Water Absorption by Grain according to Beersmith.

I use a combination of  beersmith and manual calculations for my brew day, and recently I noticed that there was a difference in the rate of water absorption by grain between my own calculations and beersmith.  I was using a value of 0.2 g/lb and beersmith was using 0.12 g/lb.  Previously there wasn’t a way to adjust this value, but it has been added in version 2.  See Here.  You can access the setting under Tools|Options|Advanced Options: Grain Absorption.

The problem is, the adjustable value is in units of fluid ounces of water to ounces of grain, and this value is usually stated in gallons to pounds.  The following is how the math works for converting these units:

Beersmith Value: 0.96 fl oz of water / 1 oz grains

• 1 US fluid ounce =  0.0075 US gallons
• 1 ounce = 0.0625 pounds
• 0.0078125 gallons of water / 0.0625 pounds = 0.12

0.12 gallons of water / lbs of grain is the rate that Beersmith is using.  I want to adjust mine to 0.2 gallons / lbs.

solve for x:

• x gallons of water / 0.0625 pounds = 0.2 gallons/lbs
• x = 0.2 gallons/lbs * 0.0625 lbs
• x = 0.0125 gallons

now convert:

• 1 US fluid ounce =  0.0075 US gallons
• x fluid ounces = 0.0125 gallons
• x = 0.0125 / 0.0075
• x = 1.67
• 0.0125 gallons of water = 1.67 fluid ounces

So the new beersmith value would be Beersmith Value: 1.66 fl oz of water / 1 oz grains.

Hope that makes sense.