OG too low, looking for opinions

[mr_lahey]

Hi,

This is my second all grain batch. I followed BierMuncher's OktoberFAST recipe.

Pre-boil SG: 1.042
Post Boil OG: 1.048
Target OG: 1.053

Pre-boil vol: 8.25 gal (Brewfather estimate was 7.98 gal)
Post-boil vol: 6.25 gal (Brewfather estimate was 6.25 gal)
Fermenter vol: 5.5 gal (Batch size is 5.5 gal)

Target was calculated at 1.053 by Brewfather for a ABV of 5%. I made sure to correct for temperature whenever I took any grav readings. My pre-boil SG was bang on to Brewfathers calculation even though I had too much pre-boil vol, and my boil off was more than calculated which ended up hitting the BF calculated post-boil volume almost exactly.

I imagine it has something to do with my pre-boil volume. Although I am confused as to why my pre-boil SG reading was correct.

Any ideas why my post boil OG is 5 points off? Should I add DME to bring up to target or just let it be?

Thanks

 

[Tobor_8thMan]

Grain crush, mash temp, has length and pH impact the OG.

Was the grain crush good?

What was the mash temp?

Mash length?

Mash pH? We normally want between 5.2 and 5.6 (although some say less then 5.6 and some say more than 5.6)

 

[mr_lahey]

Grain crush, mash temp and pH impact the OG.

Was the grain crush good?

What was the mash temp?

Mash pH? We normally want between 5.2 and 5.6 (although some say less then 5.6 and some say more than 5.6)

The crush looked good, compared to pictures i've seen on here.

Mash temp was 156 for the whole 45 minutes.

Mash pH was ~5.37 as calculated through Bru'n Water

Thanks

 

[Tobor_8thMan]

The crush looked good, compared to pictures i've seen on here.

Mash temp was 156 for the whole 45 minutes.

Mash pH was ~5.37 as calculated through Bru'n Water

Thanks

OK on the crush.

156 will give a full body.

Can't trust Bru'n Water's estimate. Can only know with a pH meter.

Mash length?

 

[Tobor_8thMan]

Although, re-reading the original post 1.408 vs 1.053 -- no one will notice. Remember too malster specs change. Unless we're diligent (aka anal) in updating the malt info, the OG is just an estimate.

 

[mr_lahey]

Can't trust Bru'n Water's estimate. Can only know with a pH meter.

Mash length?

Ok, I'll have to get a pH meter before my next brew.

Mash length was 45 minutes, followed by 5 minutes of vorlauf and then batch sparged.

 

[Tobor_8thMan]

The mash length and mash out sound good.

Getting a pH meter opens another whole can of worms. Perhaps, brew a few more, compare results and then purchase a pH meter?

 

[Tobor_8thMan]

"Pre-boil vol: 8.25 gal (Brewfather estimate was 7.98 gal)" IMO, 8.25 vs 7.98 is insignificant.

 

[mr_lahey]

Ok, thats all great info. Thanks Tobor.

I'll leave it be and see how it turns out. Smells and tastes awesome so far

 

[Tobor_8thMan]

Remember OG vs FG only impacts ABV. If our beer is designed, for example, 5.6% ABV, but ends up at 5.2% ABV whom but us will know?

 

[Tobor_8thMan]

BTW, had a good chuckle when I noticed the "I am the liquor". Is this a play on the Beatle's "I Am The Walrus"?

 

[mr_lahey]

BTW, had a good chuckle when I noticed the "I am the liquor". Is this a play on the Beatle's "I Am The Walrus"?

I am the liquor

Mr Lahey from Trailer Park Boys

 

[Holden Caulfield]

Your kettle points don't add up...

42 x 8.25 = 346.5
48 x 6.25 = 300

Your recipe predicts 331 points.

If your hydrometer is accurate, then your measured volumes are not accurate, so it is difficult to assess whether you exceeded, met or missed your expected efficiency.

Also, what was your grain bill and expected efficiency so that your expected points could be assessed for reasonableness?

Regards,

KB

 

[mr_lahey]

Your kettle points don't add up...

42 x 8.25 = 346.5
48 x 6.25 = 300

Your recipe predicts 331 points.

If your hydrometer is accurate, then your measured volumes are not accurate, so it is difficult to assess whether you exceeded, met or missed your expected efficiency.

Also, what was your grain bill and expected efficiency so that your expected points could be assessed for reasonableness?

