BIAB grain’s absorption rate question???

[Allekornbrauer]

Hello I just started using the BIAB method an I do squeeze the bag as it drain. So what would be my grain absorption rate?

 

[doug293cz]

Depends on how aggressively you squeeze, and if you use anything to increase the pressure on the bag. The only way to know the absorption rate for your process is to measure it. The calculation is:

Absorption Rate = (Strike Water Volume - Pre-Boil Volume) / Grain Weight​

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Accurate volume measurements are a must, as the calculated value can be no more accurate than the starting measurements. For highest accuracy, you should correct the volumes for thermal expansion. To correct a mash temp measurement to room temp, multiply by 0.98. Easiest way to take reasonably accurate volume measurements is to calibrate a ruler or make a stick/rod with volume markings on it. Use an accurate measuring cup to put a quart or 1/2 gallon of water in your BK, and then note the measurement on the ruler, or mark the dip-stick. More accurate than a measuring cup is to weigh out the water with an accurate scale. Water at 68°F (20°C) weighs 8.33 lb/gal.

As an initial estimate for your first BIAB brew, use 0.08 gal/lb if you think you squeeze moderately, or 0.06 gal/lb if you think you are an aggressive squeezer.

Brew on

 

[hottpeper13]

I use .06 for up to 12 lb batches and .08 for larger, gets more difficult the heaver it is.

 

[tennesseean_87]

You can always calculate your volumes to end up a little shy of target, then dilute with distilled water after the boil. I need to nail my process a bit more, but this is how I do it.