Low Original Gravity

[Johnsfolly]

Brewed my 29th extract recipe, a vanilla porter, I hope. I was disappointed in my OG reading. When I racked to the secondary on day 10, I was surprised I wasn't closer to my expected FG. Here's my story and your ideas or tips will be gratefully received:

I used 8# of pale LME in about 2-3 gallons of water.
I steeped 1# of specialty grains in the brew kettle at 165'F for 30 minutes, added the LME and boiled vigorously for 60 minutes with hops additions per the recipe.
I transferred to a 5.5 gal carboy, added 2.5 gal of RO water to bring me to 5 gallons of wort total.
I was expecting an OG of 1.038 but only got 1.020 corrected to 60'F.
I used SafeAle S-04, 1 envelope, and started it for about 7 hours in boiled water and a bit of LME. It looked like healthy growing yeast.
I pitched at 70'F, set my warming pad at 67'F.
The next day, I had a nice fermentation going.
That night, my airlock was spewing and I had wort all over the floor.
Switched to an overflow tube running into a quart mason jar of water. That overflowed.
Switched to a 1/2 gallon mason jar. This was great fermentation to my ears!
By day 10, it looked like most of the fermentation was done.
Racked to the secondary leaving virtually all of the trub behind and took a SG reading and got 1.020.
Increased the temp of the secondary to 69'F.
I get a bubble-- maybe 3-4 per minute, and I can be patient.
BTW, at transfer into the secondary, I drank what was in my hydrometer flask and it tasted clean but a bit sweet for a porter.

Looking through my logbook, I notice that I often get OG's way lower than what the recipes called for-- like it calls for 62 and I get 38 on my hydrometer. And I sometimes get higher FG's, 15 or 16 instead of the expected 10 prior to kegging or bottling.
Questions:
1. What would account for this?
2. What can I do differently?
3. How can I measure the OG out of a hot kettle when I'm not able to do a full 5-gallon boil?

Thanks in advance!

 

[IslandLizard]

I was disappointed in my OG reading. [...]

I transferred to a 5.5 gal carboy, added 2.5 gal of RO water to bring me to 5 gallons of wort total.
I was expecting an OG of 1.038 but only got 1.020 corrected to 60'F.

It's likely that your wort and top-up water weren't mixed thoroughly when you took the sample.

The OG of extract brews tend to be spot on at their target volume, unless you spilled/lost wort, or left wort behind in the kettle.

BTW, I moved your post into its own thread.

 

[IslandLizard]

When I racked to the secondary on day 10, I was surprised I wasn't closer to my expected FG.
[...]
added the LME and boiled vigorously for 60 minutes with hops additions per the recipe.

Your higher than expected FG may well be due to boiling all the extract for an hour in a relatively small volume. That volume becomes even smaller due to boil off during the hour (evaporation). Especially at such a high gravity/concentration, the sugars from the extract may caramelize, causing it to become less fermentable.

To avoid that, add only half or even less of your extract before the boil. Then at flame-out (heat being turned OFF) add the remainder. Stir well until it's all dissolved, then chill and transfer to your fermenter. Then top up with water to your batch volume. Stir well again to homogenize it, before taking a hydrometer sample.

I can recommend reading How to Brew, 4th Ed. by John Palmer.

 

[camonick]

Have you checked the calibration of your hydrometer? And what are you using to calculate your OG? 8# DME in five gallons with steeping grains should be at or above 1.070. Is your hydrometer a beer hydro. There is something way off here.

 

[IslandLizard]

8# DME in five gallons

He used LME, so ~18% less gravity than from DME:

I used 8# of pale LME in about 2-3 gallons of water.

But yeah, 8# LME in 5 gallons should yield an OG of 1.059 (8 lbs * 37 pts / 5 gallon = 59 points/gallon). Not counting the contribution from the steeped malts.

