Missed OG... why?

[andy6026]

On Saturday I brew "Pliney the Elder" with a target OG of 1.072. My actual pre-pitching OG was 1.062. While everything seemed to go smoothly according to the recipe, I'm curious as to why I missed the OG by that much.

The recipe is posted below, but the basics are as follows. We weighed the grains carefully. We mashed at 151 F for 60 mins and it held that temp consistently. I mashed out at 170 as it says. We then did a 90 minute boil and added the hops according to the recipe. I the aerated the wort for several minutes with a drill and paint stirrer before using a turkey baster to take samples from the middle of the fermener to measure the OG. I assume my aerating also gave it a decent enough mix to take an accurate OG reading?

I know Charlie's book says that those new to AG ought to add extra grains as they won't likely hit their expected OG otherwise... but why? It's not like the grain says, 'haha, this guy's new... I'll fool him". There must be something I (and other newbs) are doing to impede us from hitting the target OG. Any clues?


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Recipe:

for 6.0 gallons (22.7 L) [Net: 5 gallons (18.9 L) after hop loss]
13.25 lb (6.01 kg) Two-Row pale malt
0.6 lb (272 g) Crystal 45 malt
0.6 lb (272 g) Carapils (Dextrin) Malt
0.75 lb (340 g) Dextrose (corn) sugar
3.50 oz (99 g) Columbus* 13.90% A.A. 90 min.
0.75 oz (21 g) Columbus* 13.90% A.A. 45 min.
1.00 oz (28 g) Simcoe 12.30% A.A. 30 min.
1.00 oz (28 g) Centennial 8.00% A.A. 0 min.
2.50 oz (71 g) Simcoe 12.30% A.A. 0 min.
1.00 oz (28 g) Columbus* 13.90% A.A. Dry Hop (12 to 14 days total)
1.00 oz (28 g) Centennial 9.10% A.A. Dry Hop (12 to 14 days total)
1.00 oz (28 g) Simcoe 12.30% A.A. Dry Hop (12 to 14 days total)
0.25 oz (7 g) Columbus* 13.90% A.A. Dry Hop (5 days to go in dry hop)
0.25 oz (7 g) Centennial 9.10% A.A. Dry Hop (5 days to go in dry hop)
0.25 oz (7 g) Simcoe 12.30% A.A. Dry Hop (5 days to go in dry hop)
*Tomahawk/Zeus can be substituted for Columbus
White Labs WLP001 California Ale Yeast or
Wyeast 1056 American Ale Yeast
Original Gravity: 1.072
Final Gravity: 1.011
Extract Efficiency: 75 percent
IBUs: 90-95 (actual/not calculated)
ABV: 8.2%
SRM: 7
Directions
Mash grains at 151-152° F (66-67° C) for an hour or until starch conversion is complete.
Mash out at 170° F (77° C) and sparge. Collect 8 gallons (30 L) of runoff, stir in dextrose,
and bring to a boil. Add hops as indicated in the recipe. After a 90 minute boil, chill wort
to 67° F (19° C) and transfer to fermenter. Pitch two packages of yeast or a yeast starter
and aerate well. Ferment at 67° F (19° C) until fermentation activity subsides, then rack
to secondary. Add first set of dry hops on top of the racked beer and age 7-9 days, then
add the second set. Age five more days then bottle or keg the beer.

 

[rodwha]

It's said that as long as you followed the recipe and it was an extract then you hit the numbers close enough. It's that it wasn't well stirred, and so the reading is off.

it sounds as though you did well though...

I have had the other problem in which my numbers are higher than they should be, and I've poured it in the fermentor in a way I figure should help with mixing. Then I stir it for a good while and allow to sit. I'd think the numbers should be accurate enough....So either I'm getting more out of my steeps or the calculator is off. Maybe I ought to check my hydrometer's zero...

 

[DocScott]

Sounds like you did everything well. If that's the case, a few things could account for a low OG. First would be missing volumes. If you end up with too much wort, your OG is lower. This can come from adding too much water in your mash/sparge or from misjudging your boil off rate. Maybe even a leak in your chiller.

Other thing to consider, as I think is a higher likelihood is poor conversion during your mash or not sparking correctly. Also, check the crush on your grains as well. I've found a good crush is critical for planning recipes and hitting your numbers right.

