Low efficiency

[chicknwsl]

I have recently upgraded (?) to a 48 qt coleman mash tun with braid false bottom. I have BIAB for almost a year with no issues hitting my numbers but the 2 batches I have made this weekend have had low SG pre boil but nail the numbers on the post boil. I am using 1.375 w/g lb. ratio mashing @ 152 degrees with a 168 degree sparge water I also pre warming the cooler with 180 degree water and dumping it before adding my mash water. Any suggestions? Am I doing something wrong? Also my grain mill has never been adjusted same setting for BIAB. Thanks

 

[day_trippr]

[...]the 2 batches I have made this weekend have had low SG pre boil but nail the numbers on the post boil.[...]

Assuming the measurements were done correctly the only way that works is if the pre-boil volume was excessive or the post-boil volume was low - or both.
Without knowing what really happened it's hard to know why it happened...

Cheers!

 

[chicknwsl]

So I just got the 3rd batch in the fermenter this weekend before my 21 day work stretch. All 3 pre boil numbers were way off but all 3 post boil numbers were dead on. These batches were the first ones I have ever measured the pre because I started using a brewing excel spreadsheet vs. pencil and paper. Is there any reason I should even worry about the pre boil if I'm hitting my other numbers?

Citra Blast IPA
Ridge Runner Red IPA
Chocolate Oatmeal Stout

 

[RichBenn]

By Beersmith and calibrate your system. You need to know all your losses, lke what's left in the mash tun, what your boiloff rate is, and so forth if you want to control your process and tweak it.

 

[rippajak]

How are you collecting your sample to measure pre-boil gravity? As you run wort into your boil kettle it doesn't necessarily mix homogenously. The last runnings out of your mash tun will be much lower in gravity than the first runnings, and this portion of the wort will tend to float on top of the denser first runnings. If you are pulling your sample off the top of the boil kettle you may not getting an accurate reading on the full volume in the kettle.
I also second the recommendation to pay close attention to your volume pre- and post-boil. If one or the other (or both) is off from your target that will skew your gravity readings off from your calculated ideal.
All in all, if you're hitting your numbers for final volume and post-boil gravity, then I wouldn't sweat it. You won't taste the pre-boil gravity in your finished beer.

 

[doug293cz]

How are you collecting your sample to measure pre-boil gravity? As you run wort into your boil kettle it doesn't necessarily mix homogenously. The last runnings out of your mash tun will be much lower in gravity than the first runnings, and this portion of the wort will tend to float on top of the denser first runnings. If you are pulling your sample off the top of the boil kettle you may not getting an accurate reading on the full volume in the kettle.
I also second the recommendation to pay close attention to your volume pre- and post-boil. If one or the other (or both) is off from your target that will skew your gravity readings off from your calculated ideal.
All in all, if you're hitting your numbers for final volume and post-boil gravity, then I wouldn't sweat it. You won't taste the pre-boil gravity in your finished beer.

^^^ This ^^^

Brew on

 

[Gerry_P]

Heck, I've never checked pre-boil gravity, just the gravity of whatever was in the fermenter at the end. I guess I'm lucky, since I've always ended up somewhere in the ballpark. If I actually tried the same recipe more than once for a change and wanted to duplicate a previous batch as closely as possible, I'd pay attention to it.

 

[chicknwsl]

How are you collecting your sample to measure pre-boil gravity? As you run wort into your boil kettle it doesn't necessarily mix homogenously. The last runnings out of your mash tun will be much lower in gravity than the first runnings, and this portion of the wort will tend to float on top of the denser first runnings. If you are pulling your sample off the top of the boil kettle you may not getting an accurate reading on the full volume in the kettle.
I also second the recommendation to pay close attention to your volume pre- and post-boil. If one or the other (or both) is off from your target that will skew your gravity readings off from your calculated ideal.
All in all, if you're hitting your numbers for final volume and post-boil gravity, then I wouldn't sweat it. You won't taste the pre-boil gravity in your finished beer.

I usually fill my collection vessel with a ladle from the boil kettle once transferred. I might be getting the weaker sparge wort from the top. If I whirlpool before I collect my sample I would assume that would be better.
Thanks

 

[smyrnaquince]

Let it come to a boil, then take a sample and chill it. The boil should have mixed things thoroughly.

 

[kh54s10]

I agree. If the preboil gravity was low but the amount was correct, then the post boil volume and gravity were both correct, the only possibility is the preboil reading was wrong for some reason.

Uneven mix, measurement temperature outside the range of the hydrometer...

 

[doug293cz]

I usually fill my collection vessel with a ladle from the boil kettle once transferred. I might be getting the weaker sparge wort from the top. If I whirlpool before I collect my sample I would assume that would be better.
Thanks

Just a quick whirlpool will not be enough. I know 'cause I had a low pre-boil measurement after whirlpooling with my whip. You pretty much need to run a paint mixer in the BK to get it mixed well enough. Easier to wait for a couple of minutes of boil as @smyrnaquince said.

Brew on