So, Jody came up the other day and we brewed up a Porter in the garage. Inspired by James Spencer and the current science experiment he's got going on over on Basic Brewing Radio (podcast..) we decided to measure a few things while doing up our brew. First, we measured the specific gravity in Brix at several points during the mash, to see how the O.G. went up, down or stayed the same. Of course we figured it would go up, sure. but I was sorta surprised by how much this went up. Here's the graph:
So, again, measurements for the mash sugars were measured in Brix for sake of simplicity, repeatability and not having to screw with the extra layer of temperature correction, since we measured on my ATC refractometer. If you do the math (ok, I'll do it for you.. ) you can see we started off at something around 23.6 Brix when we finally got the temp stabilized at the 153 degrees F we wanted. We used the pump to recirculate the mash fully before each reading, and then we just ran off some wort into a pyrex jar and took our sample from there. Then we measured at various points along the way until an hours time had passed.. and strangely, the curve still hadn't flattened, meaning that either it was just going to keep going for a bit more or maybe just take a steep nose dive in it's climb and flatten out. Who knows? An hours mash time is plenty for this kid any day of the week. The difference in the original reading and the end of the house reading is 0.014 Original Gravity points, for those of you not into the Brix/Plato thing. That's not insignificant. It loks like from the moment of mash in, to about the half hour mark, you get the most bang for the buck (time) spent.. but if you need another point or point and a quarter, spend the extra half hour in the mashtun and then start running off. It looks like only about a point and change was gained after the 30 minute mark, which translates to 0.004 O.G. points or so.. it's something to consider, I guess.
An interesting thing happened here during this brew. Now, normally, I calculate for 82% brewhouse efficiency here at Second Shift Brewing.. but I normally only do a half hour long mash, then start my sparge. The results I get are good, and I base this half hour mash time off the new info that's getting kicked around which seems to indicate the vast majority of the starches are converted by around the 20 minute mark. So, I round that off to half an hour and call it OK. The interesting thing was that we had calculated this thing for a 1.058 O.G. beer.. but in the end, we came out with 1.063 O.G. I was puzzled at first by this, because I rarely miss my mark by that much.. but apparently, this hour long mash increased my brewhouse efficiency so much, it skewed the numbers right up and off the chart for this beer. So, Jody.. that's gotta be the reason why that happened. This occurred to me in the car ride this morning after I dropped off the kids. :)
Here's another chart for you:
This one is the readings we took on the wort that was draining from the mashtun into the boil kettle. We took readings on the wort as the kettle filled up, so the Galons of Water Sparged on the left side is the amount of wort that was in the kettle when we pulled a sample from the hose as it was flowing into the kettle, and the bottom line there is the poins in Brix (labeled incorrectly as Plato.. rats!). As you can see, the tun was originally running out at nearly 25 Brix at first, but as the sparge continued, we measured about 4.8 Brix at the 10 gallon filled level.. and we finished out at 2.5 Brix when we actually had our entire pre boil volume of 13.6 gallons. This info would be useful to know if, say, you wanted to do two beers from one batch of grain.. and you could gather the first 3.0 gallons or so of super high gravity wort, add a bit of plain water for evaporation losses, and boil and add hops to that on the stove top, while grabbing the rest of the wort of lower gravity stuff and doing up a regular strength beer from that in a normal sized boil kettle. I'd do this and fill my mini keg up with barley wine for the winter and be happy with that, since I could ferment it in a standard 5 gallon glass fermenter and probably not have any overflow issues. FYI, this was a 24lb grain bill that this came from.
Wow, I'm spent! Too much long head stuff there.. good job Jody, couldn't have gathered this data without you! Speaking of Jody (the head brewer over at Blue Label Brewing) I believe he said they were offering a free beer sampler over there with your purchase of enough gas to get to his tasting room, and no more strings attached. Drop in and tell him I said hello!
