Monday, February 15, 2010


I'm beginning to wonder if having all these temperature probes is a curse, rather than a blessing. I mean, sure, it has been fun learning about them, prototyping, testing, and redesigning the support circuitry, and I have certainly appreciated the chance to rediscover lost talents in electronics and programming. The problem is, I'm not sure that the volume of information I now have at my disposal is helping me address the whole reason I'm doing all this, which is to make more consistent beer.

Sometimes I feel like I'm on the way to a sort of "paralysis by analysis" situation. Take yesterday for example. I brewed a 10 gallon batch of Geordie-Boy and I had temperature probes everywhere. Did they help me? Probably not as much as they confused me. But let's not jump to the finale, I have a lot of ground to cover first.

Stick it where the tun don't shine

While I was cleaning the downstairs utility closet and the garage, I happened to finally identify a "mystery" 20A circuit. It turns out that it runs a single outlet in the garage into which my house's central vac system is plugged. That outlet is in a corner of the garage whose very existence was just a rumor up until two weeks ago, and I had not really factored it into my electric brewing plans to this point.

As you may recall, I have been using two 1500W heat sticks recently to augment my propane burner. They run on separate 15A circuits. When I built the heat sticks, I also acquired the materials for a 2000W heat stick, but since I didn't know where I was going to be able to plug it in, I tabled its final assembly.

Finding the 20A circuit prompted me to finish that heat stick, which of course became a multiple Lowe's trips activity because the 20A 115V outlet was keyed differently from the 20A 240V plug I had originally bought. (Who knew? Except everyone who has ever done actual electrical work before, obviously. For future reference, while they both have the hot and neutral blades at 90 degree angles from one another, the 115V horizontal blade is the opposite side from the 240V one.) Once assembled, the 2000W heat stick was able to raise 4.5 gallons of water from 8 C to boiling in about 90 minutes, uncovered, in an ambient environment of 45 F. Not too shabby as an adjunct heater, but still not enough wattage to go all-electric.

I have been having trouble hitting the right mash temperature, so I decided to heat my strike water directly in the mash tun rather than using a separate propane-fired vessel and risk losing heat during the transfer. I also decided to skip the boiling grits preparation, reasoning that since they were already gelatinized I could get the same effect by just adding them to the strike water as I heated it. (You'll recall I have had problems with the near-boiling grits adversely affecting the overall mash temperature - this way, I figured, at least everything would be about the right temperature at the start. More on this later.) I used hot water from the tap so the actual temperature rise required was substantially less than usual. I used one of the 1500W sticks to get the final 40 or so degrees I needed to get to the strike temperature of 169.5 F.

RIMS is looking better all the time

Here's where the weirdness started. I dropped one of the new active mode temperature probes into the tun at the start of this process and its reading stuck at 39.1 C, which I knew to be lower than the starting temperature of the tap water. No amount of resetting the WebControl board would make that reading budge - in fact, as long as the probe was hot, resetting the WebControl only caused it to not read at all. Once the probe cooled below 39 C (about 102 F) it seemed to work normally.

OK, duly noted, move on to a different probe and mark that one as "refrigerator temps only" for the time being. I switched to one of the parasite mode probes and was rewarded with a more reasonable reading. I happily went on my way, weighing out the grain bill and conducting other normal pre-mash activities, glancing occasionally at the web page that refreshes the probe readings every 20 seconds or so.

After a while, I began to notice that the probe reading didn't seem to be changing very much. I suspected that the reason was a lack of circulation in the water - with the way the heat stick was oriented, it looked likely that a layer of hot water would form near the heating element at one end of the tun. The end of the probe hung down very nearly to the bottom of the tun, so I guess it's reasonable to think that the water down there was not warming as rapidly as the water up top. This is a known phenomenon in the ocean but I had no idea that the vastness of my beverage cooler mash tun would be subject to it as well.

So now I started to periodically stir the strike water. Every time I did this, I was rewarded by a 2-3 degree jump in the probe reading. That's not great, but it's something that I can plan for in the future, and in fact I could probably rig a little agitator to help keep the water homogenized during this process if I wanted to. That's what I need, another time-sucking project. I'll get right on that.

