What went wrong?

[tjz827]

Hey guys,

I wanted to try out the Brulosophers Best Blonde Ale recipe yesterday. Grain bill is as follows:

8.25 - 2 Row
0.75 - white wheat
0.50 - Crystal 15L
0.25 - Carapils

BeerSmith estimated a pre boil gravity of 1.041 which I was very close to at 1.038. However, my post boil gravity after an hour boil only reached 1.032. (This was a sample right before I pitched the yeast.) How is that possible? Estimated OG needed to be 1.051. At any rate, I’m going to roll with it and see how it turns out, even if it is low alcohol. I’ve got a nice fermentation started as of this morning. What went wrong with my numbers do you think? What is the possible reason for not hitting gravity numbers?

 

[brewcat]

Post boil gravity was likely misread.

 

[tjz827]

Quite possibly. When boiled, your gravity is supposed to rise, correct? Because of the evaporation loss?

 

[TANSTAAFB]

Aggie math [emoji16]

 

[TANSTAAFB]

Hook 'em

 

[Lefou]

Your post-boil gravity should be higher than pre-boil gravity because the water will evaporate. If your post-boil gravity is less than predicted Original Gravity, there are a couple of ways to compensate.
One would be to add some sort of fermentable into your wort - extract, honey, or sugar - after the boil to the primary fermentor.
The second would be a bit more involved and would require a bit of math to get your brew house efficiency calculation. That means adding extra grain or extract BEFORE boiling your wort to insure extra points lost through inefficiencies from the mash.
I typically get 68-72% efficiency and will add more grain to compensate. Your estimated brew house efficiency should be unique to your setup, but can change with method and ingredients.

 

[madscientist451]

When you measured your pre-boil wort gravity, what was the temperature of the wort?

 

[tjz827]

Thanks Lefou. I’m pretty sure this is going to be the best route to go. I’ve only brewed 3 beers using BeerSmith and have tried to tweak my equipment profile to be correct whenever I make a new upgrade. I’m still working on the efficiency part. Btw, the pre boil wort I had to cool down and got a sample around 80-90 degrees if I had to guess.

 

[Lefou]

At 80-90F, you'll have to adjust for temperature on the hydrometer measurement.
At 85F and a gravity of 1.038, the adjusted value for a 68degree hydrometer should be 1.041.

If your software has a calculator it's a great reference. I have a cheap triple scale to use but have a computer nearby on brewdays to help out with the number games.

 

[govner1]

What were your pre-boil & post boil volumes? If they were on target you definitely have an issue with your SG measurements. BTW- what are you using to measure your SG? Have you calibrated?

 

[tjz827]

Pre boil volume of 7.25 gallons and ended up with around 5.75. This was about 95% on point as I have a boil off of of around 1.5 gallons per hour. I measure the SG with a standard triple scale hydrometer with a measuring cylinder. Don’t know that I’ve calibrated. Please elaborate...

 

[govner1]

Have you checked your readings against solutions w/ known values, ie, distilled water @ 68°F should read 1.000.
I cannot imagine a scenario where you reduced your volume by 1.5 gal. & your SG went down.
The only known point of error at this point has to be your hydrometer.
Was was sample tube full so that the hydrometer wasn’t touching the bottom during either measurement?

 

[tjz827]

It wasn’t touching the bottom but it wasn’t overflowing...would that make a difference? I will certainly make sure it is calibrated before the next batch. I appreciate your insights.

 

[JohnSand]

As above, you also should correct gravity readings for temperature. Hot wort will read lower. Next time check the temperature and make the corrections. If you did not correct for temperature, maybe you shouldn't add anything to this batch. In the future, correct for temperature, and keep some extract handy if you want to adjust the gravity.
Don't worry, we all make mistakes and it will still be beer. Practice will make the process easier and more consistent.

 

[govner1]

It wasn’t touching the bottom but it wasn’t overflowing...would that make a difference? I will certainly make sure it is calibrated before the next batch. I appreciate your insights.

You don’t/shouldn’t fill your cylinder to the point that it overflows or so low that the hydrometer touches the bottom. It might take a little practice w/ water to get used to your hydrometer.
Ideally you want it free floating with the level of your sample an inch or so below the rim. The point where you take your reading is called the meniscus & this is where the sample “clings” to the edge of the hydrometer.
As others have said, taking your readings at 68° or adjusting for temperatures is important for accuracy. You can always allow your sample to cool in a fridge for a few minutes if you’re dealing with hot wort. Don’t forget it or you’ll have to adjust for a lower temp.

 

[Lefou]

Doing the same recipe several times will help you get the numbers closer and improve your methods.

 

[IslandLizard]

Did you add any top up water? If so it may not have mixed thoroughly, hence giving you a low reading.

Check the fineness of your milled grain. Most LHBS mill very coarse, even letting through a large % of uncracked grain. That will result in low (mash) efficiency and thus lower gravity than calculated.
Milling twice helps, but milling on a finer gap is much better, especially when small kernel grain is included, like wheat or rye. Flaked good are usually fine as is.

 

[jalc6927]

Refractometers can be useful instead of hydrometer as well

 

[govner1]

But you still need to pay attention to the temp of your sample. ATC refractometers only adjust for the temp of the device itself, not the sample. And of course once fermentation begins the refractometer is not accurate without guessing at the amount of alcohol present and adjusting the value read.
I use a refractometer prefermentation and a hydrometer afterwards. Calibration is still needed for both.

 

[jalc6927]

I check my OG just before pitching yeast, so it’s always around 60-64 degrees

 

[JR_Brewer]

Yeah, sounds to me like you haven't corrected for measuring gravity at different temps. As temperature increases, specific gravity drops for the same liquid.