The mash & rest schedules calculator allows you to find your target strike volume and temperature, as well as plan for up to 3 additional mash infusions.
About This Calculator
The STTP mash calculator allows you to pinpoint your specific boiling water temperature (based on your elevation) and continues to adjust this temerature accordingly through-out the remainder of your mash infusion steps based off your personal thermal loss number. If you do not know your expected thermal loss number, I encourage you to start with a value of 2-3 degrees to begin with. This number can then be dialed in by measuring your average temperature loss during the mashing process moving forward for more accurate results.
Initial Infusion Formula
r = The ratio of water to grain (quarts/pound).
Wa = The volume of boiling water added (in quarts).
Wm = The total volume of water in the mash (in quarts).
T1 = The initial temperature (°F) of the mash.
T2 = The target temperature (°F) of the mash.
Tw = The actual temperature (°F) of the infusion water.
G = Total grain weight (lbs).
Mash Infusion Formula
Adjusting for a drop in temperature
This formula is only applied when the temperature from one infusion to the next actually drops below the original temperature.
Despite it’s simplicity, this formula took me the longest time to find and translate. In it’s simplest form, the equation looks like this:
Tf = ((Va * Ta) + (Vb * Tb)) / (Va+Vb)
Va = volume of solution A whose temperature is Ta
Vb = volume of solution B whose temperature is Tb
Tf = the temperature of the solution after mixing.
In the above formula we are solving for the resulting temperature after we mix the two volumes of known temperatures together. However, since we actually know the resulting temperature (target temperature) we need to re-write the formula to find the required volume of 50F (cold water) required to reduce our temperature to our target rest temperature.
So our formula from above now becomes:
Vb = (Va * Ta) – (Tf * Va) / (Tf -Tb)
**I don’t know if I ever would have been able to figure out how to properly re-work the original formula without the help of the awesome online algebra calculator @ MathPapa.com. A huge thanks goes out to them for making such an amazing calculator.
Solve for the required number of 50F water (in quarts) needed to reduce the temperature of our example batch below.
(Ta) Starting Temperature = 118 °F
(Va) Starting Volume = 8 quarts
(Tb) Temperature of Addition = 50 °F
(Vb) Volume of Addition = ?
(Tf ) Target Temperature = 77.2 °F
Now we just need to plug the above data into our modified formula from above.
Vb = ((8 quarts * 118 °F) – ( 77.2 °F * 8 quarts)) / (77.2 °F – 50°F)
Vb = (944 – 617.6) / 27.2
Vb = 12 quarts
Adjusting For Elevation
For every 500 ft change in elevation, there is approximately a .9 degrees difference in the required temperature to boil water. In order to make the above calculator as accurate as possible, I first had to solve for what the difference every foot of elevation made.
Now just multiply your elevation (in feet) by 0.0018 to find your boiling water temperature.