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.