Missed SG by 20 points

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jerryalan

jerryalan

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I brewed what was supposed to be an Imperial IPA today. Using Beer Smith with the brewhouse efficiency set at 75% my recipe calculated to have a 1.082 SG. However, I ended up with 1.062 instead. Here are my grains:

5.5 gallon batch

14 lbs Rahr 2-Row Pale
2 lbs Crystal 20L
3.2 oz Chocolate 350

I mashed (1.25 qt per pound) at 148 for 60 minutes, then batch sparged for 10 minutes. Mash temps were maintained using RIMS

I boiled for 90 minutes with 1.2 oz hop additions at 90, 60, 30, 15, and flame-out.

The two things that stand out for me is that at the end of the boil I had to add about a half gallon of water to make up for the loss after squeezing as much wort out of the hop bag as I could. Also, this was my first time using the RIMS so I auto-tuned it with the grains in the MLT but didn't start the mash timer until it was finished tuning. About 15 minutes into the mash I found that it was reading about five degrees lower than the actual temp so I changed the pd value and it was fine after that.

Any ideas?
 
20 points is huge. I don't think 1/2 gallon of water will swing it that much. I know my efficiency goes down somewhat as the lbs of grain increase, but not that much. Sounds like for some reason your efficiency was not what you were expecting it to be. Did you check your pre-boil gravity? what was it?
 
AKbrewer said:
Did you check your pre-boil gravity? what was it?
Click to expand...

I know that would probably answer my question but I didn't check it. I was going to brew an APA for my next batch but I think I'm going to do this one again and take better notes.
 
jerryalan said:
I brewed what was supposed to be an Imperial IPA today. Using Beer Smith with the brewhouse efficiency set at 75% my recipe calculated to have a 1.082 SG. However, I ended up with 1.062 instead. Here are my grains:

5.5 gallon batch

14 lbs Rahr 2-Row Pale
2 lbs Crystal 20L
3.2 oz Chocolate 350

I mashed (1.25 qt per pound) at 148 for 60 minutes, then batch sparged for 10 minutes. Mash temps were maintained using RIMS

I boiled for 90 minutes with 1.2 oz hop additions at 90, 60, 30, 15, and flame-out.

The two things that stand out for me is that at the end of the boil I had to add about a half gallon of water to make up for the loss after squeezing as much wort out of the hop bag as I could. Also, this was my first time using the RIMS so I auto-tuned it with the grains in the MLT but didn't start the mash timer until it was finished tuning. About 15 minutes into the mash I found that it was reading about five degrees lower than the actual temp so I changed the pd value and it was fine after that.

Any ideas?
Click to expand...

Beersmith says that adding .5gal water to a 1.082 SG wort of 4.5 gallon will drop it to about 1.074. Thats a start. You can loose 10 points pretty easily by running your wort off too fast. Have you used your false bottom before? Are you using a different base malt? As long as conversion is complete then its an issue with your runoff or sparge methods.
I've always had nearly 100% complete conversion when the wort is crystal clear. I've had better brewhouse eff. when i start the run off and just add hot water to the top of the grain bed. I usually get around 75-78%. I've learned (the hard way) to check you preboil gravity to see where you stand. That way you can make any adjustments you need without being screwed at the end of the boil.
Cheers
 
I just noticed that I have my recipe set for a 60 minute boil. That's probably why I lost a half gallon more of wort than expected.
 
Yooper said:
But all recipes are for 60-90 minute boils. How much do you usually boil off over what time period?
Click to expand...

This is just my third all-grain batch so this probably isn't 100% accurate yet buy I'm usually boiling off about a gallon per 60 minutes. I'm still tinkering with my burner adjustments to hit that mark.
 
Yep, that's probably the reason for an "extra" loss of 1/2 gallon, then!

How was your crush? Did the grain look completely crushed, with few intact hulls? That's usually the reason for poor efficiency.

I get poorer efficiency on "bigger" beers, by the way- many of us do. It's because you have more grain, but you don't use as much water to sparge (comparatively) since you generally stop when you reach your boil volume. If you sparge with .5 gallons per pound of grain, you'd probably have much better efficiency, but you'd have to boil for 5 hours to get down to 5 gallons! Many of us just plan on a lower efficiency for larger grain bills. In my cause, I might get 65-68% with your grain bill on my system.
 
Yooper said:
How was your crush? Did the grain look completely crushed, with few intact hulls? That's usually the reason for poor efficiency.
Click to expand...