 

[camonick]

He used LME, so ~18% less gravity than from DME:

But yeah, 8# LME in 5 gallons should yield an OG of 1.059 (8 lbs * 37 pts / 5 gallon = 59 points/gallon). Not counting the contribution from the steeped malts.

Whoops, I misread that. Numbers still don’t make sense.

 

[BrewnWKopperKat]

I drank what was in my hydrometer flask and it tasted clean but a bit sweet for a porter.

Carbonation will likely have a positive impact on the tate.

I'll assume the recipe was adjusted for a concentrated boil. High OG worts require more hops to get the same estimated IBUs. Also , the "top up" water will dillute the IBUs.

BTW, I moved your post into its own thread.

Good call. I saw where the original was posted.

the sugars from the extract may caramelize, causing it to become less fermentable.

Your higher than expected FG [1.020] may well be due to boiling all the extract for an hour in a relatively small volume. That volume becomes even smaller due to boil off during the hour (evaporation). Especially at such a high gravity/concentration, the sugars from the extract may caramelize, causing it to become less fermentable.

The dreaded FG 1.020 (higher than expected) with extract. Concentrated boil makes wort less fermentable. Makes sense.

 

[D.B.Moody]

I used 8# of pale LME in about 2-3 gallons of water.

I was expecting an OG of 1.038 but only got 1.020 corrected to 60'F.

By day 10, it looked like most of the fermentation was done.
Racked to the secondary leaving virtually all of the trub behind and took a SG reading and got 1.020.

Expecting only 1.038 from 8# of malt is low.

Don't you find it strange that after your "great fermentation" you were still at 1.020. Your first reading is obviously wrong. (And why are you bothering to take readings while there are still bubbling in the airlock?)

If you were planning on racking to a secondary, why did you do the primary in a too small carboy instead of a big, cheap plastic bucket? (BTW: I'm not against using secondaries. I do it almost all the time to good effect.)

 

[davidabcd]

I've done tons of 3 gallon boils with even more LME and/or DME and I've never failed to hit the kit OG. I do stir often so nothing collects on the bottom of the pot. Simmering is just fine and you don't need a rolling boil.
As mentioned above, I think there's something off with the measurements but I don't know exactly what since I don't how you're measuring gravity.
As mentioned, get a 7.9 gallon fermenter so you won't need a blow off tube or waste beer.
Just pitch two packs of SO4 next time, skip the starters.

 

[Johnsfolly]

If you were planning on racking to a secondary, why did you do the primary in a too small carboy instead of a big, cheap plastic bucket? (BTW: I'm not against using secondaries. I do it almost all the time to good effect.)

I typically use a 5.5 g carboy for the primary and a 5 g one for secondary. And the primary had what I thought was plenty of head space for the fermentation...but I was wrong. (As I am about many things)!

 

[_BullDog_]

What are you using for Sg measurements? If a refractometer you need to make adjustments after fermentation.

 

[Johnsfolly]

What are you using for Sg measurements? If a refractometer you need to make adjustments after fermentation.

I have been using a hydrometer and correct for liquid temperature. I just bought a refractometer on sale but it needs to be calibrated at 68 deg F ambient temperature and in Michigan January, nothing in my house except my carboy ever get to 68 degrees.

 

[pdhirsch]

As a complete wild guess... you've mentioned temperature correction several times. How big of a correction do you generally make? At almost any reasonable fermentation temperature, the adjustment should be just a few points (i.e. 1.050 becomes 1.049 or 1.052 -- something small like that). If your temperature adjustments are at all significant (i.e. measure 1.050 and correct to 1.035), you may be using an incorrect adjustment formula.

 

[bracconiere]

Switched to a 1/2 gallon mason jar. This was great fermentation to my ears!

Whoops, I misread that. Numbers still don’t make sense.

i agree.an OG of 1.038, i don't ever brew...but if i did, wouldn't think i'd have to put on a 1/2 gallon mason jar?