Hello, Last year I stopped using my 10 yr. old Gaggia Dandy and bought an Isomac TEA. It's very silimair to the ECM Giotto and WEGA, etc. I noticed less flavor in the shots from the new macine and thought maybe water temp's were the culprit. Reading Schomers' espresso trials and tribulations I decided that after a while I would try meas. the brewing water temps. as he described. I finially located an old Fluke Thermometer and began meas. water temperatures. I found some curious things that I did not expect and some things that raise questions/concerns. My older machine heats water to about 180-182 F but temps drop fast after 6 sec. due to the boiler being small. By the end of a 15-20 sec. shot draw temps. are around 165 F or lower. So my feeling that the water temps of my Gaggia were going to be very high due to it's design were wrong. My feelings of more flavor were due to sagging water temps. throughout the draw. The Isomac water temps were around 184 F and these held for at least 15 sec or more before they began to drop. While the bigger bolier and heating element along with the better E-61 group head gave a more consistent shot the temps were far below the 200 F range that Schomer advocates. The Isomac has a thermostat that allows adjustment. I was able to get my water temps up to 194-196 F and could go even higher BUT with higher temps comes higher steam pressure readings. The 196 F water temps were putting the steam pressure readings in the 1.8-2.0 bar range. Far above the 1.4 bar reading the machine was defaulted to at the factory. The gauge maximum is 2.5 bars. Clearly the semi-pro machines either are not meant to work with 200 F water temps or the boilers can handle a higher pressure despite the gauge readings. Has anyone else measured their espresso machine brewing water temps? Has anyone found Schomer's 200 F temps to be better or worse than what they had been using? Lastly, what is a safe boiler pressure to maintain without blowing up the boiler? I am sure there is a pressure relief valve that prevents this but it would be nice to know anyway. GerardFF homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Hi Gerard, There's a mass of information on espresso temperatures posted on alt.coffee. You can usehttp://groups.google.com/to search for it; or you can post your question there. One item -- it's not easy to get accurate temperature readings unless your fluke has a thermocouple you can insinuate into the portafilter. It may be that you're reading low due to very fast heatloss. If that's not it, there may be a problem with the heat transfer from the boiler to the heat-exchanger, since most commercial machines get to 200 F brew temperatures with boiler pressures from 1.5 to 1.7 bar. Scaling is one possibility. Hope this helps Jim Schulman |
Hi: Gotta bunch of questions and comments to throw at you. They's imbedded in yo text. At 02:11 PM 12/30/2001 -0500, you wrote: <Snip> Did you do this precisely as Schomer did, by putting the thermocouple bead inside of your portafilter, just below the top surface of the coffee? This is a real pain in the yass to do, but essential in order to get meaningful results. <Snip> did you check your Fluke's calibration before starting. If you are near to sea level, boil some distilled water (get it from the grocery store) and check your probe. Should read 212F or 100C. This isn't a hard and fast temperature, as the water boiling point is a function of the ambient pressure, but I would think that your Fluke ought to be within a degree of 212. <Snip> Your assumptions aren't correct here afaik. The published temperature of water at 1.433 bars of pressure is 110C, which is 230F. That's more than enuff temperature. AFAIK your first shot should be way over the correct temperature if your machine has been sitting idle for a while. This is because the water in the heat exchanger will have equilibrated with the temperature of the water in the boiler. Your machine has an E61 type grouphead doesn't it? That means that the grouphead should end up being quite hot as well. <Snip> I did an extensive set of measurements of my Rancilio Silvia. They were published on alt.coffee last February. <Snip> Schomer's 203F worked quite well for me. My Silvia's temp stability is +- around 2 degrees F as I recall. That's pretty good for stability, but it ain't a La Marzocco. So I can't make taste comparisons for intervals smaller than 2 degrees. However Schomer's number seems pretty close to right based on my measurements. <Snip> Depends on the design and who makes it. A single boiler machine has to be safe at the pressure that stalls the pump. That could be as high as 18 bar, I guess, since that what people claim that the pumps are capable of (even though we know that the pressure is around 9 bar for a proper shot). The heat exchanger within a HE machine has to withstand similar pressures, but the boiler surrounding the heat exchange does not need to withstand the pump pressure. Even so, manufacturers can't have boilers exploding, so I bet they're designed for worst case scenarios of malfunctioning pressurestats. But I wouldn't advise exploring this firsthand. I'd check your thermocouple calibration, insure that your probe is just below the level of the coffee in the portafilter and try again. By the way, your thermocouple needs to be very tiny or you won't get decent measurements. Any thermocouple junction sheathed in a probe will not give you the right answer because the junction temperature will lag behind the temperature of the process as you are pulling a shot. <Snip> homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |
Greg, Thanks for the info. In myhaste to get my machine "dialed" in better I blew off the instructions of my probe. After reading your post I figured I better go back read them. So I went back and found that I had the wrong probe selected in the menu. And low and behold I am now in the exact opposit camp, my water is now too hot. I did not have any distilled water to use for calib. but I will try it later. Boiling tap H20, I found that the temps fluctuate a bit anyway and decided to try my luck at it. So now my thermostst is turned way down and I now have a steam anemic machine, (now I know why the Giotto is steam anemic). Thanks. Gerard homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast |