BIAB newbie with low OG

[MusicLife]

So i have done 2 BIAB batches this past week ( my first 2 ever) and both batches i came in under OG. The way i did it was add all the water from the mash and sparge to start and mashed for 90mins. Then after boil i had the required amount of wort but gravity was over 6 points off both times. 1st batch was an irish red calling for 1.054 and i got just around 1.046 and the 2nd was a brown ale that was closer but still off.

I cant seem to pin down a step i did incorrectly but if anyone has some advice that would be very much appreciated.

1st batch was around 7.8 gallons in the mash and 2nd was 8.66. i mashed both around 155 as called for.

 

[McKnuckle]

A relatively fine grind helps maximize BIAB efficiency. If you had the grains milled at a homebrew shop, they are notorious for milling in a "middle of the road" sort of way. That could be one factor.

The next factor is simply the method by which you are predicting those OG values. How much grain was mashed with 7.8 / 8.66 gallons in the two examples, and what mash efficiency percentage did you predict?

The mash temp and duration you used are both fine. If you got the expected post-boil volumes, that's great! Don't screw around with the volume part of your calculations, then.

 

[MusicLife]

A relatively fine grind helps maximize BIAB efficiency. If you had the grains milled at a homebrew shop, they are notorious for milling in a "middle of the road" sort of way. That could be one factor.

The next factor is simply the method by which you are predicting those OG values. How much grain was mashed with 7.8 / 8.66 gallons in the two examples?

The mash temp and duration you used are both fine. If you got the expected post-boil volumes, that's great! Don't screw around with the volume part of your calculations, then.

The place i got it from ran it threw twice due to the fact i was using BIAB, not sure if that is adequate? I dont have a mill of my own but can get one for 50 bucks if it would help out more.

The brown ale was as listed below. It called for 3.46 strike water and 5.20 sparge, so i combined them and mashed. I did have a little over 5 gallons after but hardly any and it was heavy with sediment so wasnt to upset with leaving it. This one called for 1.049 OG and i was a lot closer with this one but still under.

8.5 lb maris otter
4 oz chateaux biscuit malt
.5 lb weyermann cara amber malt

 

[McKnuckle]

Well, you may not wish to count the volume of wort that contained sediment, but unfortunately the recipe does. That extra volume means you either boiled off less wort than expected, or you simply started with too much water, which I think is the case here.

You've listed 9.25 lbs of malt. You don't say if you drip-drained the bag or squeezed it, but let's predict an average absorption rate of 0.1 gal/lb. So you will lose 0.925 gal going into the boil. You'd thus have 7.74 gallons of collected wort to boil.

What is your boil-off rate and how long did you boil? To reach anywhere close to 5 gallons post-boil, you are evaporating far more than typical (2.75 gallons). So I will bet that's not actually happening, and you're ending with more than 5 gallons. Even a half gallon extra is 10% more; it makes a difference.

It's not your process steps that are off - it's the liquid volumes used. You can't trust a recipe to give you water volumes other than a basic batch size target. You need to refine these volumes so they match your system's performance.

 

[MusicLife]

Well, you may not wish to count the volume of wort that contained sediment, but unfortunately the recipe does. That extra volume means you either boiled off less wort than expected, or you simply started with too much water, which I think is the case here.

You've listed 9.25 lbs of malt. You don't say if you drip-drained the bag or squeezed it, but let's predict an average absorption rate of 0.1 gal/lb. So you will lose 0.925 gal going into the boil. You'd thus have 7.74 gallons of collected wort to boil.

What is your boil-off rate and how long did you boil? To reach anywhere close to 5 gallons post-boil, you are evaporating far more than typical (2.75 gallons). So I will bet that's not actually happening, and you're ending with more than 5 gallons. Even a half gallon extra is 10% more; it makes a difference.

It's not your process steps that are off - it's the liquid volumes used. You can't trust a recipe to give you water volumes other than a basic batch size target. You need to refine these volumes so they match your system's performance.

I squeezed a bit but then let it drip until it was only a VERY slow drip and added the drippings into the kettle until boil. 7.74 seemed pretty close to what i had pre boil. I did boil a little longer than 60mins in order to get the volume down some but as you said there was still a little over 5 gallons. My carboy has about 5.25 in it atm but there is a solid inch or so of crud at the bottom.

I use a keg as a kettle. It sounds like the 1st step to correction is figuring out the boil-off rate to maybe lessen the amount of water to start with?
I appreciate to assistance!

 

[McKnuckle]

A typical boil-off rate with a keggle (I assume that's what you mean by keg?) is 1 to 1.5 gallons per hour.

Check out the spreadsheet on this BIAB Tools page to see how the volume variables interact. Check out some other software, like the recipe builder on BrewersFriend.com, to see how to predict OG based on starting grain weights and water volumes.

 

[MusicLife]

A typical boil-off rate with a keggle (I assume that's what you mean by keg?) is 1 to 1.5 gallons per hour.

Check out the spreadsheet on this BIAB Tools page to see how the volume variables interact. Check out some other software, like the recipe builder on BrewersFriend.com, to see how to predict OG based on starting grain weights and water volumes.

Yes sorry it is a keggle. Based on the predicted boil off rate you listed I definitely had to much to start (about half to full gallon to much). Also the recipe i have stated to bring strike temp to 170 then add grain, but everything else ive seen/read only says 160, does that affect anything?