I brewed a Dopplebock this past weekend. Been doing all-grain for over a year now and this was, by far, my biggest grain bill at 16lbs for a 5.5 gallon batch. Boy was THAT fun to grind all that grain and it start to overflow a 5 gallon homer bucket!
On to my questions:
last two brews I did decoction mashes. First time I missed my temps because I didn't pull enough of a decoction to raise the temps to the desired level. I resorted to adding some boiling water to get it to correct temps.
Saturday, I did a single decoction and the goal was to raise the temps from 158 to 169 with this decoction. I boiled the decoction for some time (30 min+) and then opened the mash tun to dump it in. I waited for conversion using iodine test. Reading here said I should have conversion about 20 minutes, but it took quite a bit longer. Closer to 50 min. My temps in the mash tun dropped 10 degrees, probably due to the fact that I had it only half full and also that I didn't pre-heat. I tried to compensate for that with a higher strike temp, but that obviously didn't work. So, again, I had to resort to mash out at 159 degrees. After that time, everything was converted and since I didn't hit mash out temps at 170, I only waited 5 minutes before I started lautering.
(Grain bill was simple: Weyer pilsner malt, munich I, carared.)
Does a mash-out matter in this case? What I mean is, should my efficiency be the same whether or not I did a mash out, correct? Last two brews I missed my mash out temps and my efficiency was LOWER than when I do a mash out. Also, last two brews I did decoction mashes (and MUCH longer mashes) and I read that usually bumps up efficiency. Not once did the temps go over 160, so enzymes should have been still working.
Grain crush has been the same last 6 brews, and efficiency has dropped from low 80's to low 70's. The only thing different from brews in the past is my water. I now use RO water that I add calcium carbonate to it to get my calcium levels up to snuff. The pH hasn't been a problem and stays in the 5.2-5.6 range. This could, perhaps, be the problem with less efficiency.
I am not worried about it, really, just more curious than anything.
Second question: the two brews within the last few months that I did with 80+ efficiency numbers lautering was VERY slow (45 min to get 7 gallons.) This was mainly because I hadn't finished cutting the slots in the copper manifold I built and I did it a bit fast and got stuck. Initially, I thought that perhaps this slow lautering helped, so I purposefully did it slow on the two lagers that had 70's efficiency. I do batch sparging, if I need more into the boil kettle. Does lautering speed have anything to do with efficiency IF the mash is fully converted?