What is First Rest Temperature

Discussion in 'Beginners Brewing Forum' started by Brewer #230611, Jan 10, 2020.

  1. Brewer #230611

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    #1 Brewer #230611, Jan 10, 2020
    Last edited: Jan 10, 2020
    I have a robobrew and i'm trying to figure out how much water i need to boil for my mash, and the temperature etc. I've been looking at this tool: https://www.brewersfriend.com/mash/ but i'm not sure what all the terms mean.
    What is first rest temperature?

    This is the recipe that I am using: https://www.ontariobeerkegs.com/v/vspfiles/assets/images/grainkit - obk chocolate milk stout.pdf

    My friend, who also has a robobrew told me that I should plug in 0.35 for the mash water/grain ratio based on his experience.
    So i guess my question is, is the first rest temperature the temp of the water when i start adding the grains? The recipe says I need to mash at 150F/65C. Is that the value? Sorry for being such a noob.

    Also, is this the right approach for calculating the right amount of strike water? I assume that my grains will absorb 1.5 gallon of water; 1 gallon will evaporate.

    This is the calc I have:

    + 4.5 g (for mash, per the calculator)
    - 1.5 g absorbed by grains (how do you calc this?)
    -----------------------
    =3 g left in mash tun by the time sparging starts.

    If desired finished product is 5.25 gallons, i need to:

    add 2.25 g of sparge water to bring it up to 5.25 g. And then tack on another 1g for evaporation during the boil.
    So .. total water is 4.5 g mash + 3.25 g = 7.75 G
    Does that sound right?

    Thanks.
     
  2. Brewer #230611

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    I guess what i need to know is how to calculate how much sparge water I need ... based on the final amount of beer I want to end up with.
     
  3. BarbarianBrewer

    BarbarianBrewer Well-Known Member

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    I don't use an all-in-one system but the following should still apply if you do the standard mash-drain-sparge-drain method.

    The standard formula for water absorption is 1/8 gal per pound of grain. So 12 lbs of grain will absorb 1.5 gallons of water. (12 * 0.125=1.5). For the sparge I take my desired pre-boil volume and subtract the mash runoff (called First Runnings). Pre-boil volume would include evaporation from boiling. From what you indicate your pre-boil volume would be 6.25 gallons (5.25 gal in fermenter + 1 gal boil-off). So, 6.25 - 3 gal (first runnings) = 3.25 gal sparge water.
     
  4. BOB357

    BOB357 Well-Known Member

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    Probably a good idea to read the documentation for the Recipe Builder located here:
    https://docs.brewersfriend.com/recipe-builder
    As with any program, there is a learning curve and having a working knowledge of the different functions is a good place to start.
    The recipe builder, along with your inputs will calculate the volumes for you.
     
    BarbarianBrewer likes this.

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