Sparge means "sprinkle".
The purpose of sparging is to rinse all the sugars out of the mash. In concept, that's really all you are doing - rinsing your grain bed.
It also halts enzymatic activity because alpha and beta amylase become denatured around 170° F. The benefit is if you are really good at mashing you know exactly when to stop so your malt flavor profile is where you want it.
There are a few "right" ways to do it and the measure of how well you sparge depends entirely on the targets you set for the mash. Answering these questions help you decide what method to use:
- How efficient do I want to be?
- How much time do I want to spend?
There are three main methods of sparging: no-sparge, batch and, fly (continuous). The Homebrewing Wiki has a decent discussion of the methods. I'll give you a summary of each.
You should vorlauf before each of these (see below).
No-sparge is exactly what it sounds.
- Drain the mash tun into the kettle
- Top off the kettle to the desired pre-boil volume
It has a few advantages, primarily its simplicity and that you are never in danger of extracting tannins from the grain husk. It is the least efficient, meaning some desirable sugars remain in the grain. The less efficient you are, the more grain you need to use.
Batch sparging is the next simplest.
- Drain the mash tun into the kettle
- Refill the mash tun an inch or two above the grain bed with hot water
- Stir and let sit for a few moments
- Vorlauf again
- Go back to step 1. until you have your desired pre-boil volume
This method is less labor intensive and quicker than continuous sparging. It also eliminates channeling - a concern if you have a single pick-up (like a braided hose) in the bottom of your tun. The efficiency of batch sparging falls somewhere between no-sparge and fly, but is is fairly close to the higher end of efficiency.
Fly sparging works best with an automated system.
- Set up a sparge arm that gently sprinkles hot water on the top of the grain bed.
- Begin draining, or pumping, sparge water through the arm
- Drain your mash tun into the kettle just fast enough to match the sparge water flow rate
- Collect your desired pre-boil gravity, or until the runnings into the kettle get to around 1.010 specific gravity.
Using continuous sparging you can get upwards of 85% efficiency. That means of all the sugars that you could get out of your grain, you extracted eighty-five percent of them. Fly sparging requires another piece of equipment, however it is easy to make. The geometry of your mash tun and the wort pick-up should not promote channeling because the wort is always moving down the grain bed.
Vorlauf
One step that is technically not sparging, but comes between mashing and sparging, is vorlauf. This is simply removing some wort from the mash tun drain and gently returning it to the top. By recirculating the wort you set the gain bed up to filter out husks and other larger particles. Vorlauf increases the clarity of your beer because those bits never make it to the kettle. A pump is the easiest way to do it, but you can use a pitcher, just don't disturb the grain bed. Recirculate until you stop seeing floaties in the return.