most? Which one? Why? The only correct answer, honestly is: THE ONE THAT READS CORRECTLY IN PLAIN WATER AT A SPECIFIC TEMPERATURE. That’s it. That’s the one to trust over any others, no matter how much you paid for them, or how many significant digits they read out to, or anything else.
Mashout can affect your efficiency and fermentability (attenuation) in a meaningful way if the crush of the malts was not great. But with a good hard crush, you shouldn’t need to mash out at all, just send the wort straight up to the boil, and you probably wouldn’t notice any difference in gravity parameters or quality of the finished beer. Crush until you’re scared, or until your runoff gets stuck, whichever is more limiting. If you don’t have quite a bit of flour in your crush (like 5-10% of the grist, maybe more), and if every kernel doesn’t break into at least 6 pieces or thereabouts, then I’d say you might not be crushing hard enough.
But yeah. In any case, mashing for less total time will raise up your FG by a point or two.
Now I have gained confidence in the EasyDens reading after 15 or so batches, I don’t use the ‘conventional’ hydrometer and more, and I mis-read it.
As you can see from the photo, the reading is way above 0.990 and the bottom of the meniscus, which is where this should be read, is just about on the 1.000 line.
The correction factor I incorrectly stated as 0.7. It is actually 0.0007.
I used the floating hydrometer for 15 years or so but now I use the EasyDens, my scale reading skills have been lost!
Good discussion. I do crush it pretty fine but can go finer. I use a Spike power mill and it’s set to 0.030” at the moment. My Mash Efficiency on the latest batch was 73% which is what I have the profile set to in Brewfather. The batch before was 79% and the one before that was 72%. My average 2025 efficiency was 78%.
I’m brewing a Kolsch tomorrow and will skip the mash out and report back.
Now I have gained confidence in the EasyDens reading after 15 or so batches, I don’t use the ‘conventional’ hydrometer and more, and I mis-read it.
There are two reasons that I spent a ridiculous amount of money on the EasyDens:
Extremely small sample size compared to a conventional hydrometer
I can easily read the darned thing! Between dark / muddy samples with bubbles and my aging eyes, I really felt that my interpretation of the hydrometer was not what it was actually trying to tell me.