The more you brew on your system, the better you'll know it. Then you can enter your efficiencies into calculators and adjust recipes to fit your particular system. No fear though, your Pliny clone will still be delicious.

 

[andy6026]

Great, thanks guys. Judging on your responses I suspect that my water volume might have been slightly higher (I added a bit to get the mash heat up - but figured it to be an insignificant amount) AND perhaps by the way I milled the grains. It was my first AG batch so even though I'm fairly confident that it will turn out well, I was a little curious as to why it was 10 points lower. My next trouble shoot is that I may have a stuck fermentation. It was going well yesterday but the bubbles have stopped coming out my blow-off tube today. So I gave it a bit of a gentle agitation this morning, and I'll check it after lunch.

Cheers!

 

[GrantH]

Boil it down further (lose a little beer) or just add some fully fermentable sugars.

 

[DocScott]

Don't rely on the airlock to judge fermentation. Only way to know for certain is gravity readings. It is very unlikely that your ferment stalled at this point unless you dropped the temp drastically. More likely, the seal on your fermenter isn't perfect and gas is escaping somewhere else.

I think improving your crush will help tremendously improve your extraction. One of the Better things I've done (except temp control) is get a barley crusher and mill my own at a finer gap setting. Took my efficiency from 65% to 80+ %

 

[Britinusa]

As previously mentioned, different factors may be to blame for missing your OG, Poor crush, quality of the grain, whether conversion was good enough, boil volume.

 

[woozy]

Sounds like you did everything well. If that's the case, a few things could account for a low OG. First would be missing volumes. If you end up with too much wort, your OG is lower. This can come from adding too much water in your mash/sparge or from misjudging your boil off rate. Maybe even a leak in your chiller.

I'm a bit of a newbie and I've always been a bit confused by this. One thing, too much wort would account for a low S.G. at a high volume but wouldn't this be accounted for in the boil-off and in the efficiency calculator? Of course if after the boil your post-boil volume was higher then the intended then you o.g. will be lower but efficiency isn't effected by boil-off, is it? I mean, it can't be by definition, right.

Second, does pre-boil volume and/or mash volume effect efficiency? My intuition says it'd be easier to extract N bits of sugar at a low specific gravity with a lot of water than to extract the same N bits of sugar at a high specific gravity with a little amount of water. This seems to be born at that I get *slightly* higher than average efficiency when I do the no-sparge BIAB method where I mash with the *entire* pre-boil volume, turn the whole thing up to 170, and dunk and squeeze the bejezeus out of the grainees.

Also I figure if my pre-boil volume is too large, I can just add more time to the boil. (e.g. if my boil-off is a gallon an hour, my target volume is 2 gallons, but my pre-boil volume is 4 gallons, then I simply boil for an hour before adding my first hops and then boil for a second hour.) Anything wrong with that?

Anyway, I think to answer the OP's question, I would assume newbies like myself tend to fail to keep a constant temp, hence the enzymes don't germinate completely (less sugar) and we probably sparge too quickly. At least that seems .... plausible.

 

[andy6026]

Ah, sparging too quickly might have contributed to my low OG. I essentially used a 2 quart pitcher to pour in the sparge water and I tried to introduce it to the mash-tun at about the same rate the wort was coming out at the bottom. Should I be slower?

 

[DocScott]

Woozy, what you propose is what I meant. Too much volume post boil will yield a lower OG reading. I was simply suggesting areas where the volume could increase if you aren't paying attention. If you know your volume is high Pre boil, then yes, you can boil longer/harder to boil off the excess volume and end at the correct gravity.

I'm on my phone app so referencing your other question is challenging, but I think you asked about improved extraction by using more water. Yes, it should. This is basically the idea of getting better extraction with different sparge techniques. See palmers book for details if you're interested in learning more. The sugars in solution will be extracted until an equilibrium is achieved. Adding more water allows more sugars into solution but this is not a linear relationship. Therefore you'll reach a point where adding another volume of water will extract more sugars, but is it worth it in terms of later having to boil the extra volume out. On a homebrew scale, most of us vote no, and just add a few more oz of grain to compensate.

 

[rodwha]

I thought it was ideal to use ~1.5 qts/lb of grain, and that going over that volume isn't good?

