Capping a mash

I am planning on brewing a big beer this weekend. I've looked high and low for information on capping the mash, to no avail. Does anybody have any experience with this..what would the procedure be?

My initial thought is this. I will have a MT full of 16 lbs of Golden Promise that will have been mashed and sparged once.....and something tells me there will still be quite a bit of sugar in there. So I was wondering if I could cap the mash by throwing in a couple additional lbs of grain and make a low gravity "lawn mower" type beer .

The other alternative that I thought of would be to sparge through a full additional 6 ish gallons...see what my gravity is and then supplement this with a couple lbs of DME to bring the gravity to an acceptable level.

Thanks,

Of your total grain bill, that third runnings will have a 1/4 or less of the potential gravity points. Designing Great Beers goes into detail on how to calculate this out.

Capping is easy, just throw those new grains in there before you sparge again. Keep in mind the additional water consumption of the new grains. Also, you'll want to stick to crystal malts or other high kilned malts and stay away from basemalts - as you will not be mashing these grains.

And the idea of having DME on hand in case your gravity is too low is spot on. Alternatively you could increase your boil time, but then you'll end up with less beer.

Awesome advice..thank you...I was wondering about that (conversion).

So...just thinking alound here...If my inital gravity for this recipe was 1.072 and I hit it again with another 6 or so gallons...I could expect to get something in the neighborhood of 1.020?

Your kinda doing a party-gyle... Go here and download the simulator.. http://www.braukaiser.com/wiki/index.php/Batch_Sparge_and_Party_Gyle_Simulator
Its really close to what you want.. I got 3 batches out of 18# of grain.. Watered down the first runnings, used the second runnings as they were and added a pound of DME to the third with a little more boil time..