Hey Guys
Matti - I usually mash my porters at 64-66C (used to do it at 68C, but they were too heavy to drink all night), actually, I mash all my beers at that temp, though the lower the OG, the closer I get to 70C, like a 1032 bitter I will mash at 70C, and my 1110 Russian Imperial Stout I will mash at 64-65. I always perform a mashout to 75C, but usually only hit 72-74. I have only just started fly sparging again, after batch sparging my last 40 odd batches, and I was/am under the impression that the grain bed should be around 75C when sparging. The reason being, the maltose is a sticky solution, and it is easier to get it out the hotter it is (within reason), much the same as it is easier to pour warm honey, rather than cold honey, if you get me. The tannins will come out over 75C, I always thought, but I could be wrong. There is alot about water chemistry I dont know, and am trying to learn (I will be picking your brain next BJCP Kieth!!!), but there is alot of buffering power in the malts, and tannins will be leached out if the pH is too high(?) That is why decoction mashing doesnt extract tannins, where you remove 1/3 of the grains, and boil them, it all has to do with pH and buffering power. When you start to sparge, most of that buffering power in the wort is lost, and as you get progressively weaker gravity in the liquor still covering the grains, the pH will start to rise, and leach out tannins and astringeny, which is also what happens at too high a temperature, hence why I thought I had sparged too high. I believe you want to aim for a mash pH between 5.1 and 5.5 measured at mash temps. The more dark malts you have, the lower your mash pH will be.
Pedro - I understand the reason behind mashing out, but am still feeling out the intricacies of water chemistry, as you have probably just read. I stick a candy thermometer into the middle of my grain bed to keep an eye on the temp in there, and I also have a bimetal thermometer in my HLT, so I am reasonably confident the numbers are fairly accurate, though, as Weizguy has told me on numerous occasions, my thermometers may not be completely accurate, as they are only cheapies. As far as sparge water pH goes, I have only just received a water quality analysis from the local water supplier, they dont publish the info ANYWHERE, and the analysis they did send me was from 2004, which is disappointing, but the lady assured me it was pretty much the same. It is very soft (though tastes bloody awful) and has a pH of 7.2. Should I somehow acidify this water before sparging with it? This could be the reason I found it to be more astringent than usual, as I am usually only batchiung, and the wort should still have sufficient buffering power. I havent ever tested the final runnings, as I attach my pump to a hose that goes straight in the tap on the kettle, so it will be a real pain in the freckle to take it all off for a gravity check. I sparge very slowly, taking 50 mins to get 30L into the kettle, and plan on taking over an hour for my RIS tomorrow. I have tried the beer since, and it has come up quite well, but I didnt think to taste the brown scum ring, I will do that next time though, thanks for the tip. It more than likely was the hops, but at only 25IBU, it seems unlikely. Who knows? All I know, is that the beer has come up alright, and I am learning a hell of alot on this thread. Do you think I should adjust the pH of my sparge water, even though I wont be sparging to less than 1006, or should it be OK?
All the best, and apologies for the long post
Trent