I have been wanting to this for some time, probably from the time I purchased the machine. With non-E61 heat exchange machines, measuring the temperature of the brew water is not the easiest or the cheapest task. I tried googling the subject to see if anyone else has done this test so I can simply copy their routine but the information I found was mostly for the Oscar and not the Musica and even that didn’t make me feel comfortable or didn’t make sense. My challenge was that I needed to determine a cooling flush that would get me somewhere between 197F to 200F to be exact. Why the lower-ish temperature? I mostly use medium and dark roast coffees and for those, a lower temperature is ideal.
I started by purchasing a thermocouple thermometer and luckily I found a brand new AMPROBE T-51 on eBay for under $35!
Next, I drilled a hole on the side of an extra, generic basket I had and I inserted the thermocouple and added some sealant to ensure the probe doesn’t move and the water doesn’t leak from the hole
Before I use the thermocouple thermometer, I decided to test it against my Bonavita kettle and see if it reads the same temp as the kettle, and it did.
Next, I had to come up with a way to restrict the flow of the water as to imitate a true extraction. For this I used a Rancilio rubber backflush disk that I had laying around from my Silvia days and placed a small hole in it to restrict the flow instead of completely eliminating the flow.
Finally, I was ready for business. I experimented with different cooling flushes but here’s what I settled on:
If machine has been idle for more than 10 minutes (at 1.4 to 1.3 bars of pressure), when you press the brew button you should see a lot steam (approximately 30gm of water) coming out of the grouphead, once that’s done, keep the water running till you hit 85gm then lock the portafilter and pull the shot. The shot will start at 200F or so and will drop down to 198F and will stay there (see video below)
If machine has been idle for less than 5 or 10 minutes, you should get less steam (approximately 16gm of water) out of the grouphead. If that’s the case, simply run the water for an additional 3 seconds after the steam stops for a total of 50 or 60gm of water. This should maintain the same range of 200F and dropping to 198F or 197F.
If you have any questions, let me know in the comments below.
Since I became passionate about coffee and espresso, I always read on the forums and elsewhere that consistency is key. I realized that people are spending thousands of dollars on heavy duty, highly respected equipment to achieve temperature consistency (among other things). Many coffee and espresso aficionados have opted for dual boiler espresso machines with PID so that they can ensure the temperature is consistent shot after shot.
Heat Exchange machines, which uses one boiler with a tube running through it, allow the user to also brew and steam, just like the dual boiler machines but involves a “cooling flush” routine to bring down the temperature to a brewing temperature range (195 to 205 degrees Fahrenheit) by running water from the grouphead. To ensure consistent shots from a Heat Exchange machine the user must be able to run the same amount of water after the hissing and sputtering from the water stops. This can be tricky at times, especially if the user is pulling one shot after another, in such cases the water coming out of the grouphead won’t sputter or flash boil and it will simply be hot. Under those circumstances it’s difficult for the user to determine the brew temperature. This perceived downside of Heat Exchange machines is mitigated with PID dual boiler machines as it eliminate any guess work, counting time or weighing the water coming out of the grouphead during the cooling flush.
This brings me to the topic of this post, is temperature consistency really that important for home espresso? Is it worth the extra money spent on dual boiler machines? My answer and personal opinion is a no! Before I dive deeper into this and present my argument as to why I don’t think that temperature consistency may not be that important, I’d like to make it known that plenty of people, after spending some time with their Heat Exchange machines have developed a solid routine and can produce very consistent results. Also, I’m planning on replacing my Nuova Simonelli Musica (Heat Exchange machine) with a dual boiler some time in the future. I won’t be replacing my Heat Exchange machine neither because I believe the Dual boiler machines to be superior not because I believe in the importance of temperature consistency for the home Barista but because I had a single boiler machine (Silvia) and now a Heat Exchange and I simply would like to experience a dual boiler machine in the future.
Why do I think temperature consistency is overrated for home Baristas? Simply because I’m not sure that brewing at a temperature of 200 vs 204 degrees will yield an incredibly different result! Also, assuming there is a slight difference in taste, I’m not sure that the average espresso drinker at home has the developed, sophisticated tasting buds to be able to notice the difference. Finally, assuming they can notice the taste difference of a 4 degree brewing temperature variance, I don’t think that different is exclusively bad or horrible. This was confirmed to me when last week I pulled a shot just 20 mns after I turned on my machine and the result was a different shot from what I’m usually used to (more acidic with less chocolate notes). However, I still enjoyed that shot very much!
Have you ever tasted espresso from one cafe and liked it and tasted espresso from another cafe and also liked it? It’s pretty much the same experience at home if you get a shot every now and then that’s not brewed at your ideal temperature. Many home baristas and coffee addicts love to visit cafes to experience different coffees and espresso recipes so why not experience that at home (again, assuming you can tell the difference in taste between two espresso shots pulled at different temperatures, all other factors equal).