I have just bought a Scace I Thermofilter and am having a problem using it.

BACKGROUND
In an effort to achieve more consistent results in my preparation of espresso, I would like to develop a shot preparation procedure that:
1. Reduces the temperature variation of the brew water from shot to shot; and
2. Reduces the temperature variation of the brew water during the brewing of each shot.

I use a Mazzer Mini E grinder, 18 gm dose into an 18 gm VST basket, and a Breville BES900 double boiler (DBD) machine. During a typical 30-sec pull that results in a good tasting espresso (at least, I like it!), the pressure gauge on the BDB reads 9 BAR and I get approximately 36 gm of espresso.

My Scace I is connected to an Omega HH378 thermometer and datalogger. The HH378 records the temperature data once per sec, stores up to 16,000 data points, and can transfer the data to a computer.

PROBLEM
I have installed the Scace into a Breville bottomless portafilter and inserted it into my DBD. The DBD temperature set point is 201 deg. F. According to what I have read on this forum, during a simulated 25 +/-5 sec pull, the amount of water that passes through the Scace should be about 75 ml. Also, the pressure should be about 9 BAR.

During my simulated pulls with the Scace, I consistently see only 8 +/- .25 BAR of pressure (on the DBD pressure meter) and 60 +/1.5 ml of brew water (in a graduated cylinder). According to the Scace, 12 sec into the pull (with 6 sec of pre-infusion) the temperature of the brew water reads 200 +/- 2 deg F. Since the pressure and volume of these simulated pulls do not represent my actual brewing conditions, I am hesitant to proceed with my experiments.

I would really appreciate some input on the following: 1. Should I ignore the differences and proceed; 2. Try to determine if there is a problem with the Scace (e.g., flow rate); or 3. Adjust the OPV of my DBD.

Thanks

I ran these tests a while back on my 900 BDB. I got 78 ml in 30 sec with Scace w 8 bar showing FWIW.

Thanks for the information. There certainly is a large difference in the amount of brew water between your BDB and mine with the Scace in place. Do you recall what your pre-infusion and temp settings were? Also, does your BDB read about 9 BAR when you pull shots?

May want to have a look at this article: http://nic.steve-tek.com/?page_id=500

WayneW wrote:Do you recall what your pre-infusion and temp settings were? Also, does your BDB read about 9 BAR when you pull shots?

Sorry, I don't remember but I think I just did manual mode w/o preinfusion for the purpose of the test. Yes, it reads around 9 bar typically on shots. I found my machine tested around 1-2 degrees cooler than indicated, and was consistent if you followed the same procedure every time. Tended to be cold nosed prior to first shot, then was consistent afterwards.

WayneW wrote:During my simulated pulls with the Scace, I consistently see only 8 +/- .25 BAR of pressure (on the DBD pressure meter) and 60 +/1.5 ml of brew water (in a graduated cylinder). According to the Scace, 12 sec into the pull (with 6 sec of pre-infusion) the temperature of the brew water reads 200 +/- 2 deg F. Since the pressure and volume of these simulated pulls do not represent my actual brewing conditions, I am hesitant to proceed with my experiments.

<snip>

I would really appreciate some input on the following: 1. Should I ignore the differences and proceed; 2. Try to determine if there is a problem with the Scace (e.g., flow rate); or 3. Adjust the OPV of my DBD.

It's worth noting that the Scace thermofilter simulates puck resistance reasonably, but you should not take its simulation too literally.

Depending on the type of espresso (i.e., ristretto, double, lungo), its flow rates may be faster or slower than during a real extraction. In the majority of cases, it doesn't matter since the thermofilter was designed with calibration of commercial espresso machines in mind. That is, temperature or pressure variance may be problematic for a consumer espresso machine with a tiny boiler and vibratory pump, but commercial espresso machines vary very little thanks to their much larger boilers and rotary pumps.

To your question, I think you should ignore pressure measurement differences between the Scace and the onboard brew pressure gauge. Onboard brew pressure gauges are accurate for static measurements, but less than perfectly accurate for flow measurements because the tee is invariably upstream of a gicleur so it reads high (an exception would be grouphead-mounted gauges like the La Marzocco Strada). Even if that were not the case, fretting over 0.5 bar one way or another is silly. Unless you're calibrating espresso machines for competition, it's better to learn how pressure affects the extraction by taste after having used the portafilter/onboard gauge to get it in the ballpark. Threads like Brew pressure and its effects on espresso and Effects of brew pressure on taste of espresso and many others elaborate on this point (search on "brew pressure effect on taste").

As for temperature, that's another matter. The thermofilter is ideally positioned to measure the actual temperature in the brew chamber and I take its measurements as indisputably correct versus a PID setting, which typically is based on the setting on the boiler itself, far far away from the brew chamber. With proper calibration, as is the case with the Breville Dual Boiler, PID readouts accurately reflect the starting brew temperature, but once the extraction starts, the temperature dynamics are too wide for it to accurately reflect the realtime temperature during extraction.

PS: For those following this thread, please see Wayne's similar question on CoffeeGeek to avoid needlessly repeating previous suggestions/comments.