What about ROK?

Q&A
1

Hi, first post here :wink: iā€™am live in Paris, look like i just found a place where people like me love to get Inside theory to get better result in cup :wink:

i just do a search about ROK machine and found only 1 post without any replyā€¦

How do you consider ROK machine here ? did you tested it ? i use it since 2 months hard at the begining (i never used any Espresso machine beforeā€¦) but when you get it seriously (Eureka Mignon grinder, Bonavita variable kettle
, just ordered a Brewista Smart Scale to replace my eletronic scale Joe Frex bw 500ā€¦, Tamper 51 Joe Frex & hand made Tamper 49,7 to fit right below the mark inside basket) and can get Great result believe me !!

Stephane

2

Hi Stephane,

Hopefully, we can get Matt or someone else interested enough to ā€œscience the s**t out of itā€!

One of my questions is if i have an espresso grind, tamp it with 30+ lbs of pressure, and I can press through an espresso at 1:2 or 1:2.5 ratio at the 30second markā€¦ then the flow rate is no different than a full espresso machine? If so, then the manual control could be used to explore prefusion/variable pressure questions throughout.

With the right grind and coffee, I can generate good crema with an espresso that is better than most 3rd wave cafes. If so, then think what someone who is a professional can do?

Btw, absolutely required is pouring water off the boil into the water chamber and releasing within 10 seconds to the coffee. Plus preheating the water chamber and portafilter if possible. I checked the temperature of the water chamber and anything else leaves the water temp too cold.

Anyway, I am waiting on my refurbishment kit for the Rok so canā€™t explore any further till then.,

3

Hi, i have same question as you :wink:

With one coffee bean i was able to have (while the coffe was running on the cup at 15 sec of the extraction) 2/3 of my ristretto cup full of Crema !! then 5/6 mm of crema at the endā€¦ thatā€™s too much, i had to use a spoon before drink it to remove some crema :wink:

I think problem about ROK is that in some forum they donā€™t talk much about it because of that :

No suitable for Pro use (even if iā€™ve heard that a Coffe Shop just open with Only ROK machine, i forgot whereā€¦)

More complicate then a machine : You control Everything ! the pressureā€¦, possible loose of temperature on the machine (you have to fix that with a little hotter water (or/and like you said preheating the water chamber) etcā€¦

The smaller size of the portafilter : for me This is a point to solve on a future version of ROK, i dream of a ROK 2 compatible with a normal portafilter 58mm, then a bigger water chamber and bigger arms (ot better a Lever !!! :sunglasses: )

We just begin to explore with ROK and thatā€™s great and exciting !

4

I equate the ROK with the Handpresso due the many nuances of brewing a cup. (dependancy on higher temps due to sudden losses of temp; reduced operating pressure compared to a pump-driven machine; and the ability to make a darn fine cup compared to local commercial bars)

Since many different brewing methods have made their way to the bar (aeropress, pour over, cold brew/drip) over the past few years, itā€™s quite possible that the ROK make an appearance. But it would only be a ā€œguest appearanceā€ as it, ultimately, competes with a product that still outperforms it. (a proper espresso) And given the recent tweaks some bars are making with lowering brew temp, brew pressure, and coarsening the grind (something that a few of us pre-third wavers were playing with in the late nineties here in the US), itā€™s possible that ROK is redundant. IOW, a bar can pull a shot that may almost perfectly match the cup characteristics of the ROK (or a handpresso for that matter).

5

After installing the refresh kit for the Rok, very pleased with the results.

30s, 32g of espresso with 15.8 grams of coffee into portafilter and tamped. Timer starts at full release of water.

Baratza Preciso at 8A setting. Really, awesome.

Klatch ā€œWorldā€™s Best Espressoā€ coffee beans.

Until the refresh kit, could not hit these timings.

Still not Klatch or Stumptown level of espresso, but does beat everyone else.

Interesting about the performance of machines to vary pressure parameters, but what those machines will not do is vary the pressure during the shot being pulled which the Rok will allow someone to do. Maybe someone will find something interesting that is not based on a static pressure level.

6

Tottaly agree, should be very interested too :wink:

7

Iā€™ve had a Rok for a while now and can attest to the great results it can produce.

However Iā€™d be wary of comparing the quality of an espresso based on the amount of crema produced.

I find the best results come from long 1:3 type extractions since the pressure required to get a good extraction is less.

As far as exploring pressure profiles on a Rok the issue lies with repeatability. How can you guarantee that youā€™re applying the same pressure at the same points in the extraction on such a simple system.

Also FWIW there are plenty of commercial machines with the ability to change pressure during the shot. And most processionals that have tried to experiment with the exact details of pressure profiling have had difficulty actually quantifying and qualifying any results.

8

So after further experimentation, new results :slight_smile:

I am now at 1:2-2.5 extractions with similar taste profile to Stumptown standard espresso ā€œHair Benderā€.

Pressure does not seem to be an issue, however to manage timing of a 28s shot with dose of 17.5g and the 35g and 42g yield is very dependent on ā€œoverdosingā€ the portafilter beyond the standard.

Also when tamping, an initial light tamp to make sure all the grinds are in the portafilter, tap around the edges, smooth again, tap again, and then press down. This should have the compressed grinds right at the inner line inside of the portafilter.

Without overdosing the portafilter, canā€™t get decent extractions unless going long 1:3+.

Soā€¦

Use scale under espresso cup. Pre-heat portafilter and water chamber. Water on the boil pour into chamber and immediatelyā€¦

Lift up on handles, once water drops completely start timer, immediately press down until resistance felt, raise handle back to top.

At 6seconds press quickly and firmly keeping full pressure watching weight and timer, only vary pressure middle and toward the end if necessary to hit volume and timing window. Better to run shot a little early than 28s than lighten up pressure too much.

Good crema during this process, probably 75% of what you get at Stumptown.

Anyways, thatā€™s how I manage it.

9

I think the most overlooked thing about ROK is the temperature problem. The pressure is the most obvious one to come to mind, but I think temperature affects the beverage more dramatically.

The water chamber is very little, and thereā€™s no way to heat up the whole device easily; so you either waste a lot of water and effort to heat it up, or you brew with a water temperature that is sub-optimal for espresso brewing. And even if you heat it up successfully, thereā€™s the problem of keeping the temperature (and more importantly total heat of the device) stable, which I wonā€™t get into.

Overall, with good soluble roasts and a bit of effort, I think drinkable beverages can be produced; but in places like here (Turkey) where you really canā€™t find very soluble roasts, itā€™s more like a useless novelty.

10

Just to further update, after the step of ā€œimmediately press downā€ then prime the pump with 3 short pumps which increases pressure. This one change allowed much more crema to be developed with actual tiger striping.

Found another video on youtube where this technique was used and coincidentally (likely best practice), 17.5 grams of coffee was also used.

Timing was perfect for 25-28 seconds at 1:2 ratio.

11

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.
Press:
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 ā€œresistanceā€, 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 ā€œtampā€ the coffee itself. If not tamped hard, channeling and rate of water flow is too fast and not repeatable.

Soā€¦ 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 ā€œthingā€. :smiley: