The final recipe for posterity sake, though website is in effect, shutdown.
This has been tested with a bottomless portafilter, absolutely zero errant drips, two streams that join less than 5 seconds with expected tiger striping. Bottomless portafilter is absolutely REQUIRED to test. Once this was done, the included portafilter with spout reproduced the same results as the bottomless.
Many shot pulls of experimentation to solve the channeling problem, but is done now.
Coffee: Stumptown HairBender - 7 days off roast
Dose: 17.0g (level basket) (ratio 1:2.1)
Grind: 3 exactly, on Lido 3 hand grinder
Tamp: 49mm tamp flat, dosing funnel. Fill. One vertical tap on counter, and then several horizontal taps. WDT with chopstick and paperclip straightened out, then North, South, East, West level with a hario bamboo wood stick. Tamp straight down(till complete resistance, so hard), nutate, straight down again, polish. Wipe loose grinds from top bevel, turn upside down to remove further lose grinds.
Preheat portafilter in cup of hot water. Preheat Rok chamber. Insert portafilter. Place weight scale (using Hario) with espresso cup.
Fill chamber within a half inch of top with boiling water, immediately release the water by raising arms as fast as possible without spilling over the chamber.
Once water is released immediately press down to “resistance”, raise arms and immediately start timer, then perform 4 pumps to slight resistance and start to press down at 7s till there is firm resistance. Maintain same level of firm resistance until 35g and then let up on arms. Should be around 30s at this time, better to go slightly longer in time than shorter with the Rok. Unless making cappucinos, brightness to stand up to the milk is good. Hint: timer on seconds will become roughly the same as amount of shot being pulled in grams.
If over 32s, grind coarser (Lido 3.1), if under 30s grind finer (Lido 2.9). Very small increments make a large difference.
Keep in mind, that depending on coffee the dose amount may vary a great deal so can be anywhere from 15.5g to 18g. The important point is that grinds must be level at the bevel, and then tamp down to the inner ring.
The silicon spray head, must not come in contact with grinds on insertion into portafilter so tamping to the inner ring is critical to eliminate channeling.
A hard tamp is required, since the pressure inside a Rok does not “tamp” the coffee itself. If not tamped hard, channeling and rate of water flow is too fast and not repeatable.
So… pulling espresso shots with the Rok has been solved. Completely. This is thanks to the many countless videos on youtube, stealing ideas from everyone and everywhere. I haz no shame. I haz really good espresso.
In honor of Rok being from the UK, and for various other reasons, the above is now officially noted as the Lambethian Technique. Once something is labeled, it becomes a “thing”.