The Home Brew Recipe Calculating Program - Mash Temperature Calculator

This is the Mash Temperature Calculator. By entering values for the fields on the screen, this calculator can determine: the required amount of initial water at the entered temperature necessary to hit a mash temp, the required temperature of the initial water at the entered volume necessary to hit a mash temp, the required amount of water to add (infusion) at the entered temperature necessary to boost the mash from one temp to another, the required temperature of the water added at the entered volume necessary to boost the mash from one temp to another, and (finally) the required amount of mash that must be removed, heated to the entered temperature, and then added back to the mash (decoction) to boost it from one temp to another.

Fields

Malt Weight - This field indicates the amount of malt used. Changing this field will cause the Infusion Volume and Decoction Weight to be recalculated.
Weight Units - This field is used to indiciate the weight units used by the calculator. Click on the button in the corner of the field to change the units and convert the Malt Weight and Decoction Weight fields to the new units.
Malt Heat Capacity - This field is used to indiciate the heat capacity of the crushed malt. Typically this number is about .4 and varies depending on the moisture content of the malt. The following table shows the malt heat capacity (MHC) as a function of its moisture content.
```
	% moisture      MHC in Btu/lb/degF
	  0                     0.38
	  2                     0.39
	  4                     0.40
	  6                     0.41
```
Changing this field will cause the Infusion Volume and Decoction Weight to be recalculated.
Water Volume - This field is used to indiciate the amount of water that has already been added to the mash. Changing this field will cause the Infusion Volume and Decoction Weight to be recalculated.
Volume Units - This field is used to indiciate the volume units used by the calculator. Click on the button in the corner of the field to change the units and convert the Water Volume and Infusion Volume to the new units.
Current Temp - This field is used to indiciate what the current temperature of the mash is. Changing this field will cause the Infusion Volume and Decoction Weight to be recalculated.
Temperature Units - This field is used to indiciate the temperature units used by the calculator. Click on the button in the corner of the field to change the units and convert the Current Temp, Added Temp, and Final Temp to the new units.
Final Temp - This field is used to indiciate what the current temperature of the mash is. Changing this field will cause the Infusion Volume and Decoction Weight to be recalculated.
Added Temp - This field is used to indiciate what the temperature of the additional water or decocted mash added needs to be. Changing this field will cause the Infusion Volume and Decoction Weight to be recalculated.
Infusion Volume - This field is used to indicate the amount of water that will be added to hit the temperature specified by the Final Temp field. Changing this field will cause the Added Temp of the water to be recalculated.
Decoction Weight - This field is used to indicate the mass of the mash that will be removed, heated and added back to the mash to hit the temperature specified by the Final Temp field. Changing this field will cause the Added Temp of the decoction to be recalculated.

Buttons

Recalc - Click this button to perform calculations.
Ok - Click this button to exit the calculator.

Procedures

Calculating Initial Strike Water Requirements - The calculator can be used to determine the amount of initial strike water required to reach a mash temp. This is done by following these steps:
1. Enter the Malt Weight. This is the total amount of grain being mashed.
2. Enter the Malt Heat Capacity.
3. Enter the Water Volume as 0 (since there has been no water added so far).
4. Enter the Current Temp. This is the temperature of the grain currently.
5. Enter the Final Temp. This is the temperature you want the mash to end up at.
6. Enter the Added Temp. This is the temperature of the water that will be added. If you wish to use a certain mash thickness and have the calculator to tell you the temperature of the strike water to use, skip this field and enter a value in the Infusion Volume field.
7. Enter the Infusion Volume. This is the volume of water that will be added to reach the indicated final temperature. Changing this value will cause the Added Temp field to be recalculated.
The calculator should now be indicating the Infusion Volume and the Added Temp required to hit the Final Temp.
Calculating Step Infusion Water Requirements
1. Enter the Malt Weight. This is the total amount of grain being mashed.
2. Enter the Malt Heat Capacity.
3. Enter the Water Volume. This is the total volume of water that has been added so far.
4. Enter the Current Temp. This is the temperature of the mash currently.
5. Enter the Final Temp. This is the temperature you want the mash to end up at.
6. Enter the Added Temp. This is the temperature of the water that will be added. If you wish to add a certain volume of water and have the calculator to tell you the temperature the water should be, skip this field and enter a value in the Infusion Volume field.
7. Enter the Infusion Volume. This is the volume of water that will be added to reach the indicated final temperature. Changing this value will cause the Added Temp field to be recalculated.
The calculator should now be indicating the Infusion Volume and the Added Temp required to hit the Final Temp.
Calculating Decoction Mash Requirements
1. Enter the Malt Weight. This is the total amount of grain being mashed.
2. Enter the Malt Heat Capacity.
3. Enter the Water Volume. This is the total volume of water that has been added so far.
4. Enter the Current Temp. This is the temperature of the mash currently.
5. Enter the Final Temp. This is the temperature you want the mash to end up at.
6. Enter the Added Temp. This is the temperature of the decoction when it is added back to the main mash. Typically this is the boiling temp of water where you live. If you wish to decoct a certain mass of the mash and have the calculator to tell you the temperature the decoction should be when added back, skip this field and enter a value in the Decoction Weight field.
7. Enter the Decoction Weight. This is the mass of the mash that will be decocted and added back to the mash to reach the indicated final temperature. Changing this value will cause the Added Temp field to be recalculated.
The calculator should now be indicating the Decoction Weight and the Added Temp required to hit the Final Temp.

