# Rest Temperature

Calculates boiling water volume needed to raise mash temperature for step mashing.

## How to Use

Enter the following values and the tool instantly calculates how much boiling water to add:

| Input                      | Description                                                                                                       |
| -------------------------- | ----------------------------------------------------------------------------------------------------------------- |
| **Current Temperature**    | The current mash temperature (measure after stirring well)                                                        |
| **Target Temperature**     | The desired next rest temperature                                                                                 |
| **Boil Temperature**       | The temperature of the water you will add (typically boiling)                                                     |
| **Mash Water Volume**      | The volume of water currently in the mash                                                                         |
| **Grain Amount**           | The total weight of grain in the mash                                                                             |
| **Mash-Tun Heat Capacity** | Your mash tun's heat capacity in L equivalent water volume (use the Mash-Tun Calibration tool to find this value) |

### Output

The tool displays the volume of boiling water to add to reach your target temperature. The result accounts for heat absorbed by the grain and heat lost to the mash tun.

## About Step Mashing

Step mashing involves resting the mash at different temperatures to activate specific enzymes and achieve desired wort characteristics. Adding boiling water is one method to raise the temperature between steps.

## When to Use This Tool

Use for:

* **Multi-step mashes**: Protein rest, saccharification steps
* **Mash out**: Raising to 168°F to stop enzyme activity
* **Temperature corrections**: Fixing low mash temperatures
* **Decoction alternative**: Simpler than pulling grains

## Common Mash Steps

### Acid Rest

* **Temperature**: 35-45°C (95-113°F)
* **Purpose**: Lower pH, improve clarity
* **Duration**: 10-20 minutes

### Protein Rest

* **Temperature**: 45-55°C (113-131°F)
* **Purpose**: Break down proteins
* **Duration**: 10-20 minutes
* **Good for**: Wheat beers, pilsners

### β-Glucan Rest

* **Temperature**: 37-45°C (98-113°F)
* **Purpose**: Break down gums
* **Duration**: 10-20 minutes
* **Good for**: High wheat/oat beers

### Saccharification Rests

* **β-Amylase**: 60-66°C (140-150°F) - fermentable sugars
* **α-Amylase**: 66-71°C (150-160°F) - body/dextrins
* **Duration**: 30-60 minutes each

### Mash Out

* **Temperature**: 76-77°C (168-170°F)
* **Purpose**: Stop enzyme activity
* **Duration**: 10 minutes
* **Benefits**: Easier lautering

## Calculation Factors

### Heat Capacity

* Water: 1.0 BTU/lb/°F
* Grain: 0.38 BTU/lb/°F
* Combined mash: \~0.2-0.3 BTU/lb/°F

### Volume Limitations

* Mash tun capacity
* Each infusion thins mash
* Plan steps accordingly

## Example Calculations

### Example 1: Protein to Saccharification

* Current: 50°C (122°F) with 15 liters (4 gallons)
* Target: 67°C (152°F)
* Boiling water needed: \~9.5 liters (2.5 gallons)

### Example 2: Saccharification to Mash Out

* Current: 67°C (152°F) with 23 liters (6 gallons)
* Target: 76°C (168°F)
* Boiling water needed: \~7.5 liters (2 gallons)

## Tips

* Have boiling water ready before starting
* Add water slowly while stirring
* Check temperature frequently
* Account for mash tun capacity limits

## Advanced Techniques

### Combined Step Mashing

* Infusion + direct heat
* Best of both methods
* More flexibility
* Requires right equipment

### Reverse Step Mashing

* Start high, cool down
* Add cold water or grain
* Less common method
* Special applications

## Using with Recipe Planning

* Calculate water volumes needed for your mash schedule
* Plan total water usage for multi-step mashes
* Account for mash tun capacity limitations
* The tool remembers your last entered values

## Mash Schedule Planning

### Two-Step Mash

1. Protein Rest: 50°C (122°F) for 15 min
2. Saccharification: 67°C (152°F) for 60 min

### Three-Step Mash

1. Protein Rest: 50°C (122°F) for 15 min
2. β-Amylase: 63°C (145°F) for 30 min
3. α-Amylase: 70°C (158°F) for 30 min

### Hochkurz Mash

1. Brief rest: 62°C (144°F) for 30 min
2. High rest: 72°C (162°F) for 30 min
3. Mash out: 76°C (168°F) for 10 min

## Related docs

* [Mash Profiles](/profiles/mash.md)
* [Recipe Designer](/recipes/designer.md)


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