Just as explained in The Master Guide, our brew day begins when we add water to the kettle (our stock pot.)
Adding the Water
The Calculator we have completed tells us "Water Required is..." 18.49L. Our, "Approximate Mash Volume," shows a figure of 20.13L so if we added all 18.49L to our kettle, it is likely that when we add our grain, the kettle will overflow.
To avoid this, I am going to only initially add 15L of the 18.49L required. Using my 5L measuring jug, I will add 15L to the pot and apply maximum heat to it. You can of course, speed up this process a little by adding say 10L to the pot and boiling the last 5L in your domestic kettle and then adding it to the pot as it heats up.
Heating the Water to, "Strike," Temperature
Our recipe asks that we mash (soak) the grain at a temperature of 65°C. As explained in The Master Guide, when we add our grain, the temperature of our water drops by a few degrees. To compensate for this we heat our water to, "strike," temperature. For Mini-BIABs we recommend a strike temperature of 3°C above mash temperature. For our APA we therefore need to heat our 15L of water to 68°C. Regularly stir the water and check the temperature while waiting for it to reach strike temperature.
Adding the Bag and Grain
As soon as your water has reached 68°C, slip your bag into the pot and secure it firmly around the rim of the pot.
Now slowly, "rain in," the grain. To do this, hold the container of milled grain above the pot and slowly pour it in while gently stirring the mash around to submerge the incoming grain.
Here is a picture of raining in the grain...
Once you have added all the grain, we'll add the remaining 3-odd litres of water to fill the pot right up, however we need to know what temperature it has to be at, so give a further brief stir and then check the temperature reading. It is very likely to be within a degree or two of your desired mash temperature, this is great and if so, add the additional water at the mash temperature, if the mash is slightly cooler than the target add hot water etc.
Stir again then remeasure the temperature. If the mash is slightly hot, just leave the lid off the pot until the mash reaches the desired temperature. If it is too cool, apply heat while continually stirring the mash until mash temperature is acquired.*
You have a couple of options now, either leave the pot uninsulated and add some heat occasionally as it cools down, or insulate the pot with a jumper/ towels/ doonah as per Beachbum
You must always stir the mash when applying heat otherwise your bag will burn.
I prefer to just insulate the pot while it is mashing, I find temperature losses are only a degree or so if well- insulated, that is fine in most circumstances.