The grains were brutalized but there were a lot in intact hulls. The mash wort was running very clear throughout the RIMS after a few minutes too.
 
Thanks for everyone's replies. I'm going to brew this batch again in the next four weeks and use enough sparge water to get a gallon more per hour of boil. I'll also check my pre-boil gravity.

Yooper, do you think it'd be beneficial if I did a thicker mash, maybe 1 quart per pound, and increased the sparge water to make up the difference? Perhaps I should keep some DME on hand to get the SG where I want it to be when doing big beers.
 
Good that you figured out your problem, but I just want to reiterate:

1) You MUST take a preboil gravity reading. Don't go through an entire brew just to find out you're off by 20 points when the wort's already in the fermenter.
2) Do not ever top off. I used to do this because like a lot of homebrewers I was greedy for my 5 gallons. If you're determined to have 5gal of product, you have to brew 6gal batches.

If you combine these two points, you'll be able to hit your target OG within 2 points every time. Just measure the gravity and volume at the beginning of the boil, do some quick math, and then you'll know what postboil volume you'll need to hit your gravity. THEN (and this is a point that most people don't think of), make sure your IBUs will be right for your planned volume.
 
jerryalan said:
Thanks for everyone's replies. I'm going to brew this batch again in the next four weeks and use enough sparge water to get a gallon more per hour of boil. I'll also check my pre-boil gravity.

Yooper, do you think it'd be beneficial if I did a thicker mash, maybe 1 quart per pound, and increased the sparge water to make up the difference? Perhaps I should keep some DME on hand to get the SG where I want it to be when doing big beers.
Click to expand...

No, I'm not a fan of thick mashes because of some possible pH issues.

I'd keep some DME on hand, though- when I first started AG brewing, I had several brews that had low preboil OGs and some DME was a life saver!
 
Before I even start my mash I figure out how much wort I want in my fermenter. From there I do 1.33 qt per pound to get my strike water. Depending on my grain bill, I add water to that number to account for absorption. Then I subtract that number from my total wort number. That's my sparge water, so I divide by two and that's my two sparge numbers. Then I add one gallon to each sparge number for avaporation and go to town. Hit my gravity every time. But the pre boil gravity is important and having DME on hand wll allow you to correct gravity misses. The only numbers I'm. Anal about is temps. Hope my method helps. Ill probably get tore apart for it, but I've been making some very good beers with my method
 
As well as all the advice above I would also suggest you set your efficiency lower in your brewing software for a more reasonable calculation of your predicted gravity. I batch sparge and my efficiency has been, and will likely remain (as in I am not interested in messing with my process anymore,) to be 65%.

FWIW

Steve da sleeve
 
I'm catching up on my BYO reading and have been noticing in many Style Profile article recipes that when you mash at low temperatures to achieve a higher fermentable wort you should raise the mash temp and do a rest at 156-158. I did not do this. I simply mashed for an hour at 148 and batch sparged with 170 water. Could that have contributed to my lower OG? I also didn't check for conversion completeness because I didn't have anything to test it with but have since then purchased some iodophor. I'm wondering if I also needed to mash longer.

My next batch was going to be my APA but that's being bumped so I can try this IIPA again with better notes and technique.
 
jerryalan said:
I'm catching up on my BYO reading and have been noticing in many Style Profile article recipes that when you mash at low temperatures to achieve a higher fermentable wort you should raise the mash temp and do a rest at 156-158. I did not do this. I simply mashed for an hour at 148 and batch sparged with 170 water. Could that have contributed to my lower OG? I also didn't check for conversion completeness because I didn't have anything to test it with but have since then purchased some iodophor. I'm wondering if I also needed to mash longer.

My next batch was going to be my APA but that's being bumped so I can try this IIPA again with better notes and technique.
Click to expand...

Sometimes cooler mashes (under 150) need 90 minutes to fully convert, so checking for conversion should really help. I don't see the need to boost the temperature up to 156 at the end, once the mash is converted, especially if you're going to do a mash out or a batch sparge with water hot enough to get the grain bed to 168.
 
Yooper said:
Sometimes cooler mashes (under 150) need 90 minutes to fully convert, so checking for conversion should really help. I don't see the need to boost the temperature up to 156 at the end, once the mash is converted, especially if you're going to do a mash out or a batch sparge with water hot enough to get the grain bed to 168.
Click to expand...

Thanks again! If I run into more problems next time I brew this I promise I'll have a more complete brew session with plenty of notes to share :)
 

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