A Brew in a Bag (BIAB) Tutorial

Step by step instructions on how to brew beer using the brew in a bag mashing method and this BIAB Calculator

  1. Create your beer recipe or find a recipe from a website like Brewer's Friend
  2. Plug recipe values into tool the biabcalculator.com BIAB calculator. You should know the following :
    • Grain Bill- Total weight of the grains in your recipe. Do not include weights for sugars and other non-grain adjuncts in this value.
    • Grain Temperature - Take the temperature of your dry grain on brew day to aid in hitting your intended mash temperature.
    • Batch Size - Total beer you intend to put into the fermenter.
    • Mash Temperature - The temperature you intend to target for your infusion mash (153 F / 67 C by default)
    • Boil Time - Total time to boil the wort based on your recipe
  3. If you know your system parameters add those to fine-tune your results, otherwise leave the defaults in the BIAB Calculator.
    • Kettle Size - The total volume of your boil kettle
    • Trub - Amount of hops, boil material and wort you leave in your kettle after you transfer to your fermenter
    • Boiloff Rate - Volume of wort per hour you lose to evaporation in your system. To get the best results you should take measurements to find this for your particular brewing system and boil strength.
    • Grain Absorption - Volume of wort the grain retains after the mash. The BIAB Calculator default value for Grain Absorption assumes you let your grain bag drain naturally by gravity alone and do not squeeze the grain bag (see next step.) To get the best results this is another value you will want to take time to measure for your brewing system as variants in mill gap can affect this number.
  4. About Squeezing the Grain Bag - Some brewers choose to squeeze the grain bag after all the wort drains by gravity to get more wort. If you do this you will need to set absorption value a bit lower than the default value set in BIAB Calculator since the grain will end up not retaining as much liquid.
    • The Grain Absorption value in BIAB Calculator defaults to 0.045 Gal/Pound (0.3755 kg/L) and assumes you do not squeeze the grain bag after it is left to drain by gravity.
    • If you DO squeeze the grain bag, change the Grain Absorption value to around 0.031 Gal/Pound (0.28 L/kg)
  5. Start heating your mash water up to the Strike Temperature value indicated in the Output section of the BIAB Calculator.
  6. Crush your grains now if they are not pre-crushed. With Brew in a Bag mashing you can crush more than you might normally to get a bit more mash efficiency.
  7. When the brewing water is up to your planned strike temperature add grain to bag and stir well. BIAB Calculator will give you a warning in the Output section next to the Total Mash Volume value if the total volume of mash water and grain will cause your kettle to overflow.
  8. Let the mash sit for the conversion time in your recipe. Default is 60 minutes.
  9. If you want to do a mash out to icrease your extraction efficiency and get a stronger potential alcohol you can heat the wort up to 165F / 74C and hold it for 10 minutes to mash out. Unlike mashing with a false bottom or screen, the mash out step in Brew in a Bag style mashing does serve to help extract more sugars out of the grains. Make sure you do not burn the grain bag on the bottom of the kettle while heating. Some brew in a bag brewers use a colander or metal cake rack as a spacer between the bottom of the kettle and the grain bag to ensure the bag does not burn.
  10. Remove the grain bag and let it drain by gravity either over your kettle or on a bucket. BIAB Calculator's default Grain Absorption value assumes this gravity drain step. Adjust the Grain Absorption value if you deviate from this.
  11. If you factored-in a step to squeeze the grain bag, do this once the wort has stopped draining from the grain bag on its own.
  12. Follow your recipe for boil for boil time, hops, and adjunct additions.
  13. Chill your wort and transfer to fermenter leaving the wort and trub (hops, break material) amount you specified in the Trub value in the BIAB Calculator. Measuring the amount of trub you typically leave behind in your kettle and using this value in the calculator is another way to ensure get the best, most predictable results for your brewing system.