Author Topic: Grain liquor absorption in Metric values  (Read 765 times)

Offline lonte

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Grain liquor absorption in Metric values
« on: September 06, 2018, 05:47:33 PM »
This might be an old learning but its new to me. I've been using the default grain absorption figure of 0.96 since I guess day 1 but just last night, when trying to detect some inconsistencies with another brewing software product, realized that figure in BS is in fl.oz./oz

So, I did some calculations and worked out this is 0.028391L / 0.02835kg ~= 1.001 L/kg NOT 0.96. Now, BS does actually do this math internally (which explains why my 5kg 'test' beer was predicted to soak up 5.001L and not 4.8L) however if you are trying to match other brewing software that might quote grain absorption in other units (e.g. L/kg) be aware that 0.96 is not some magic constant :)

Offline brewfun

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Re: Grain liquor absorption in Metric values
« Reply #1 on: September 06, 2018, 07:53:55 PM »

if you are trying to match other brewing software that might quote grain absorption in other units (e.g. L/kg) be aware that 0.96 is not some magic constant :)

Your look into this is an excellent point that needs just a bit of context. I think it's very important to note that BeerSmith allows adjustment of absorption. Other software may not.

Absorption isn't absolute when thinking from a brewer's perspective. There is, of course, the amount of absorption that a single grit of pale barley will take up. But, there are also many other considerations.

First, the weight of a fluid ounce will be slightly less (around 3%) at mash temperature (60C) than cold (4C). The size of the grit will effect how much water it'll release.

We can then get into the amount of absorption from specialty barley and other grains. There's also the water that is inevitably trapped between grains ans mash geometry comes into play. Finally, there's the practical idea of how long do you want to wait for all free water to finish draining (it's a pretty long time).

I think the takeaway is that determining the actual absorption is important for those who need to conserve every drop. However, for most, the 0.96 is a pretty good number.

I have found the number changes depending on the brewhouse and the grain crush. I try to dial my brewery in to get maximum extraction (90+%) and tighten the water used. My absorption number is 0.7020.
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Offline GigaFemto

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Re: Grain liquor absorption in Metric values
« Reply #2 on: September 06, 2018, 10:45:51 PM »
Agreed. The only "right" number is the one that works for you. BeerSmith has a default but that doesn't mean it is the best value for everyone. Find what works for your grain, your crush, your process and put that number in to your version.

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Online Oginme

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Re: Grain liquor absorption in Metric values
« Reply #3 on: September 07, 2018, 05:34:35 AM »
Very good points all around.  Which brings up another issue which I have mentioned previously for a future improvement, moving the grain absorption from a universal setting to the individual equipment profiles. 
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