Low Starting Gravity

[joegbeer]

Been brewing for 2+ years on my Grainfather system, probably 40+ brews. Recently my last 5 brews have had a significantly lower SG than expected. I thought for sure this was something I could diagnose on my own, but unfortunately I'm getting really frustrated as I haven't really figured out what is causing it (hence 5 brews with low SG).

What is bothering me is that my actual SG is pretty far off of the Beersmith recipe estimate. I really don't remember having this problem before 3-4 months ago.

My last batch was 15 lbs of Maris Otter, 1 lb of various specialty malts, 1lb of various crystal malt, 1 lb of roasted malts. 18 lbs grain bill. I use Brew'N water with distilled water for a water profile that estimated a 5.4 pH, but I do not actually measure the pH during the brew. My Beersmith recipe/equipment configuration was giving me a 1.089 SG estimate at 70% brewhouse efficiency. My pre-boil was 1.069 at 6.7 gallons and my SG was 1.073. Per the Grainfather mash efficiency calculator it is suggesting my efficiency is at 70%, but Beersmith is saying ~55%.

1) I figured it was my mill. So i re-calibrated my mill gap to .032. No improvement in the next batch efficiency.
2) I was concerned it could be an issue with freshness of the bulk grains I was using at home. Bought the next batch of grain at the LHBS. Also had them mill x2 as a feeble attempted to rule out my incompetence. No improvement in the next batch efficiency.
3) I focused on making sure my Grainfather mash recycling was not going to fast to cause the wort to drain through the overflow valve. My batch sparges have all seemed to go well, good water flow, 25 minutes or so. No improvement in the next batch efficiency.

I'm finally at maybe my beersmith configuration for my equipment was out of whack. Is a 1.073 SG for an 18lb grain bill abnormally low?

I reviewed all of the equipment settings in my Grainfather Beersmith profile against several internet threads and didn't find anything that looked wrong. Maybe I should just reload the Grainfather equipment profile and start from scratch? See how that impacts the recipe estimates?

Any other recommendations on what to look at? Thanks.

 

[FatDragon]

Been brewing for 2+ years on my Grainfather system, probably 40+ brews. Recently my last 5 brews have had a significantly lower SG than expected. I thought for sure this was something I could diagnose on my own, but unfortunately I'm getting really frustrated as I haven't really figured out what is causing it (hence 5 brews with low SG).

What is bothering me is that my actual SG is pretty far off of the Beersmith recipe estimate. I really don't remember having this problem before 3-4 months ago.

My last batch was 15 lbs of Maris Otter, 1 lb of various specialty malts, 1lb of various crystal malt, 1 lb of roasted malts. 18 lbs grain bill. I use Brew'N water with distilled water for a water profile that estimated a 5.4 pH, but I do not actually measure the pH during the brew. My Beersmith recipe/equipment configuration was giving me a 1.089 SG estimate at 70% brewhouse efficiency. My pre-boil was 1.069 at 6.7 gallons and my SG was 1.073. Per the Grainfather mash efficiency calculator it is suggesting my efficiency is at 70%, but Beersmith is saying ~55%.

1) I figured it was my mill. So i re-calibrated my mill gap to .032. No improvement in the next batch efficiency.
2) I was concerned it could be an issue with freshness of the bulk grains I was using at home. Bought the next batch of grain at the LHBS. Also had them mill x2 as a feeble attempted to rule out my incompetence. No improvement in the next batch efficiency.
3) I focused on making sure my Grainfather mash recycling was not going to fast to cause the wort to drain through the overflow valve. My batch sparges have all seemed to go well, good water flow, 25 minutes or so. No improvement in the next batch efficiency.

I'm finally at maybe my beersmith configuration for my equipment was out of whack. Is a 1.073 SG for an 18lb grain bill abnormally low?

I reviewed all of the equipment settings in my Grainfather Beersmith profile against several internet threads and didn't find anything that looked wrong. Maybe I should just reload the Grainfather equipment profile and start from scratch? See how that impacts the recipe estimates?

Any other recommendations on what to look at? Thanks.

That's a fairly low OG for that grain bill indeed, but it's also a big grain bill for a system of that size. That might have hit you for a couple points. However, more notable is the fact that you seem to have boiled off a lot less than you should have. Calculating your final volume from the gravity increase, it seems you ended up .8 gallons higher than your intended volume, and if you had boiled down to 5.5 gallons you'd be closer to 1.085, which is not so far shy of your intended OG.

