I brewed a double IPA (Hopslam clone) with a predicted OG of 1.091. Despite double-crushing my grains and mashing for 60 minutes, my pre-boil gravity was only 1.051 and my OG after the boil and chill was only 1.060. I'm not too concerned, because it will be a great beer, but I'm wondering how I missed my numbers by so much. My pre-boil volume was 7.10 gallons and I had 6.25 gallons left after a 1 hour boil. My boil-off rate was much lower than normal, because I was using a condenser to capture the steam instead of a vent hood. Acc'd to Brewer's Friend, my brewhouse efficiency was less than 50%. Usually, I'm achieving total efficiencies of 65 - 75 percent. The only change I've made is the condenser. Any idea why I missed by OG by so much?
Missed gravity numbers by a mile - help me figure out why!
- Thread starter Woodbrews
- Start date
Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:
Do you know what your mill setting was? 2 brews ago I had a lousy mash efficiency (55%) despite doublecrushing. Then I checked my setting and it had slipped to 0.045. Resetting it to 0.025 for my next brewday gave me my usual 75%.
Another thought: You got 1.060 for 6.25G. What was the predicted volume for the 1.091? Using the 1.060 x 6.25 numbers, then a 5G batch would yield 1.075. Not your 1.091, but closer.
Final thought- it's always a good idea to keep some DME on hand for those days when the numbers aren't adding up.
Final thought- it's always a good idea to keep some DME on hand for those days when the numbers aren't adding up.
chickypad
lupulin shift victim
We need more info to troubleshoot - total grainbill, mash water used, did you sparge or full volume mash?
Woodbrews
Well-Known Member
Thanks for helping me troubleshoot. Total grainbill was 14.5 lbs of grain and 2 lbs of honey. Started with 8 gallons of mash water. Did a full volume mash with no sparge. I let the bag drip, but didn't squeeze. I'll check my mill settings when I get home. I do keep DME around, but didn't think to add it!
Woodbrews
Well-Known Member
I've attempted higher gravity brews only twice, and both times I missed my targets. I think the highest I've achieved was 1.064. I didn't realize that sparging could help increase efficiency. I've introduced a new variable into my brewing by using the condenser, so I know my starting water volume will need to be reduced. I assume sparging would add to the pre-boil volume as well? So I'd need to account for that in calculating my starting volume, too.
Increased sparging efficiency is a huge driver for going with 3 vessel systems.
Your mash volume doesn't need to be any higher than a larger system; use 1-1.25 qt per lb. (less is better) Expect grain absorption of roughly 0.14 gal/lb.
The rest of the volume goes to sparging; you want to maximize you sparge water.
Cold sparging has been proven on some tests to be just as effective as hot sparging, so you can still do this with a single vessel BIAB if you choose.
To sparge hot you will need 2 vessels; at this point you might as well go with a more traditional system. Good luck.
Your mash volume doesn't need to be any higher than a larger system; use 1-1.25 qt per lb. (less is better) Expect grain absorption of roughly 0.14 gal/lb.
The rest of the volume goes to sparging; you want to maximize you sparge water.
Cold sparging has been proven on some tests to be just as effective as hot sparging, so you can still do this with a single vessel BIAB if you choose.
To sparge hot you will need 2 vessels; at this point you might as well go with a more traditional system. Good luck.
- Joined
- Dec 26, 2013
- Messages
- 4,302
- Reaction score
- 5,123
Remember too that 60 minutes for the mash is not a mandatory number.
IF you were to add a sparge step, you might spend 60 minutes with the initial mash and another 15 minutes with the sparge. You're now at 75. This is, in part, why the Aussie guys routinely mention 90 minute mash times.
It would be interesting (to me) to see what your pre-boil gravity would have been at 60 versus 90.
IF you were to add a sparge step, you might spend 60 minutes with the initial mash and another 15 minutes with the sparge. You're now at 75. This is, in part, why the Aussie guys routinely mention 90 minute mash times.
It would be interesting (to me) to see what your pre-boil gravity would have been at 60 versus 90.
Don't you have a fermenter bucket? Set the bag of grain in the bucket, pour the sparge water over it, dunk it up and down a couple times, then lift the bag of grains out. Hanging the bag to drain will get most of the wort out of it, otherwise give it a good squeeze so it doesn't drip all over.
The biggest factor in mash efficiency is the crush of the grain. If the mill is set too wide even a double crush won't do the job. A longer mash can help some but it is limited. As Soccerdad mentioned a 60 minute mash isn't mandatory. With a very fine milling I can have full conversion in less than 30 minutes with my brewhouse efficiency with a double batch sparge exceeding 80%.
- Joined
- Dec 26, 2013
- Messages
- 4,302
- Reaction score
- 5,123
Agree with the above. Love my Victoria mill for its finer crush. Most of my mashes are done in 40 minutes .. on the rare occasion when I need a dunk sparge, its still done in roughly 60. However, those are 1050 and 1060 beers, not 1090 beers. A longer mash and a sparge step might be needed for a beer that big.
Woodbrews
Well-Known Member
@RM-MN - I've read some of your posts about achieving full conversion with shorter mash times. When you say "very fine milling," what is the consistency of the crush? Is it close to flour-like? Is it possible to have too fine a crush when doing BIAB? Perhaps not, given that we typically do a full-volume mash . . . .
