Grain absorbtion

[rjb222]

This is a Granfather based question. How do I figure out my grain absorption rate to change that rate in my equipment profile? Here is what happened last brew. Strike water Calculated with the chart given in the instructions. Total grain weight 6.40 KG. Strike water 20.75 liters. Sparge water 12.90 Liters. My return was only 24 liters after sparging was complete. SG was huge expected was 1.048 actual was 1.068. I added 4 liters top up water to have a proper boil volume. I use rice hulls and a fine crush could that be making a difference in the grain absorption rate?

[Oginme]

Your grain absorption rate is your water in less your water out divided by the amount of grain.

So in the case you mentioned:

Water in = 20.75 + 12.90 = 33.65 liters

Water out = 24 liters

net loss is 33.65 - 24 = 9.65 liters

Water absorption by grain = 9.65 / 6.4 = 1.507 liters/kg.  Converted, this is about 1.44 oz of water per oz of grain (default for BeerSmith is 0.96).

Now, how confident are you in your water measurements?  Are there any other losses that need to be taken into consideration?  Your loss is about 1.5x what I would expect from a standard mash tun set up and there would be a lot of free water (wort) coming out when you remove the grain canister from the Grainfather.  Rice hulls will not absorb much water and a finer crush _could_ be a small factor, but it would not account for such a large amount of retained water.

[rjb222]

After pulling the grain-pipe There may have been a cup of wort collected I set the pipe on a bucket and add that into the boil. This is not the first brew that this has happened. On the first brew that this happened I thought I had mis-measured. I am trying to figure out why and then I can adjust my water or something else. I used the gauge on the Grainfather for the strike water and a 4 liter incrementally marked pitcher to measure the sparge water.