Hi all, after being a long lurker here I've finally decided to sign up to ask for advice!

I recently wound up with a Rok GC as my first espresso-type machine, and have been having I would say moderate success so far. Hoping some folks here may have tips.

Grinder is an older Baratza Virtuoso - not fancy, I know. I've been grinding around a 6 on that so far (started at 8 but found that wasn't fine enough). I did pick up a 49mm tamper - slightly undersized, but was having trouble finding a 49.7.

Workflow has been to boil the kettle, run two shots through the assembled group with no grinds. Then dose, assemble, pre-infuse, and pull.

First few attempts with one bag were really sour. I did switch to a different roaster today, which made some difference.

My most recent (and most successful) attempt today was 18g of grinds in, ~36g liquid out, ~15 second pre-infusion, I think ~23 second pull. It wasn't *bad*, but still a bit sour, and quite sharp (but it is more of a medium espresso roast, not super dark, so that may be part of it.

I think I've hit the limit of grind fine-ness, but as it is, I don't find it physically hard to pull the shot. I can lengthen the pull time, but it feels like I'd really be applying pretty mild pressure - certainly not forceful pressure, unless I wanted to pull a shot in like 15 seconds.

Any thoughts on my evolving workflow appreciated, but also your anecdotes/tips as well!

Thanks!

Keep going finer.. I am not familiar with that grinder.. but basically you don't have enough puck resistance.. setting on a grinder doesn't mean anything as they are not consistent from one grinder to another. The ROK doesn't have a pressure gauge so it cam be a bit difficult to determine .. but it sounds like you are not near to achieving a high enough pressure for part of the extraction. Your preinfusion could be too long.. If you soak the puck at low pressure too long, it might break up a bit and you'll get channeling for the remainder of the shot (hence the sour).. Maybe aim to add a little pressure for 5-8 seconds then try to ramp up pressure to see if you get more resistance.. then you can tweak the pre-infusion.

I've tried the ROK GC vs the Flair Pro v2 and the Robot, and your espresso will be thinner with the ROK than the other 2.

Thanks! I thought the grind seemed fine enough, but will push it further in the name of experimentation! Can definitely also play with the pre-infusion once the pressure seems a bit better. I *really* wanted a Robot, but the ROK came as a gift, so I want to give as much of an effort to like it as I can.

Hi! I too have a ROK GC - I second the advice to go finer. My grinder is set well finer than one might use otherwise. I have found that 15-16g works better for me.

For anyone curious, after tweaking a bit, this is my current routine (obviously anecdotal).

- On my Baratza Virtuoso, 4 or 5 clicks from finest setting (info on both below).
- 16g dose.
- Let portafilter sit in cup of just-boiled water for ~2 minutes (not sure of any temperatures).
- Run two pulls of just-boiled water through the Rok.
- With the grinder at 5 clicks, 20 second pull.
- With the grinder at 4 clicks, 30 second pull.
- ~42-43g out (I keep meaning to just put less water in to start as well - next time).

Both the above grinds/pull times tasted surprisingly similar using Drumroaster Gold Label (https://www.drumroaster.com/coffees/gold-label-espresso). I'd say the finer/longer one was a bit more acrid. Passable, and would probably be fine in americano or milk drink, but still noticeably sour (but not immediately face-puckering like the first few days of experimentation).

Next steps are to pay more attention to my water volume in so I can get a full pull without hitting a really long shot, and try to find a more "classic" espresso to use. It seems like everyone local is focusing on the lighter side of things (which I don't mind for other brew methods), but I think this machine needs something darker (and I prefer a rich, syrupy espresso), and it's really hard to find something local/fresh like that!

Been continuing to experiment.

Picked up their naked portafilter to see if it would help give any insight. For some reason it seems to be generating a lot more pressure/resistance (and leaking some water), but I do think I'm getting better tasting shots. Extraction seems kind of... uniformly uneven, if the pattern on the filter is anything to go by.

Also have gone to some non-espresso roasts to get something darker. Currently using the West Coast Trail roast from Fernwood (https://fernwoodcoffee.com/collections/ ... dark-blend) and it's pretty tasty. I've actually veered from extremely sour with my previous beans to a little bit too bitter with this one, which is kind of a good sign, since I'm seeing more flavour range.

Overall, still pretty meh on the unit, but seems to be improving a bit.

I tried a unit which also leaked when pressure increased. The vendor said the plastic core parts could be faulty. I returned and got a flair

Where did you find the leaks coming from? As far as I can tell it's somewhere in the PF/body interface on mine, so could be an issue with the PF, not the body.

Was actually a friend's unit.. leaked at same place.. the PF didn't make a good enough seal with the screen..we had unit for 2 days.. I will say that you need to lock the PF much harder than it appears.. so if it leaks.. lock harder and see if that fixes issue. On ours the leaks were less when we used more force, but it still leaked a little and so returned it as a defective unit.. the vendor took it back no questions .. since we lost some faith in the design under full pressure my friend paid extra and went with ProV2 Flair which works very well.. Make sure you have no grounds between PF and screen and lock harder.. (think we had to go 3/4 rather than 1/2) .. likely your leak will stop.. I was worried we might have to go harder and harder until we ran out of turning capability.. My friend was going to go with the Rok grinder, but ended up with a Kinu Phoenix.. very impressive.. that is a nice hand grinder if you are in the market..

Really appreciate the information! I will pay closer attention tomorrow and see what's up.