@soccerdad - It sounds like I need to try for a finer crush and a sparge step the next time I brew a high-gravity beer. I've had great success with beers in the 1050 to 1060 range, but I'll need to tweak my process to achieve the higher-gravity stuff.
chickypad
lupulin shift victim
Your target gravity also looks unrealistic so I would check your recipe. Your mash was 2.2 qt per gallon, if you got 100% conversion then your initial gravity without the honey would be 1.058 (no sparge). Boiled from 7.1 to 6.25 gals you'd be in the 1.065 range. The honey would add 70 pts to give about 1.076 max if my calculations are right. A quick check in beersmith with a 14.5 lb grainbill + 2 lbs honey and 75% efficiency gives 1.074 for a 6.25 gal batch.
- Joined
- Dec 26, 2013
- Messages
- 4,302
- Reaction score
- 5,123
so we gotta do math now?
My grains look like cornmeal with husk pieces mixed in. There are people doing BIAB that use a blender to make their grain even finer. I don't know if you can make it too fine but I suspect that flour would clog up the bag.
Woodbrews
Well-Known Member
I dug around in Brewer's Friend and found a version of the recipe with much more accurate numbers. For the same grain bill, it predicts an OG of 1.073, not 1.091 that was in the recipe I used. I'm not sure where the numbers in the original recipe came from, but I probably should double-check the recipes in Beersmith.
@RM-MN - "cornmeal with husk pieces mixed in" is definitely finer than my double crush. I'll experiment with a finer crush next go-round.
@soccerdad : yes, math is requried.
@Woodbrews : 14.5 lbs of malt (assuming no, or minimal, high roast malts) in 8.0 gals. should yeild a S.G. of 1.067. On your next mash measure the gravity as the mash progresses. You will see it rise and eventually start to flatten out. Let it mash until it is at or at least within a few points of the target. If it takes more that 60 to 90 minutes the crush is to coarse, the pH is out of range, or the temp is out of range. Since temp is easy to measure that is the least likely issue. A gravity of 1.067 in the 7 gals you collected plus the 2 lbs of honey added to the boil should yield an O.G. of 1.090 in 6 gals. of finshed wort.
@Woodbrews : 14.5 lbs of malt (assuming no, or minimal, high roast malts) in 8.0 gals. should yeild a S.G. of 1.067. On your next mash measure the gravity as the mash progresses. You will see it rise and eventually start to flatten out. Let it mash until it is at or at least within a few points of the target. If it takes more that 60 to 90 minutes the crush is to coarse, the pH is out of range, or the temp is out of range. Since temp is easy to measure that is the least likely issue. A gravity of 1.067 in the 7 gals you collected plus the 2 lbs of honey added to the boil should yield an O.G. of 1.090 in 6 gals. of finshed wort.
Were you working from a printed recipe? I always enter any recipe I'm going to brew into Brewer's Friend (where I manage my recipes). This serves several purposes. First, many recipes assume much better efficiency that I typically get. I've seen recipes with kits that seem to assume 85% efficiency...probably to justify including less grain. When I put it into brewer's friend, I can set to my efficiency and adjust the ingredients if necessary.
I also keep my inventory in Brewer's Friend so I can easily generate a shopping list of ingredients and, when I brew, decrement my inventory.
It's a great sanity check, plus you have it in an easy to access place in case you want to brew it again in the future. I'm in the habit of taking any recipe I think looks like it's worth brewing and entering it in for future reference.
Woodbrews
Well-Known Member
Thanks for the tip. I discovered Brewer's Friend a while back, but have still been brewing a lot from pre-made kits. I never thought to check the assumed efficiency of a recipe kit. That said, I've brewed a couple of duds from recipes on Brewer's Friend. I think it's time to learn more about the ingredients and start making my own recipes!
I would say squeeze the heck out of the bag in the future. I've had my pre-boil SG go up 6 or 7 points after a good squeeze. And double crush your grains too. I've seen people recommending as small as 0.2-0.25. Good luck in the future!
I built this, and pour my sparge water on top of the bag and squeeze with industrial latex gloves....
Exactly. You dont have to deal with the usual "stuck sparge" because its BIAB, so crush it like crazy.. and the squeeze myth has been debunked several times over... go ahead and squeeze the bejesus out of that thing.
I also ran your numbers, and my results are very similar to @chickypad 's. I used 34 pts/lb for honey, so 68 pts for 2 lbs. Your grain absorption rate came in at 0.062 gal/lb, which seems low for an unsqueezed bag (I squeeze a lot to get that kind of grain absorption.) If you had gotten 100% conversion efficiency, that grain absorption gives you an 80% lauter efficiency, a pre-boil gravity of 1.058, a post boil gravity w/o honey of 1.066, and after honey 1.077. Your OG of 1.060 puts your actual conversion efficiency at about 72% - 73%, which is pretty low. Your mash efficiency was about 60%.
So, the crush finer advice of previous posters is spot on in order to improve your conversion efficiency.
Brew on
So, the crush finer advice of previous posters is spot on in order to improve your conversion efficiency.
Brew on
homebrewer_99
Well-Known Member
- Joined
- Feb 1, 2005
- Messages
- 19,581
- Reaction score
- 1,218
- Location
- I-80, Exit 27 (near the Quad Cities)
So, how many gravity points are there in a mile?
That depends on whether it is an African or European swallow.
homebrewer_99
Well-Known Member
- Joined
- Feb 1, 2005
- Messages
- 19,581
- Reaction score
- 1,218
- Location
- I-80, Exit 27 (near the Quad Cities)
newnick
Well-Known Member
If this is a 5gal batch and you have 6.25 gals left that might be why your gravity is so low. You need to boil off more water.
