Continually Missing Target OG

[servadia]

I've been an all-grain brewer for almost a year now. I've made some very good brews and have only had a few so-so brews. What I've found is that I'm consistently missing my OG.

Last night, my target was 1.073. I ended up at 1.063. Style is American IPA. Here are some specs for my 5.5 gallon batch:

10.0 lbs 2-row
2.0 lbs Vienna
1.0 lbs Cara-Pils/Dextrine
1.0 lbs Crystal 20
1.0 lbs Caravienne

Heated strike water to 165 and hit target mash temp of 153 for 60 minutes. Ending step temp was 149.

Heated just under 5 gallons sparge to 180 with a target of 170. Ending step temp was a lowly 150 and I don't know why! This was verified with 3 different thermometers.

Volume of first runnings - 2.5 gallons
Volume of second running - 5.0 gallons
Reached target pre-boil volume of 7.50 gallons successfully!
Pre-boil gravity - 1.056 (targeted 1.053)

I used a 75 minute boil and added the first hops addition five minutes into the boil...total of 70 minutes for the bittering hops. I usually do things this way so I can take the first 5-10 minutes to skim the hot break.

I was able to put my targeted volume in the primary...5.50 gallons.
OG was 1.063. Should have been 1.073. This seems to be a consistent thing. I don't know if my times/temps are off for the mash and sparge. If they are the cause, how can I improve this step? Equipment issue? One concern I have is the mash tun. I'm using a 17.5 gallon cooler that I typically use for our 10-gallon brews. I use this same tun for my 5 gallon brews. Is this huge tun too big for the 5-gallon batches?

Hate to sound desperate but I'm getting frustrated! Thanks!

 

[Ichthy]

Who crushes your grain?

 

[servadia]

I crush my own. This is the 3rd batch crushing my own and surprisingly, I'm getting better results since I've been crushing my own instead of the LHBS doing it.
Side note...I share the grain mill with a friend. He seems to be doing OK on his side of the brewing world. Thanks for the reply!!!

 

[Ichthy]

Have you calibrated your hydrometer and are you temp correcting your readings?

 

[servadia]

Yes. The OG's that I posted are corrected for temperature. Hydrometer is good also. Thanks again!

 

[Ichthy]

Are you mashing too thin and not sparging with enough water? What is the water/grist ratio?
Is there a lot of dead space in your tun?
Are you using a manifold or braid?

 

[Ichthy]

HMMM.... I'm not real sure. Maybe you should take detailed notes when brewing with your brother. Or have him 'supervise' your brew session.

If you hit your preboil volume you must not be boiling down enough. The only reason I say this is that if all the sugar you want in the kettle is there to begin with (i.e., your preboil gravity is correct) the only why to change your OG is by boiling down to a volume. Is your software not accurately accounting for post boil volume?

 

[Dave258]

Did you ever try to break your sparge into 2 equal amounts instead of one big sparge? It seems that I get better efficiency when I do this.

 

[servadia]

Never tried that. So how would I go about that? My sparge volume was about 5 gallons for 15 minutes at 170. Thanks!

 

[Dave258]

Just divide it in half. 2 sparges of 2.5 gallons each. I usually let each round sit for 10 mins before I vorlauf and drain. Not saying it will solve everything, but might help.

 

[servadia]

Cool. I'll try that. Thanks!!!

 

[kanzimonson]

Lemme get this straight: your preboil gravities suggest that your beers are on target, right? In your above example, you had 7.5gal of 1.056 wort. If you boil that down to 6gal, you'd have 1.070. That's pretty close to the target of 1.073 so let's just say that up until the beginning of the boil everything was fine.

That suggests that none of this is an efficiency problem. You can effectively ignore all this crap about different water/grain ratios and sparge amounts. The only way you can be having this problem is through mistakes in measurement.

I personally feel that the kettle is the most important thing to have dead-on. I use a metal yard stick to measure my kettle volume. For me, every inch of height equates to .71 gallons of liquid. I think this is the most accurate way to measure kettle volume. The next most effective way is to precisely measure water in one gallon increments, dump them in your kettle, and make notches on your brew spoon/mash paddle/piece of wood/whatever.

