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Help hitting my OG with Brew In a Bag.

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When I use BIAB I get different grain absorption rates with different grain bills. For instance wheat doesn't absorb much at all. In order to try and have consistency with my process, I decided to not guess my absorption rate and just stick with 4.5 gallons  pre mash every time.

I told this to my LHBS (great guy) and he said instead I should try to focus on getting the same amount volume of pre boil and post boil liquid. He says this would be a better thing to tighten up my process. But seeing as I am having a hard time doing that, I don't know what I should do.

Can I get some thoughts and advice on this? By the way I usually get around 80% efficiency.

klickitat jim:
I'm on the low end of procedures that call for permission. However I'm getting much better over time at close to equal runnings and pre and post boil volumes. I have a big ss stir spoon that is marked at six gallons and seven gallons. Harder to explain than it is to do, but basically I ballpark my absorption at a gallon per ten pounds. I add that extra absorption water to my mash then brew away. I start one hour boils with six gallons and adjust from there for more boil time or more than normal hops. My IPA starts with seven gallons. I usually hit 5 gallons at the end, or pretty close.

Do you squeeze your bag? That should help even out the differences between different grain bills. I honestly don't factor in a difference in absorption at all regardless of my grain bill. I probably get a bigger variation in my boiloff rate than my absorption. But I'm pretty laid back about the my brews. If I miss my OG by 2-3 points it's no big deal.

I've consistently found that absorption is .12gallons/lb regardless of the type of grain in the grist.

Is your 80% efficiency mash/Lauter or brew house.? They mean different things and by pinpointing which is which you can narrow down where your process is messing you up

Thanks for the replies guys. Yes I do squeeze the bag. And my efficiency is mash not brew house. I have measured my grain absorption to be 0.07 gallons/lb of grain, however sometimes its .10 and sometimes its .03 (with the wheat).

I guess if i dont have as much grain absorption I can add water to my preboil so i can focus on keeping the volumes of pre/post boil the same, but will that mess with my OG anyways lol?


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