BIAB low volume

[JamieGalea]

Hi

I did my first BIAB. My recipe was 3kg Wheat / 1.5kg pilsner. I did a full volume mash. 27 ltrs volume for mash. After 60min I removed bag and checked gravity. It was low 1.023 with a volume of 22ltrs.
I went on to boil for 60mins added hops is 40g in total. I did not crush my grain finely but left it a bit coarse.

I did not take reading of end of boil but when I chilled and transferred to my fermenter I ended up with only 15 ltrs of wort but with a gravity of 1.042 which is ok for a wheat beer.

How can I increase my final volume?
Was it that I had a bad efficiency?

 

[RM-MN]

How can I increase my final volume?

3 choices.
1. Start with more water.
2. Sparge to get more volume.
3. Reduce the heat when you boil so you don't boil off as much.

Was it that I had a bad efficiency?

Almost certain. The biggest factor that drives mash efficiency it the milling of the grain. Wheat is worse than barley because the grains are smaller and harder to crush. If the wheat doesn't get crushed, it yields little sugars to the wort.

 

[Sammy86]

How can I increase my final volume?
Was it that I had a bad efficiency?

Did you squeeze the bag? If not, you left a bunch of sweet wort behind that probably would have given you more volume and increased your gravity.

Using BIAB you can afford to crush finer because you have the bag...some dust isn't going to hurt you because you have the bag to filter it.

Like @RM-MN said...use more water or sparge and you'll increase your volume as well.

 

[JamieGalea]

From the research done and your replies, i would say increase water if im keeping the same heat to boil and most of all the grain mill, it definetly needs to be finer.

 

[DBhomebrew]

After 60min I removed bag and checked gravity. It was low 1.023 with a volume of 22ltrs.

when I chilled and transferred to my fermenter I ended up with only 15 ltrs of wort but with a gravity of 1.042

These numbers are suspect. Gravity points (1.0xx) times volume at the top of the boil should equal the same at the end of boil.

22*23=506
15*42=630

You're looking at 3 separate things.

1. Improve measuring accuracy.
2. Improve conversion efficiency. (Grind finer, mash longer)
3. Improve and/or account for lauter efficiency. (Use more water, sparge, etc)

 

[doug293cz]

At 4.5 kg of grain and 27 L of strike water, your pre-boil SG should have been about 1.045 - 1.046, if you had gotten 100% conversion efficiency. If your pre-boil SG reading of 1.023 is correct, then that works out to a conversion efficiency of only 48 - 49% (which sucks.)

What was the wort temperature when you took your pre-boil SG, and did you correct the reading for actual temperature? If you took your reading at mash temp (~65°C) and didn't correct, then your corrected pre-boil SG would have been about 1.039 - 1.041(used this calculator.) If your correct pre-boil SG was 1.040, that would put your conversion efficiency at about 86 - 87%. Much better than above, but still not great. Good conversion efficiency is 95 - 100%

However, a 1.040 pre-boil SG, pre-boil volume of 21.6 L and post-boil of 15 L would give an SG of 1.057 - 1.058, which is higher than you got. Ignoring your pre-boil SG measurement, and assuming your volume measurements and post-boil SG are accurate, results in a "true" pre-boil SG of 1.029, and a conversion efficiency of ~62%.

With a measured pre-boil volume of 22 L, correcting volume to room temp results in a pre-boil volume of 21.6 L. This puts your grain absorption rate at 1.2 L/kg. A reasonably well drained BIAB bag should give a grain absorption rate of less than 0.9 L/kg. Either your bag draining was very inadequate, or your strike water and/or pre-boil volume measurements were inaccurate.

Since your conversion efficiency was quite low, you need to crush finer and/or mash longer to improve it (as noted by @DBhomebrew .)

Since your grain absorption rate was apparently very high, you need to drain your bag better (= longer.) This will increase your pre-boil volume without having to increase your strike water volume.

Your boil off was 6.6 L, which is too high. Boil off for your batch size should be less than 5 L, and preferably less than 4 L. Turn the heat down during boil - you don't need a maelstrom in your BK. This will increase your final volume to your fermenter.

Finally, there is reason to question the accuracy of you volume measurements, since your measurement values are not self consistent. Work on improving the accuracy of your volume measurements (again as @DBhomebrew mentioned.)

Brew on

 

[JamieGalea]

Valid points which would help me out next time.

I measured the preboil gravity at mash temp which was 65C. I do not understand the term "correct reading for acutal temp" what do you mean please ? @doug293cz

 

[balrog]

He means there is expansion due to heat. Water volume at 68F expands about 2.5% when heated to 150F. Water at 68F expands about 4% when heated to boiling, 212F.

Measuring volumes was one of the difficult things for me to nail down due to my garage floor, propane burner geometer and kettle -- it can be uneven, not level. That makes taking a reading from marks inside the kettle suspect.

 

[jtgoral]

For 5.5 gallon final batch I start with 8.25 gallons of water when doing my BIAB. I boil ales and lagers for 60 minutes. Convert this to metric to your liking.

 

[marc1]

Valid points which would help me out next time.

I measured the preboil gravity at mash temp which was 65C. I do not understand the term "correct reading for acutal temp" what do you mean please ? @doug293cz

Hydrometers are calibrated at a specific temperature, mine is 60F. If you measure at a different temperature, you have to correct for it. Being that far off from the calibration temp may lead to suspect results anyway, though, even with a correction calculator.

 

[doug293cz]

He means there is expansion due to heat. Water volume at 68F expands about 2.5% when heated to 150F. Water at 68F expands about 4% when heated to boiling, 212F.

Measuring volumes was one of the difficult things for me to nail down due to my garage floor, propane burner geometer and kettle -- it can be uneven, not level. That makes taking a reading from marks inside the kettle suspect.

Correct, water expands when it is heated. Expansion from 68°F (20°C) to 150°F (65.6°C) is actually 1.8%, and from 68°F (20°C) to 212°F (100°C) is 4%. For the most accurate calculations involving volumes (e.g. efficiency), all measured volumes should be corrected back to 68°F (20°C.)

Tilt of vessels can affect volume readings taken from markings on the side of the vessel, and vessel markings are often inaccurate anyway.

You can use a ruler to measure the depth of the liquid and convert that to a volume. To determine the depth to volume correlation, add a gallon, or a few liters, at a time to the vessel, and measure the depth. Repeat this several times until you have as much volume in the vessel as you will ever have when brewing. Then graph (or curve fit in a spreadsheet) the depth vs. volume. This works even for non-cylindrical vessels. You can also just make volume markings on a rod/stick (a dipstick) at various known volumes.

If you take depth measurements in the center of the vessel, and hold the measuring device vertical, then vessel tilt will not affect the volume measurement.

Hydrometers are calibrated at a specific temperature, mine is 60F. If you measure at a different temperature, you have to correct for it. Being that far off from the calibration temp may lead to suspect results anyway, though, even with a correction calculator.

Typical hydrometers are calibrated at either 60°F (15.6°C) or 68°F (20°C.) The calibration temp of your hydrometer should be printed on the scale card inside the hydrometer stem.

Since water expands with increasing temperature, the density decreases. Hydrometers actually measure density, so the readings go down with increasing liquid temperature. There are calculators that will correct the readings. You can find one here.

Brew on

 

[TkmLinus]

I ran into the same problem with poor efficiency. IslandLizard suggested I set my mill to .025". My efficiency shot way up after tightening the gap. Good luck!