Water volume for partial mash

I'm going to attempt a partial mash recipe. I'm planning on using my boil kettle with a grain bag.

The recipe calls out something like 3 gallons of water for the mash and then topping off the water after sparging to get a set pre-boil volume. Since my kettle is big enough, couldn't I just mash with a volume of water closer to my boil volume and reduce the amount of top off water?

Or is there some sort of chemistry voodoo going on the the water-to-grain ratio that must be followed?

 

Generally, your water to grain ratio for any kind of mash should be somewhere between 1.25 qt/lb to 2.0 qt/lb.

 

The pH of water is about 7.0. This can vary to more acid or alkaline depending upon your water source. Tannin extraction form grain hulls is a combination of temperature and pH. A combination of a pH of about 6.0 and higher with a temperature near or over 170° can extract the tannins.
The water to grain ration ArcaneXor mentions in his post will keep the mash pH closer to the ideal of 5.2 to 5.4.

 

are you actually mashing or are you steeping?

 

The recipe is the "Speckled Heifer" partial mash kit from NB. I guess when in doubt I'll just follow the instructions.

Correction: recipe calls for 5 quarts strike water and 5 quarts sparge water.

 

The Speckled Heifer is very good. I mashed at 152° to 154° which gave the beer a little more body. Temp was accidental. Had some problems controlling the temp. In a side by side taste test everyone, four people, liked the extra body.