Formulas

Here are the formulas used by the Mash Temp Calculator. The units used in these formulas are irrelavent so long as they are consistant. The formulas are based on masses, and so return all infusion water/decoction values as a mass. Working with metric here is very helpful since 1 kg of water = 1 liter.

Basic Formula

The following formula will compute the final temperature of a mixture of two masses at different temperatures.

Tf = (Hc1*M1*T1 + Hc2*M2*T2)/(Hc1*M1+Hc2*M2)

Where:

Tf = final temperature
Hc1 = heat capacity of first mass
M1 = wieght of first mass
T1 = current temperature of first mass
Hc2 = heat capacity of second mass
M2 = weight of second mass
T2 = current temperature of second mass

Rearranging this formula, and using a value of 1 for the heat capacity of water, we come up with the following:

Infusion Formula - Amount of Initial Strike Water

The following formula will compute the mass of initial strike water required to hit a certain mash temperature based on the temperature of the initial strike water.

Ma = Hcm*Mm*(Tf-Tm)/(Tw-Tf)

Where:

Ma = required mass of initial strike water
Hcm = heat capacity of malt (about .4)
Mm = mass of malt used
Tm = current temperature of the malt
Tf = final temperature desired
Tw = temperature of initial strike water

Infusion Formula - Temperature of Initial Strike Water

The following formula will compute the temperature of the initial strike water required to hit a certain mash temperature based on the mass of the initial strike water.

Tw = (Ma*Tf-(Hcm*Mm)*(Tm-Tf))/Ma

Where:

Tw = required temperature of initial strike water
Ma = mass of initial strike water added
Tf = final temperature desired
Hcm = heat capacity of malt (about .4)
Mm = mass of malt
Tm = current temperature of the malt

Infusion Formula - Amount of Step Infusion Water Required

The following formula will compute the mass of the water required to boost a mash from one temp to the next.

Ma = (Hcm*Mm+Mw)*(Tf-Tmash)/(Tw-Tf)

Where:

Ma = required mass of water to infuse
Hcm = heat capacity of malt (about .4)
Mm = mass of malt
Mw = mass of water already in mash
Tf = final temperature desired
Tmash = current temperature of the mash
Tw = temperature of infusion water added

Infusion Formula - Temperature of Step Infusion Water Required

The following formula will compute the temperature of the water required to boost a mash from one temp to the next.

Tw = (Ma*Tf-(Hcm*Mm+Mw)*(Tmash-Tf))/Ma

Where:

Tw = required temperature of infusion water
Ma = mass of water infused
Hcm = heat capacity of malt (about .4)
Mm = mass of malt
Mw = mass of water already in mash
Tf = final temperature desired
Tmash = current temperature of the mash

Decoction Formula - Decoction Mass of Mash Required

The following formula will compute the mass of the mash that must be decocted, heated and returned to the mash to boost it from one temp to the next.

Md = (Hcm*Mm+Mw)/(1+((Tf-Td)/(Tmash-Tf)))

Where:

Md = required mass of decoction
Hcm = heat capacity of malt (about .4)
Mm = mass of malt
Mw = mass of water already in mash
Tf = final temperature desired
Td = temperature of decoction when added back to mash
Tmash = current temperature of the mash

Decoction Formula - Temperature of Decoction Required

The following formula will compute the temperature the decoction must be when returned to the mash boost it from one temp to the next.

Td = Tmash-(Hcm*Mm+Mw)/Md*(Tmash-Tf)

Where:

Td = required temperature of decoction when added back to mash
Tmash = current temperature of the mash
Hcm = heat capacity of malt (about .4)
Mm = mass of malt
Mw = mass of water already in mash
Md = mass of decoction
Tf = final temperature desired

Fudge Factor

When adding either hot water or decoctions to boost your mash temp, you must always take into account the amount of heat your mash tun will absorb. Typically, this will only be 1 or 2 degrees fahrenheit, but will vary from system to system. After a little trial and error, you will become familar with the temperature drop realized by your system and will be able to adjust for it.

Errors???

I hope these formulas are useful in your brewing endevors. If you find any errors, please, please, please let me know so I may update this page.

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Last Updated: 25-JAN-99