Regards,

KB

Malts (11 lb 10.5 oz)
4 lb 2.5 oz (35.7%) — Weyermann Bohemian Pilsner — Grain — 2 SRM
2 lb 8 oz (21.5%) — Maker's Vienna 4.5 Malt — Grain — 4.8 SRM
2 lb (17.2%) — Maker's Munich 20 Malt — Grain — 19.5 SRM
1 lb (8.6%) — Cargill Caramel Malt — Grain — 20 SRM
8 oz (4.3%) — BestMalz Biscuit — Grain — 25.5 SRM
8 oz (4.3%) — Briess Caramel Malt — Grain — 40 SRM
8 oz (4.3%) — Briess Carapils — Grain — 1.5 SRM
8 oz (4.3%) — Great Western Melanoidin — Grain — 30 SRM

70.8% efficiency
Batch Volume: 5.5 gal
Boil Time: 90 min
---

Regarding your point about measurements being off. I wonder if it has something to do with measuring volume at different temperatures. The 8.25 gal pre boil would have been hot from the mash/sparge. The 6.25 gal would have been measured so after already cooling it down after the boil. I drop my immersion chiller in with 15 minutes left on the boil, and run it right at flame out, so I didn't really get a chance to see the volume after the boil was complete, until after I remove the chiller

 

[Holden Caulfield]

Regarding your point about measurements being off. I wonder if it has something to do with measuring volume at different temperatures. The 8.25 gal pre boil would have been hot from the mash/sparge. The 6.25 gal would have been measured so after already cooling it down after the boil. I drop my immersion chiller in with 15 minutes left on the boil, and run it right at flame out, so I didn't really get a chance to see the volume after the boil was complete, until after I remove the chiller

Most hydrometers are calibrated for 60f, so your gravity measurements are very inaccurate. For example, if you measure 1.042 at 120 degrees, your wort's gravity is actually 1.052.

Do you know the temperature of your cooled wort? If so, you can use one of the online calculators to determine your actual OG.

Also, given the inaccuracy of your pre-boil gravity reading and post boil volume, it is not possible to determine exactly how many points were actually extracted, so you don't know if you hit, missed or exceeded your target mash efficiency. That being said, searching for an answer (crush, ph, etc) to a problem that may not exist is futile. At this point, my thoughts are to assume you had a perfect day and just be ready to accurately assess your pre-boil gravity and volume, and cooled wort OG and volume for next time. Your beer will taste great.

Going forward, you should cool your wort to 60 degrees before checking gravity. Also there are many online temperature adjustment calculators in case your test sample is warmer. Another option is to get a refractometer which only needs a few drops of wort to test gravity, which can be cooled quickly in a glass that has been refrigerated. You only need to boil your chiller 2 or 3 mins which should enable you to check the boil volume right at the end. It is also helpful to know the volume the chiller occupies as this can be subtracted if difficult to read the volume during the boil.

As far as your grain bill - 11.6 pounds of grain for a 6.25 batch should get you in the 1.053 range with reasonable efficiency.

KB

 

[Vale71]

Regarding your point about measurements being off. I wonder if it has something to do with measuring volume at different temperatures. The 8.25 gal pre boil would have been hot from the mash/sparge. The 6.25 gal would have been measured so after already cooling it down after the boil. I drop my immersion chiller in with 15 minutes left on the boil, and run it right at flame out, so I didn't really get a chance to see the volume after the boil was complete, until after I remove the chiller

The correction factor at mash temp is 0.98 at boil temp 0.96.
This would place your corrected pre-boil volume at 8.08g (8.25X0.98). With your measured evaporation your FG should be at 1.054 instead of 1.055 which still does not match your measurements by a wide margin, meaning there must be one or possibly more uncorrected measurement errors.

 

[mr_lahey]

My gravity readings were all corrected to temperature (68f) using brewfathers correction tool:

My hydrometer is calibrated to 68f/20c. I verified it with water before I started.

It was the volumes that I was speaking about that weren't corrected to any kind of specific temperature.

 

[mr_lahey]

The correction factor at mash temp is 0.98 at boil temp 0.96.
This would place your corrected pre-boil volume at 8.08g (8.25X0.98). With your measured evaporation your FG should be at 1.054 instead of 1.055 which still does not match your measurements by a wide margin, meaning there must be one or possibly more uncorrected measurement errors.

Thanks for that info.

Yea I thought I was careful about my measurements, which is why I am confused about the numbers not working out. But It is starting to look like maybe I messed up somewhere.

 

[Kickass]

I am the liquor

Mr Lahey from Trailer Park Boys

WAY off topic, but I named my last IPA Recidivist IPA (where Amarillo, Columbus, and cascade continued to offend at a rate that would make Ricky, Julian and Bubbles proud) after Mr. Lahey’s comment to Randy about the boys being recidivists.

I couldn’t help, sorry for the distraction from the thread.

 

[VikeMan]

Most hydrometers are calibrated for 60f, so your gravity measurements are very inaccurate.

In the last decade or so, I've seen a lot more calibrated to 20C (68F) than anything else. Unfortunately, there are lots of outdated web sites that refer to 60F (or 59F), without even mentioning that hydrometers with other calibration temperatures exist. At any rate, @mr_lahey the calibration temp is normally printed on (in) the hydrometer.

 

[Tobor_8thMan]

Look at the hydrometer. After reading this thread I checked my hydrometers. 2 of 3 had the calibration temp printed on the paper inside the hydrometer. Time to throw out the 3rd one.