mjbell said:
The instructions in the kit suggest 170 degrees for 30 minutes. I have read and heard that 150 degrees was the proper temperature,
With deeply roasted or crystal grains, the malt is "dead" meaning no enzymes, meaning no possible conversion of starch to sugar. That conversion is already done by the maltster and the kilning schedule. So the brewer need only steep those grains to get the flavor and color out. So below 170F is decent, generic advice.
150F is also decent, generic advice since you're just steeping. With partial mash, however, you're now mashing yourself, and converting the remaining grain starches in "live" malts to sugars, and that requires more precise temperatures, that you get to pick in order to shape the "maltiness" profile you want. If you want a bigger, rounder mouthfeel, i.e., more body, then mashing 156 to 158F creates more sugars that don't ferment out completely, leaving more body. 148 to 150F creates simpler sugars that the yeast can fully eat, leaving a drier finish and less body.
This is the "control" that all-grain brewers speak about: they can shape the entire sugar profile, whereas partial mash shapes only a portion. And pure extract controls none; you're stuck with whatever Briess or Munton's did weeks ago at the extract plant.
Partial mash makes virtually any beer style possible with little more equipment than basic extract brewing, and will introduce you to the brewing process of maintaining that more precise temperature for 30 to 60 minutes. Once you have that licked, you buy bigger pots and go all-grain for total control. Or stick with partial and have more free time on weekends.