Sparging

When sparging for a partial mash is it better to sparge until you reach a specific gravity or is it better to use all of the water you heated up based upon 2 quarts for every pound of grain? Also, what is the best book you have run across for partial mashing?

Thanks
Dan

Two things to think about....well, maybe three...depends on how you look at it.
1. The sugars generated during mashing have only slightly varying solubilities with respect to temperature. It is the physical extraction from the spent grains goop that requires the extra water.
2. Other components released/produced in the mashing process are more temperature dependent with respect to their water solubilities (ie the tannins, proteins, unconverted starches....).
3. The flavor/feel/head/color/clarity/..... of the beer is dependent upon how much of these other components you extract into your wort. Many recommend avoiding high temp, high volume sparges (that people like me are always tempted do to so as to get every last ounce of beer potential) since these tend to result in woody tastes. And, in the end you have to spend time and gas ($) to boil off extra water which really yielded very little extra beer.

I use the highly scientific method of tasting the sparge run off until it doesn't taste 'sugary'

I sparge until I have six and a half gallons in the boiler. This gives me just shy of five in the fermenter, and as long as I end up with that, I don't usually care about the rest. And with eight to ten lbs of grain, my sparge corroborates the "highly scientific method" mentioned above.

happy run-off,
jp