As anyone that owns an espresso machine knows, getting the grind/dose/temperature right takes a few tries. The first challenge is getting the cooling flush correct. While the Super's group holds at a nice 200F thanks to the thermosyphon restrictor, the heat exchanger still needs to be flushed. One thing I noticed very quickly was how short the flash boil lasted. The Domobar Super only required around 3 seconds to reach the end of the flash boil thanks to the cooler group.
I tried several iterations of the cooling flush, flush and go, flush and recover, short flush short recovery short flush and go. Even with the larger boiler, the Vibiemme required some recovery time according to my taste tests. My boiler is set at 1.1 bar at the top of cycle. I learned very quickly that the Domobar Super requires a very short shot cooling flush at the start of a session. If you are fast enough on the grind/dose/tamp you can even forgo the flush between a series of extractions.
To test the recovery rate I decided on a flush-less inter-shot test with a two minute rebound between each shot. I went with two minutes because that is a reasonable time for a home barista to knock out a spent puck and prepare the next shot. As I said, I did away with flushing between shots and simply pulled a 2oz sample. I let the machine idle for an hour and a half to make sure everything was at operating temperature.
Each shot ran 39 seconds, a second to start the stopwatch and datalog on the Fluke then flip the lever up, one second between flip the lever down and hit datalog and stopwatch stop. I ran five back to back tests. I could almost key in the data once and then copy past it into another column for the graph. The temperatures were within a few tenths of a degree every time. All readings were taken using one of Eric's grouphead mounted thermocouples and a Fluke 54-II datalogging thermometer.
The five tests yielded some very surprising numbers, the ending temperatures were as follows (°F):
- Series 1 202.3
- Series 2 202.3
- Series 3 202.3
- Series 4 202.3
- Series 5 202.3
If those are not repeatable results, I don't know what is. Shortly after that test, my Scace II thermofilter arrived. So as a point of due diligence I repeated the test using both Eric's adapter and the Scace II.