 

[IslandLizard]

Estimating maximum extraction potential in points:
15# Base (MO) at 35 ppp = 525 points
1# Specialty mix at say 30 ppp = 30 points
1# Crystal mix at 34 ppp = 34 points
1# Roast mix at say 28 ppp = 28 points
Total: 617 points

At 80% mash efficiency: 617 * 80% = 494 points
494 points in an estimated post boil volume of 5.7 gallons (1 gallon boil off) is 87 points per gallon ==> Expected gravity: 1.087

You didn't mention your post boil volume, and how much wort you left behind with the trub, so numbers may be a little different.

If your mash efficiency is higher, 85% is very attainable, your gravity will be higher by an equal percentage.
So yeah 1.073 is surely on the low side.

Have you measured the mash temps during the mash with a separate and calibrated thermometer?

 

[IslandLizard]

My pre-boil was 1.069 at 6.7 gallons and my SG was 1.073

69 ppg * 6.7 gallons = 462 points

462/617 (estimated extraction potential) = 75% mash efficiency.
Not great, but higher gravity mashes can take a bit of a hit.

You say you sparged, but if you're not sparging, or not sparging thoroughly, quite a bit of high gravity wort remains trapped in the wet grain. That could have something to do with the lower efficiency and thus lower gravity than expected.

Also, from 1.069 preboil to 1.073 post boil is only a gain of 4 points, that's a pretty low boil off. Was that an hour boil? A gallon an hour is more typical, but not sure what it is with a Grainfather.

 

[FatDragon]

Also, from 1.069 preboil to 1.073 post boil is only a gain of 4 points, that's a pretty low boil off. Was that an hour boil? A gallon an hour is more typical, but not sure what it is with a Grainfather.

I was thinking the same thing. Maybe there's something that's gone wrong with the element or wiring in the last few batches and he's not getting as vigorous a boil, thus less boil-off and lower OG.

 

[joegbeer]

You didn't mention your post boil volume, and how much wort you left behind with the trub, so numbers may be a little different.

I've measured the trub and wort loss (chiller) in the past at .8 gallons. I did a boil off test a long time ago and it was .5 gallons an hour. I didn't write down my post boil volume, but I'm ball parking it at 6-6.1 gallons. I put about 5.1-5.2 gallons in the fermenter.

Have you measured the mash temps during the mash with a separate and calibrated thermometer?

No i've relied on the thermo-well and controller. Would be interesting to see if the internal mash temp is significantly different than the controller reading.

 

[joegbeer]

I was thinking the same thing. Maybe there's something that's gone wrong with the element or wiring in the last few batches and he's not getting as vigorous a boil, thus less boil-off and lower OG.

Interesting data point that I left out. My heating element died on the 3rd of these 5 batches. Grainfather graciously replaced it and I've used that element on the last 2 batches. I was actually very hopeful initially that it was a weak heating element was the problem, but it didn't pan out. However, that doesn't mean that my old controller unit isn't having trouble controlling the heating element.

 

[doug293cz]

I plugged your 18 lb grain bill, 6.7 gal pre-boil volume into my mash & sparge simulator assuming 95% conversion efficiency with single batch sparge, and came up with an estimated pre-boil SG of ... 1.069. Mash efficiency was 72 - 73% and lauter efficiency was 76 - 77%. Appears you got almost exactly what you should have gotten. OG is going to depend on boil off.

Brew on

 

[joegbeer]

I plugged your 18 lb grain bill, 6.7 gal pre-boil volume into my mash & sparge simulator assuming 95% conversion efficiency with single batch sparge, and came up with an estimated pre-boil SG of ... 1.069. Mash efficiency was 72 - 73% and lauter efficiency was 76 - 77%. Appears you got almost exactly what you should have gotten. OG is going to depend on boil off.

Island Lizard said it looks a bit low. It's good to get your perspective that it's reasonably close. Appreciate the feedback as another data point.

The most frustrating thing for me is until I figure out how to get beersmith to more closely approximate how my system is functioning (assuming I'm not screwing somethingup), it's not terribly useful for me whipping up recipes and getting my ABV/IBUs semi-accurate. Doubly frustrating that it wasn't this far off when I go back 3-4 months ago.

Side comment: I know my gravity measurements aren't significantly off as I use a hydrometer AND I have a Tilt, both reporting similar readings.

 

[thehaze]

The Grainfather will suffer - I have one - from low efficiency when using more than 14-15 lbs grains. That's just how it is due to its design and size. If you want to brew high gravity beers, you have a few options: a much smaller batch size ( sparge with less water ) and / or using sugar/DME in the boil. I have succeeded in brewing 6 gallons of 9.5% Porter, but it took some hassle, but not that much that I wouldn't try it again. However, if efficiency means something to you, brewing recipes with 18 lbs in the Grainfather will leave you dissapointed almost every time, unless you cut the sparge water in half and lower your batch size.