Sherman Chong and Jim Schulman broke off an experiment to confirm a consistent difference in the taste of paired shots, one ground with a hopper, the other single dose, when it became clear that there was no discernible taste difference, consistent or otherwise, between them.
We tested a Compak WBC using a blend of Brazilian, Guatemalan, and Kenyan coffees at various roast levels, and a Mazzer Super Jolly with a Vienna Roasted Sulawesi. The grinders were set to produce the same 1.5 ounce volume, in the same 30 second shot time, at the same 15.5 gram dose, in the same Faema style baskets. The grind setting was adjusted to achieve this for both grinders alternatively equipped with small, full hoppers, or with 16 gram single doses in the throat, weighed down with a tamper.
About 15 to 20 grams of purge coffee was ground between grinder changeovers. Grinders were changed over every two shots, In other words, the first round was hopper grinding first, then single dose, the second round, single dose first, then hopper grinding, etc.
The baskets were unobtrusively marked. The person grinding flipped a coin to determine which basket went with which grind option. Then the person pulling the shots shuffled the baskets. So by the time the shots were pulled, neither person knew which coffee was which. Both testers tasted each round.
The shots were pulled on a pair of Elektra Semi-Automaticas at the same time. The shots were preceeeded first by a cooling flush, then a single pulled a minute earlier, and then a cleaning flush, in order to settle the machines into their optimum performance.
There is a slight difference in the pump performance of the two Elektras, so that the shots layer differently, and the crema alone on one machine tastes stronger than on the other. The difference completely disappears once the shots are swirled and rested for 15 seconds. This is what we did when tasting.
Once each grinder was properly calibrated, the plan was to pull four rounds of shot pairs per grinder. The first two rounds were to familiarize oneself to with taste differences. The final two rounds were to be used to attempt the correct identification of the coffees. A perfect record by one taster for both grinders, or on one grinder by both tasters, or seven out of eight correct guesses pooled over both tasters and grinders would have been a significant result. Six out of eight pooled would have been somewhat suggestive; but not a significant result.
In the first two rounds of both grinders, neither Sherman Chong nor Jim Schulman could in any way distinguish the shots. "They could have come from the same cup," Sherman remarked. Since we could not taste a difference, there was no point in going on to test whether the differences we had tasted were real. We abandoned the tests on both grinders after two rounds a piece.
As usual, the best information came from the surroundings, not the test itself.
It was extraordinarily difficult to dial in the grinders, especially the SJ. It took me three tries to dial in on the Compak, and it took Sherman five on the SJ. When the grind settings drifted apart, getting them synchronized again was not to be done with linearly proportional adjustments. On the Compak, I noticed no difference in the degree of finickiness in adjusting hopper and single shot grinding, but I did notice they were different. Sherman had slightly harder time setting up the single dose.
I speculated previously that single dose grinding may turn out to be more finicky. I don't think the set up problems we had setting up bore this out in any convincing way. What they did bear out is this:
- Keeping the grind dialed in correctly works differently when doing single dose and when doing hopper based shots.