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How much grain before I overflow the kettle?

Brewitall

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I just received a 18 gal Brew In Bag (BIAB) Kettle from Stout.  As an aside, solid, but could use a sight glass and thermowell port.

Stout's website says the basket will hold 29 pounds of grain.
Information I can find indicates 1.6 fl oz per oz of grain.  http://www.aqua-calc.com/calculate/weight-to-volume

I design a 10 gal batch with 29 lbs of grain, which near as I can figure is 5.7 gallons.

BS says 15.8 gallons of water converting everything to fl oz gives a total volume:
2022.4 fl oz Water
742.4 fl oz Grain
2765 fl oz total=21.6 gallons

Which is right in line with adding volumes using gallons (21.5 Gallons). 
Assuming an absorption of 0.586 fl oz/oz (BIAB Grain Absorb), for 742.4 fl oz of grain, that should (I'm guessing here) reduce the volume by 272 fl oz, or 2.12 gallons which is 19.38 gallons, still greater than the 18 I have to work with.

Other than trial and error, how can I figure out how much grain and water I can put in the pot for the mash?  I guess I don't understand the grain volume and BIAB Grain Absorb calculations.

Also if anyone could describe how they add grain to their BIAB system after getting the water up to temperature and their experience on how much volume grain and water displace that would be very helpful.
 

jtoots

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Beersmith will tell you the volume, and will give you a red light if it's over the volume of your kettle or mash tun... at least that's how it looks for me when doing standard all-grain.  BIAB I'm not sure.  I think it should be on the mash tab, but I'm not in front of my software. 

By the way what are you brewing?  That's a high octane brew at 29 lbs for 10 gallons!  I leave the grain absorption number alone and tweak the mash thickness number if I'm doing a batch where I'm near the limit of my mash tun.
 

Brewitall

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Found it!  I wasn't exposing the "Mash Volume Needed" field on the design page.  Turns out max capacity is calculated as 24 lbs grain and 16.44 gal water.  I have been brewing an IPA in my old equipment keggle-11 gallon cooler/mash tun-7 gallon conical that uses 18lbs of grain single infusion light body to output 6 gallons to the fermentor at between 18-20 Plato.

I'm eyeing the SS Brewing 14 gallon Chronical, and was trying to scale the recipe up to 11 gallons into the fermentor.  Looks like I can hit a max of 16.5 Plato with the grain/water ratio and would need 3 lbs of DME. 

I'm going to do a 6 gal batch next weekend and try to get some good measurements so I can more accurately estimate max system capacity and efficiency. 
 
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