When making a 5 gal. batch, is there an advantage to boiling all 5 gallons of water for the mash as opposed to just 2.5 gallons then adding cold water after?
I have a 10 gal kettle so can easily boil the whole amount, but the NB instructions generally call for a small boil followed by more topping off.
Is it preferable to maximize the amount of water in the boil and add only what I need to top off the primary fermentor to 5 gallons?
It’s always better to do a full boil when possible. You’ll get better hop utilization. You’re sanitizing all the water that goes into your wort, not just 1/2 of it meaning your reducing the risk of infection. You also incorporate the extract into the water better and not trying to blend it together later, which in return will give you a better hydrometer reading.
Boiling with less water may also affect (effect? affect? I always get this wrong) the final color of your beer. I’m not certain, but a boil with less volume would have a higher gravity and thus more sugar, which I assume would caramelize or darken easier. I could be completely wrong here and overthinking it.
But, full boils are pretty much always recommended over partial boils whenever possible.
It you need to cool quickly without a counterflow you can use a immersion chillers with a aquarium pump to recirculate ice water. That combined with an ice bath got me down to 60F in about 20 mins. I
You can also put a lid on the boil pot and let it cool. Or, 1 person on this board drains his wort (even lagers) into corney kegs to cool. Pitching the yeast sometimes weeks later.