Once you're confident in your volume measurements, I doubt you'll have this problem anymore. If you really are collecting 7.5gal at 1.056, then it shouldn't be hard to figure out how far to boil down.

And finally, never trust the markings on a better bottle or plastic bucket. Do the measurements yourself.

 

[Ichthy]

You need to boil the wort to your target volume. I assume you are using software to formulate recipes and predict OG? If so, the software is probably assuming you are boiling off 1-1.5 gal per hour to reach your target volume. You need to verify that your boil off is correct and adjust your boil to reach the desired volume. If your pre-boil SG is correct, your only issue is the volume of wort your getting in the fermenter.

 

[johnoswald]

Thanks for the insight. When you say "boil down" Are you saying that I should be boiling until a specific volume is reached instead of my 60 minute or 75 minute boil time? If that's the case, can you elaborate so I can get this right. Thanks again!

the amount of water boiled off is influenced by a lot of factors
the biggest thing is the amount of heat you put into the pot - the flame
minor contributors are the humidity, wind, volume in the vessel

So, boil down to a volume
But if you are addicted to following a time schedule, back add you water if you take off to much or close your eyes and let it go a little longer

But as for me, I don't worry about it

every beer I have made in the last 5 years has been drunk with great gusto
no 2 batches have been alike and I don't get up tight about variations.

 

[Frodo]

That suggests that none of this is an efficiency problem. You can effectively ignore all this crap about different water/grain ratios and sparge amounts. The only way you can be having this problem is through mistakes in measurement.

+1 What he said. Since you're on track with your pre-boil gravity all the efficiency talk is bunk. Make sure you can measure your volumes accurately.

 

[kanzimonson]

Thanks for the insight. When you say "boil down" Are you saying that I should be boiling until a specific volume is reached instead of my 60 minute or 75 minute boil time? If that's the case, can you elaborate so I can get this right. Thanks again!

You need to figure out how to simultaneously boil for 60 minutes (or whatever your recipe says) AND boil down to a target volume.

There's no way to figure it out except for trial and error. For most of us, though, it's just a light boil - some rising columns of bubbles moving around the kettle. What it's NOT is a cauldron of leaping foam.

I know what my target pre and post boil volumes are (and because I use my yard stick I also know how many inches I need to boil off), so at the halfway mark I make sure my volume is half gone. From there I can adjust the strength of the flame to arrive at the proper volume.

Using these techniques, I'm always within 3 points of my target gravity.

 

[Dave258]

I thought your first post says that you hit you 5.5 gallon ending volume... Did I miss something? Did you leave wort in the kettle?
If you hit your volumes and missed your gravity it is efficiency.
If your post boil volume was more then you needed, then yes, you need to boil down before adding your hops.

Edit:
Sorry, I just re-read your first post, and see that you hit your pre boil gravity. So yes, you had too much wort, and should have boiled off some before your first addition of hops.

 

[Yankeehillbrewer]

What efficiency are you planning your recipes for?

If for example you plan for 75% efficiency all the time and your system/process only gets you 70% you will always be chasing it. And as others have said if the volumes on your gear aren't marked well, you will have a tough time getting accurate numbers.

 

[tunoffun]

Reached target pre-boil volume of 7.50 gallons successfully!
Pre-boil gravity - 1.056 (targeted 1.053)
.
.
.
I was able to put my targeted volume in the primary...5.50 gallons.
OG was 1.063. Should have been 1.073. This seems to be a consistent thing.

There really aren't many possibilities here, assuming the information you're giving is correct and the general pattern is the same w/ all your brews.

You're apparently hitting your pre-boil gravity, which means your efficiency estimate is good. So you shouldn't be concerned with mash temps, run-off volume, or anything else along those lines. If you're getting the expected pre-boil volume at the expected pre-boil gravity (or higher), those are non-issues.

In essence, you have a sugar solution (of known concentration) you're concentrating through boiling, but you're not concentrating it as much as expected according to your calculations. That leaves few possibilities. Either your evaporation rate / boil time is different from the numbers you have plugged in, your volume measurements aren't correct, you have a volume of wort left over after transfer that you're not accounting for (deadspace), or your gravity readings aren't correct (are you accounting for temperature?).