mash/sparge question (big beer)

I just made my 4th all grain batch, an Imperial Stout with 21 pounds of grain. After mashing at 155 for 60 minutes I added about 2 gallons of 205F water from the HLT to bring the mash upto 170F. I stirred the mash until the entire grain bed was 170 and then let it sit for 10 minutes. I then started to recirculate for about 10 minutes (about 5 quarts). I slowly drained the wort into the kettle. Everytime I do this I always ask myself, "Should I allow all the mash water (wort) drain out of the grain and THEN add sparge water or should I add the sparge water as I am draining the tun?" I do not have a sparge arm I just allow the vinyl tube to drip on top of the grain bed and I try to keep about an inch of water on top of the grain (although the grain floats so i never really know how much water is on top). With this particular recipe I drained the tun and added the sparge water and the wort was thick and black all the way up to 9 gallons in the kettle! My kettle is a 15.5 gallon keg with a 3.5kwatt element that evaporates over a gallon an hour so I usually start with 7 gallons anyway. This time I just boil the wort for about 1.5 hours (until I got down to 7.25 gallons) and then started my 60 minute brew session. The pre boil gravity was 1056 and the after boil gravity was 1098. I ended up with 5.5 gallons in my fermenter. As the wort was boiling I decided to open the valve on my mash tun and "just see" how much drains out. Well I accumulated about 3 gallons of wort! I hated to dump that down the drain. Thoughts, commendations, recommendations on my process?

Doing some quick calculations with ProMash, I figure that you should have gotten about 13 gallons into your brew kettle. This is based in 5 1/4 gallons for the mash and 10 1/2 gallons for sparging. ( A little over 2 gallons absorbed by the grain and you loose a bit in your tun)
Having said that, ProMash gives an OG of 1.104 at 75% efficiency so you are not too far off. Did you measure the SG of the left over wort? If it were above 1.012 or so I would have been tempted to throw it into the kettle and boil it down with the rest of the wort.
If the extra wort has a bit of gravity to it you could also make a smaller batch with it. Who knows, might make a good beer.

Big beers mean plenty of sparging, though it sounds like you did a good job. If you are batch sparging, you drain the bed & refill it. Short of checking the gravity of the last run, I'd say you did well.

By the way, you will probably like the PRA. The corn comes through as a trememdous mouthfeel and a nice tang.

barside laundry said:

I slowly drained the wort into the kettle. Everytime I do this I always ask myself, "Should I allow all the mash water (wort) drain out of the grain and THEN add sparge water or should I add the sparge water as I am draining the tun?"

Click to expand...

If you drain the all the wort out before adding sparge water, then the grain is not supported by the wort and can become compacted. This can cause a stuck (or extremely slow) sparge. If you keep the sparge water roughly level with the grain bed, this doesn't happen. Don't ask me how I know this.
I am also puzzled by your comment that your grain floats, so you can't judge how much sparge water you have above the grain bed. My grain stays on the bottom, and the sparge water lays on the top so it's easy to see how much the water level is above the grain bed. I use a roller mill which leaves the husks pretty much intact, and a sparge arm which adds the water very gently.
From your description, I would suspect that you may be shredding your husks during the milling. (The husks are lighter than water and will float.)

Hope this helps.

-a.

That makes sense! I get my grain crushed at my LHBS and I have heard that he crushes too much.