gscace wrote:Andy's comment and Terry's as well hit the nail on the head. It's about coffee taste. The thermofilter's role is in quantifying the temperature profile that produces the best possible taste, whatever that profile happens to be. Once you've got it nailed, you can make the measurements that help insure that you can nail it again, from technique training to machine setup to quality control programs etc. It's important to keep an open mind about profile, but I'll say that whatever the profile happens to be that produces mind blowing espresso, the ability to hit that profile time after time is paramount.
-Greg
Although my previous post of Geoff's La Marzocco profile was a quick look at the boiler temperature calibration aspect of the thermofilter, after reading Greg's comments, my interest took another tack. One of the most important goals of the buyer's guides and how-tos on this site is to provide steps on getting the most out of a given machine under the home barista's real world constraints. The biggest constraint is time. My weekday mornings are probably like other espresso lovers -- we want the best possible shot in short order. There's little if any time for retries.
Temperature profiling helps tremendously in this respect, not only in showing how the brew temperature development affects the espresso's characteristics, but also in getting the magical "first shot, best shot" experience. I think this point is hard for professional baristas to appreciate; they toss out two or three "garbage shots" just to warm up the group. Ignoring the question of cost, I strive to develop a routine that optimizes the first few shots of the day as a practical necessity of getting to work on time.
To create these profiles in the past, I used the same Fluke 54-II thermometer, but instead of the thermofilter, I ran a thin 36-gauge type T thermocouple wire over the basket's edge to measure temperature, laying the wire straight across the surface of the puck and locking the portafilter in. You can get an idea of what the setup looks like in this
video of a cooling flush. While over the basket approach does work reasonably well, I have to agree with Greg's comment that it's a "pain in the yass". And as others have noted, probe placement can make a significant difference. You can tell immediately if the probe is off because the profile shape will be all wrong... and you must start again with a new puck of coffee. It is very tedious, time consuming work.
I wondered if the thermofilter might shave some time off my HX fine tuning, especially for those precious first shots that demand extra attention. So in the last week leading up to our friendly shootout at Geoff's cafe, I used the thermofilter to map out the initial flush requirements for the A3. Again, my goal was to get as close to fifth shot quality right out of the gate. These heavy group machines need an extra kickstart to get the system to the same temperature, which pro baristas deal with by just running extra shots... so how close could I get to that with flushing alone?
Each time I started with a "very idle" machine, i.e., at least 30 minutes. Elektra is a fine looking lady, but as you can see in the photo below, she doesn't like to be woken up:
A real fire breathing dragon at 6am
My first approach prior to the arrival of the thermofilter was a variation of the technique I applied for rousing the Cimbali Junior out of bed quicker: Flush... wait... flush... wait... flush... pull shot. It helped the first shot, but the second and third were always better. Let's try it another way, and this time I won't have to waste a lot of coffee. My theory was that I could nail the temperature more accurately for the first shot by overcompensating slightly for the first flush. In other words, instead of counting off Chris Tacy's "one Mississippi, two Mississippi... six Mississippi", add a couple extras to warm the group up (just a tad more) and cool the heat exchanger (just a tad more).
I measured the resulting brew temperature for each of the three first "shots" into the thermofilter, adjusting the first flush by small increments. I'm still experimenting with using the thermofilter as a training tool. So far I've learned:
- Flushing for a few extra seconds the first time to compensate definitely helps the first shot. For this machine, add three Mississippis if it is "really really" idle
- Pay attention to excessive "rinse" flushes. I have the habit of running water through the group to clear the dispersion screen. If the next shot is pulled soon thereafter, it affects the next shot's flush time. I know, I know... duh
. Now if I'm pulling successive shots, I hold my OCD tendencies at bay and let the cooling flush handle the rinsing.
These small changes have increased my temperature consistency, so much so that Geoff remarked that it was a non-issue in our shootout. That's high praise considering the capabilities of his gear.
. You are right, the T/C over the lip can be highly unreliable because the placement of the T/C in the basket can affect the reading. There are other problems with it. But when you do 20 measurements and they are all consistently different from the Thermofilter, there is enough there to tell you that the difference is real.