Now the TMI factor starts to weigh in. I noticed a few things that affected my confidence in my measurement setup. First, there's a pretty big latency in the measurements themselves, due to a combination of scan rates on the Arduino and update rates on the display page. I got to the point of trying to guess where the reading was going to be on the next update rather than just accepting it at face value. In reality the maximum drift could only be about 40 seconds. The probes are read in a loop that cycles about every 4-5 seconds. The PC scans the Arduino every 20 seconds, but it only services serial I/O at the end of each loop. The display reloads every 20 seconds, so at worst your reading is less than 40 seconds old, because the worst case timing happens when a display update happens right after a scan, then happens again before another scan finishes its I/O). That's hard to remember when you're intently staring at the screen waiting for the update, and when the screen refreshes you see other values change, but not the one you're monitoring.

Anyway, eventually the tun reached its target temperature of 169-170 F more or less, and I doughed in with the remainder of the grain, stirring it to make sure there were no obvious dough balls. (Side note - I need a longer spoon or a mash paddle - 170 F wort stings a little when your fingers inadvertently dip into it on the down stroke.) I pulled the heat stick out of the tun but left the probe. Turning to the readings, I saw that the probe was showing about 138 F, which was substantially below the 154 F I was shooting for. (And before you ask, yes, I compensated for the grain temperature being at garage ambient when the strike water temperature was set.) The problem was by this time I had zero confidence in the reading on the probe, and I sure wasn't going to sit there and stir that glop until the probe told me the temperature was good, so I yanked it out of the tun and put my trust in the math of thermodynamics. (And before you comment, yes, I'm aware that that is a juvenile reaction along the lines of "la la la I can't hear you.")

After getting the mash started, there really wasn't anything remarkable about the remainder of the batch. I split the sparge water into two volumes and heated each one with a separate heat stick. They were ready way before the mash ended (partially because I started them before the mash started) and I didn't figure a few degrees high was going to hurt so I didn't obsess over their readings as much as I did the mash tun. I did screw one thing up by not closing the valve on the mash tun for a few seconds when I did the second sparge, and because the tubing wasn't in the container I vorlauf to, I'm sure some extra grain particles ended up in the wort. I guess they'll settle out on their own eventually.

I used the 2000W heat stick, a 1500W heat stick, and the propane burner for the boil. I had to rig a wind shield by the burner because the day turned a little blustery, but I had a folding camp table that fit the bill nicely as a 90-degree wind barrier. I scooped off the majority of the foam at the beginning of the boil. I hope this reduces the amount of trub and helps clarify the wort. Chilling was obviously no problem with cooling water and ambient temperature at about 45 F.

Brewed: 100201 Geordie-Boy Ale

I filled two carboys and still had a substantial amount of wort left over. I'm not surprised: I spent more time worrying with and tweaking the temperature readings than I did paying attention to things like volumes. In fact, I didn't even measure the wort volume before the boil or afterward, not because I don't care, but because I was so rattled I forgot. (Where's that Workflow process? Did that get sidetracked by these other BS activities? Fire the developer.)

I used one Better Bottle and one glass carboy. I'm getting a little leery of the Better Bottles because I have a tendency to handle them in a way that causes them to "suck back" through the airlock. I don't think it's me, I think it's just a natural effect of having flexible sides. I put this BB in a milk crate and it seems to be a little more stable.

I am doing an experiment with yeast. In the glass carboy, I used one packet of Danstar Nottingham dry yeast, and in the Better Bottle I used one packet of Safale US-05 dry yeast. I didn't pre-hydrate either of them.

The gravity of this batch was a little low - I measured it at 1.039, down from the anticipated 1.043. Again, if I had spent more time doing useful measurements I might have a clue as to why, but I have a couple of ideas. I'm not sure that I got all the starch from the grits converted correctly, for one thing. When I dumped the spent grains, I noticed there were a few sizable homogeneous grit clods at the bottom of the tun. I doubt they pulled their weight in the mash. Also, with all the angst over the mash temperature, I have no idea if I actually hit 154 or went higher, and without measuring volumes I really don't know if I just oversparged or underboiled.

I guess we'll find out in a couple of weeks if this batch can overcome its humble beginnings to become a fine, upstanding ale. I have it in the inside portion of the basement, where the ambient temperature is in the 60-70 degree range. I have probes strapped to the outside of the bottles. You can see them on the charts as probes A8 and A9. This may be the most useful application of the probes yet - I should have a great strip chart showing the fermentation temperature profile for both yeasts.

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