I own a La cimbali m21, So far I got my grind right and dose right (room for improvement). I roast my own beans at a Vienna Roast and let them air-out 2 days before use. It looks like my shots are blonding about 1 1/2 oz in, using a 20g double filter. I have tried many different techniques to prevent the early blonding. Also with any bean I have tried I get super mega crema, almost too much crema. Always very bitter or sour tasting. Does this all sound like too high pump pressure? My boiler is set to .9 bar and i give it a flush to rid of the super heated water before pulling a shot. Any suggestions will be much appreciated :)
Adjusting the pump will not affect the steam boiler pressure you are reading. Correct steam boiler pressure is 1.1-1.3BAR. Correct pump pressure is 8.5-9BAR. Do not trust the gauge (if you have a dual mano gauge and it sounds like you don't) you have to use a portafilter and install a pressure gauge on the threaded spout on the bottom. You should be able to find the proper gauge and adapters at a specialty hydraulics shop, or an online vendor. Adjust pump pressure while it is running.
+1. OP, your beans should typically rest 6-10 days, occasionally less or more, depending on the bean and roast. Ideally, they should rest in the foil bags with release valves that good coffee roasters use. Alternatively, in freezer bags that you open and reseal occasionally during the resting period (they'll often puff up with CO2 being released).
The "super mega crema" you're seeing is probably a lot more foamy than it should be... it collapses very quickly, yes? You can hear it collapsing, like foam on a warm soda pop poured quickly into a glass. It's actually caused by the same thing - excessive CO2 agitated from the beans.
Not only does proper resting allow roasted beans to de-gas but it allows their flavor to settle and develop too. Caramelized sugar and other flavors lose their sharp edges and often develop new flavor notes you won't get if using the beans too soon.
Finally, the CO2 erupting from unrested beans during the pull helps in over-extracting. Caffeine and other bitter stuff gets higher in the flavor profile.
So, "super mega crema" and "bitter" are probably cured by bean resting. "Sour"? Might be something that resting will also cure as flavors settle, or could be a result of too-low temperature during the pull ("bitter" could also be a result of too-hot).
Plus a couple of other things... It's possible -- more than possible really -- that you're not temping right. I don't know if if you could taste the bitterness which comes from brewing too hot though the bitterness and in your face aggressiveness which comes from using beans with insufficient rest... but you're almost certainly brewing too hot.
TEMPING AN M21 Temping an M21 after warmup or a long idle is a too stage process. First you have to stabilize the group with one pull. Then, you can temp the brew water.
Warm up requires about forty minutes. The Junior group, once stabilized, is extremely stable and won't require much in the way of further stabilization unless left to idle for longer than hour. The way to atabilize it is to allow it to overheat, pull sufficient water through it so the HX water is cooler than the group and cools it a bit too much, then allow its connection to the boiler a couple of mintues or so, so the entire group mass (and it's massive alright), comes to equlibriation.
Sounds complicated, but it's easy. The first time you approach the machine for the day after warmup, or if it's been left to idle for more than hour, pull a lot of water -- at least 6 ounces -- through the group and an empty pf. Allow the group to rest for at least three minutes.
I suggest programming one of the buttons (I use the double-double on the far right) for an 8oz temp-the-group pull; but I'm conservative in that respect. I also suggest waiting at least five minutes before pulling your first shot; but I'm impatient, never do; and instead use the sacrificial grinds from purging the grinder to pull an initial stabilizing shot after allowing the machine just long enough for the water in the HX to superheat (flash boil) -- a minute, maybe.
Then and only then, after the group is stabilized, load and prep your basket as usual, temp as usual and pull your first shot of the day.
Temping as usual means temping the brew water only, not the group. If the machine has been idling for more than a couple of minutes, the water in the HX will be superheated, and will "flash boil." That's a good thing -- especially as you get used to the machine -- because it provides a baseline.
With the pf prepped and ready to go -- but OUT of the machine -- pull water through the group (using the free pour button) until flash boiling ends. That's your baseline. Then, to accurately temp, pull again, anywhere from a "3" count to an "8" count of water through an empty group to temp the HX water. As my internal clock counts, 3 is on the hot side of the range (204ish), and 8 is on the cool (197ish). I start with about 4sec (200ish) and dial-in by taste (balanced bitters and sours) from there.
Once the group is stabilized, the Junior recovers EXTREMELY QUICKLY. If you're pulling successive shots quickly enough that you don't get flash boiling, BUT you use at least a short flush to clean the crud off the screen between shots (you definitely SHOULD), figure a 3sec cooling flush before locking the pf in.
Once temped, the Junior is one of the easiest and most forgiving espresso machines at any price. The only HXs which compare are other Cimbalis using the same group, or the NS Aurelia. In terms of stability and overall ease of temping, it's the ultimate "Agnostic," and might as well be a DBPID.
SHOT VOLUME: Forget volume. Start measuring output by weight. Volume means nothing. Your machine is pulling "near gushers."
GRIND AND DOSE: If you're dosing 18g into an 18g basket you're either dosing correctly or you're damn close. However, whether or not your grind is right is determined by flow and taste.
If you get 33 - 37g output to the blond point from an 18g dose, in 22sec - 30sec, your flow rate is very close to "right" for a normale. But taste is the final arbiter. If your flow rate is too fast or too slow and you get good mouthfeel, a lot of sweetness, and balanced bitter-sour... Then who cares about the flow rate?
Pardon me for being so blunt, but it saves time and is unambiguous... Given your results so far, you don't seem to have a good enough handle on what's going on to know whether your grind is "close" or not. When you say it's "close," you're guessing. You want to move from guessing as soon as possible into the realm where knowing what's going on meets doing things on purpose. The good news is that you'll get there pretty quickly.
PREP Unless your M21 is a Casa, the lack of pre-infusion means that prepping a basket requires nearly perfect technique. If you're not using a crotchless pf, start. Unless you're using an uber grinder of some sort, AND get very little in the way of meaningful clumping, you'll probably have to resort to WDT. Light or firm tamp doesn't matter much, as long as your pucks are perfectly consolidated and tamped perfectly level.
The one ray of sunshine in all this PITA prep, is that a bottomless pf will give you better mouthfeel. And set aside the "triple" basket which comes with the naked pf. Use a standard, double size. I suggest a ridged, 18g VST or (same basket) ridged 17g Strada.
GRINDER GRINDER GRINDER While an M21 is ruthless about revealing the flaws in your prep technique, it will bring out the best from a grinder. That sounds like good news, but every silver lining has a stormy cloud. That is, it will bring out a lot more good from a lot more good grinder than one which is (cough) merely acceptable. As a practical matter, the LSM 92/Mini/Vario class is at the very bottom of acceptable. Start saving.
By way of example, when using my M21 to compare the excellent in the cup but pain in the ass to maintain Titan class La Cimbali Junior Max to the uber-Titan conical Ceado E92...
Dude! The superiority of the Ceado in the cup was astounding. Forget the particular identities of the grinders. That says something important about the resolving power of the M21.
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