The Vibiemme also comes with a single basket and will produce a very good single espresso. In this country, the emphasis tends to be on double espresso and the diminutive single gets overlooked. That's a shame. To encourage you to give them a try, this section describes the steps towards preparing a satisfying single espresso.
The end goal is a one ounce drink produced in around 28 seconds. The diminished dose of a single requires a finer grind, so an adjustment on the grinder is needed. But before you can adjust the grind, you must determine the optimal starting dose. One of the critical points is to get the proper headspace (the air space between the top of the puck and shower screen). If you overdose a single, you may not be able to lock the portafilter into the group or the surface of the puck will scrape against the shower screen. That will crack and disturb the puck, leading to channeling.
One trick to gauge the dose starting point is to use a nickel as a gauge. Dose into the basket and tamp, then place a nickel on the surface of the puck, and then lock the portafilter into the group. Next, remove the portafilter and look at the puck. If the nickel is pushed deeply into the puck's surface, or there is any cracking of the puck, the dose is too high.
The following pictures demonstrate this process. I started off with a 10 gram dose in the stock single basket and distributed the dose by tapping my finger against the side of the basket. I also tap the basket down against the tamping stand to further level and settle the dose. Finally, tamp, place the nickel on the center of the puck, lock it in, remove.
As you can see, the dose is too large. The shower screen did not make contact with the puck, but the nickel was pressed deeply into the puck's surface, causing radial cracks in its surface.
First test at 10 grams (L) and second test at 9 grams (R)
Using the results from the 10 gram test, I dosed down to 9 grams for the second try. Once again I prepared the dose and placed the nickel in the center of the pucks surface and locked in the portafilter. This time the nickel was slightly indented in the surface of the puck. Nine grams is thus the starting point.
I continued to down dose without the nickel in 0.5 gram increments. At 8 grams, the tamper was bottoming out against the concave sides of the basket. I was still getting a level puck, but it was not fully compacted by the tamp. You will feel when the tamper is hitting the basket instead of being stopped by the puck. I decided on a 9 gram dose for the Caffe Fresco Ambrosia blend. An 8.5 gram dose would also work but I was very, very close to bottoming out the tamper. You could also do like the Italians and grind extra fine and use a very light tamp just to level the puck.
I find the single shots from the Domobar Super to be comparable with other E61 vibratory pump machines. The singles tasted a little sweeter and brighter than the doubles with a creamier mouthfeel. So who says bigger is always better? A good single espresso is well worth the work.