For steeping I haven't worried about the volume, but I've been considering doing more BIAB, and it just seems easier and quicker to start with 3.5 gals in my 5 gal pot and "sparging" with 2 qts after that hour to get me to 4 gals. Instead of say 2 gals at 1.5 qts/lb and then having to add another 1.5 gals, which would take longer to bring to boil.

 

[DocScott]

I think what current literature says is that thinner mashes end up with better extraction efficiency. This is again because more sugar can be extracted. The threshold for this seems to be at 2.5 l/kg ratio. Over this, extract yield doesn't really improve much with thinner mashes. This data was determined in a no-sparge mash though, so you'd have to factor your sparge extraction to decide what's best for your system.

 

[DocScott]

If my conversions are correct, 2.5l/kg is equal to about 1.2-1.25 qt/lb

The above info comes from studies by Briggs and one by Kai.

 

[woozy]

I thought it was ideal to use ~1.5 qts/lb of grain, and that going over that volume isn't good?

That's what I read too. But then Yooper told me she uses that 2 qts/lb of grain.

So I figured I'd do

Mash = 2 qts/lb * lbs of grain
Sparge = Desired pre-boil volume + grain absorbtion - Mash

And then someone else, I forget who, told me just to to BIAB no-sparge and use full pre-boil volume plus grain absorbtion; bring the *whole* thing up to mash-out temp and pseudo-sparge (my term) by by dunking and draining the whole thing three of four times and squeezing the heck out of.

I did and my efficiency seems to be between 78 to 80%. And I seem to have calculated both my grain absorbtion and boil off spot-on, so I ended up with *exactly* the desire post volume at an original gravity some 6 points too high (the recipes ware calculated at 75% efficiency).

But, honestly, I'm too new to this and inexperienced and understand the theory so little, I don't really know what to make of this. Except that it works for me.

Part of me wants to try doing it the "right" way but then I can't help but think "why bother?"

 

[woozy]

If my conversions are correct, 2.5l/kg is equal to about 1.2-1.25 qt/lb

A liter of water weighs a kilogram. So 2.5 l/kg is a scale of 2.5 units of volume to 1 unit of volume-weight of water.

A quart of water weighs 2 pounds. So 1.25 qt/lb is a scale of 1.25 units of volume to 1/2 unit of volume-weight of water or 2.5 to 1.

Yup, they are exactly equal. (And no metric to us. conversion round-off!)

=====
or another of looking at it: 1 liter water-weight = 1 kilogram; 1 pint water-weight = 1 lb. So N liter/kilogram = N pint/lb = .5 N qt/lb.

*NEAT* this makes my little math glands ....so..... happy!

 

[ajf]

for 6.0 gallons (22.7 L) [Net: 5 gallons (18.9 L) after hop loss]
13.25 lb (6.01 kg) Two-Row pale malt
0.6 lb (272 g) Crystal 45 malt
0.6 lb (272 g) Carapils (Dextrin) Malt
0.75 lb (340 g) Dextrose (corn) sugar
Extract Efficiency: 75 percent

13.5 lbs to row at 36 points per pound = 466 pnts
1.2 lbs crystal malt at 34 point per pound = 40.8 pnts
466 + 40.8 = 526.8 * .75 = 395.1 points per lb
divided by 8 = .493875 = 1.049375 per points per lb for the malt
Now for the sugar,
12 ounces = 12 / 16 * 44 = 33 points per lbs / 6 gallons = 1.0055lbs per gallon. = 1.049865 when combined with the malt.

I don't think it is reasonable to get 1.072 out of that grain bill when you have a have a bill that you gives you a gives you a value of 1.055.

-a.

 

[andy6026]

thats interesting... if your numbers are correct then I'm lucky to have gotten 1.062. Or I didn't and my testing solution wasn't mixed properly.

 

[DocScott]

That's what I read too. But then Yooper told me she uses that 2 qts/lb of grain.

I usually use anywhere from 1-2 qt/lb on my system for what it's worth. Sorry to have taken this thread slightly off topic.

 

[ajf]

thats interesting... if your numbers are correct then I'm lucky to have gotten 1.062. Or I didn't and my testing solution wasn't mixed properly.

I'm sorry, my numbers were not correct.
It seems to me that one of my medications are causing me some major problems, in exchange for some minor problems. If I am wrong in my diagnosis then I don't want to think about what is actually happening.

-a.