Flow Control and Pressure Profiling for E61 Machines

Espresso flow control on an E61 is a variable orifice in the brew path—usually a needle valve or a paddle—that meters how fast water enters the group while the pump runs. Pressure profiling is the pressure shape that follows: a slower climb, a held lower plateau, or a falling tail. The control sets flow. The coffee puck and the over-pressure valve decide the bars you actually see. A stock E61 already softens the opening seconds with a mechanical chamber. A kit earns its complexity only after open-valve shots are repeatable and you want a longer soft start, or a shaped ramp, that you can taste in the cup.

This Kairos Coffee page stays on that decision. The group’s own lever, cam, and pre-infusion chamber are covered in E61 group head explained. Why a low-pressure soak helps a dense bed is covered in espresso pre-infusion explained. Pump ratings, brew pressure, and the OPV live in espresso pressure explained. Thermal differences versus a saturated group are in E61 vs saturated group head. When you are ready to look at hardware, start from coffee machines.

Quick answer:

• What you turn: an orifice (needle or paddle), while the brew lever still starts and stops the shot on a typical install
• What changes: millilitres per second into the group, so the pressure rise slows, stretches, or drops
• What it cannot set: a saved “6 bar then 9 bar” program the way an electronic profiler can
• Highest-value use: one marked soft start, then full open, on a puck you already prep well
• Skip it when: yield time still wanders with the valve wide open, you have no group gauge, or the group is not an E61

Who This Guide Is For (and Who Should Skip It)

Who it’s for: you already own a standard E61—heat exchanger or E61 dual boiler—and your open-valve shots land on a stable dose, yield, and time. You pull denser light roasts that still channel or taste sharp in the first sip after distribution, WDT, and a sane grind change. You are choosing between a needle-valve kit and a paddle kit, or between adding a valve to this group and buying a different machine that stores a profile. You like logging a few shots and you will fit a group pressure gauge, because a knob without a group reading is a guess.

Who should skip: stop here if any of these describe your week.

• The baseline still moves. With the valve fully open (or with no kit at all), shot time for the same dose and yield swings by several seconds every morning. That swing is grind, distribution, basket, or temperature. A second orifice adds a swing you cannot assign.
• You are still learning the first recipe. A workable home target is a familiar double—often 16–20 g in, about twice that out, finishing in a rough 25–35 second band including the stock E61 soft start. Hit that band for a week before you shape anything.
• There is no group pressure gauge and you will not add one. The round gauge on many heat-exchanger panels reads the steam boiler or the pump circuit. Flow control is judged at the group. Our pressure gauge guide shows which dial is which.
• The group is saturated, ring-heated, or a super-automatic brew group. E61 needle and paddle kits are cut for the E61 top works. They are the wrong part on a saturated group. Read E61 vs saturated group head before you order metal.
• Service speed matters more than a shaped shot. A busy bar that must repeat a drink in a short window should leave the path fully open or use a machine with a saved profile. Hand-moving a valve mid-ticket is a hobby workflow.
• You already like the cup. A new restriction will not make a balanced medium-dark shot more “advanced.” It will make the next ten shots less familiar until you relearn them.
• You want the machine to hit bar targets by itself. That feature is electronic pressure profiling. A paddle you must move is a different purchase.

Use this: if the skip list fits, spend the money on a better grinder setup, a scale, and calm puck prep. If you cleared the list, the rest of this page is the buying and dialing map.

What Espresso Flow Control Changes on an E61

A classic E61 brew lever is a cam. Fully up, it opens the inlet and, on a pump machine, starts the pump. Fully down, it closes the inlet and opens the exhaust so pressure dumps to the tray. Many machines also have a middle lever position used for line-pressure wetting when the machine is plumbed in. All of that stays true after a typical flow-control install. The kit does not replace the lever. It adds a second restriction in the water path into the group, usually at the top of the group where a cap or mushroom sits.

Stock behavior is already a short, passive soft phase. A spring and a lower chamber delay the climb toward full brew pressure for a few seconds. The mechanism, the three lever positions, and the thermosyphon are the subject of E61 group head explained. Treat that page as the anatomy lesson. Here, remember one consequence: the chamber can only fill as fast as water arrives. A tighter inlet stretches that fill. That stretch is the first thing owners feel when they crack a needle almost closed and raise the lever.

Three jobs get confused in product titles:

• Flow control is the orifice you set. Smaller opening, fewer millilitres per second, for the same pressure difference across the valve.
• A pressure shape is what the group gauge does over the shot because of that flow, the puck, and the OPV. People call the whole habit pressure profiling.
• Electronic pressure profiling is a pump or gear system that follows a saved bar target over time. You are not holding a handle. An E61 needle does not become that system because the knob has numbers printed near it.

So “pressure profiling” on a manual E61 is an honest nickname for a hand-made pressure shape. The hardware you bought is a flow restrictor. If a listing promises “set 6 bar,” ask where the machine measures and whether anything holds that number when puck resistance changes. On a needle kit, nothing holds it. You watch the group gauge and you move the handle.

Use this: buy the kit as a way to slow and shape inlet flow on an E61 you already understand. Buy a different machine if the feature you want is a profile that repeats while your hands are on the steam pitcher.

Needle Valve vs Paddle

Needle and paddle are two handles on the same idea. A needle valve is a tapered pin moving in a seat. A small turn near closed changes the open area a lot; the same angular turn near fully open changes flow less. A paddle is a lever that sweeps a valve through an arc. On many kits the paddle simply rotates a needle or a rotary valve. The water does not care what your hand holds. Your repeatability does.

Choose the handle you will return to the same place while a shot is running and a scale is ticking. That is the whole comparison.

Those dollar bands are planning ranges home owners commonly see for the valve hardware alone. Street prices move, gauges are extra, and a shop install is extra again. Use them to compare against “buy a different machine,” not to rank kits.

Which handle to buy

Buy a needle knob if you dial at the counter, you will mark two positions (soft and full), and you expect to leave the soft mark alone for days. The knob rewards patience and punishes fiddling. It is the better default for a first kit if your goal is a longer pre-infusion and then a normal brew, which is the use that pays off most often.

Buy a paddle if you already know you want staged gestures and you will practice them until the sweep is boring. The paddle is easier to open at the moment drops appear, and easier to ease back at the end of a shot. It is a worse first kit if you treat the middle of the arc as a precision setting and never mark it. Unmarked middle positions drift with your mood.

Skip both if you intend to steam milk and “play the profile” on the same shot before the open-valve recipe is dull. One new variable is enough. Milk texture is already a variable. Add the valve on days you pull espresso only, until the marks are habit.

Install reality belongs in the decision too. A kit that bolts into a standard E61 top, reuses the cam geometry, and comes with gaskets is a Saturday job for someone comfortable opening the group. A kit whose sheet says “machine the group” or “drill” is a machinist job. Photograph every spring and gasket before you lift the cap. After assembly, run water through an empty basket and confirm two things: the cap does not weep, and the lever-down position still exhausts into the tray. A pretty paddle that traps pressure in the portafilter is a failed install, whatever the coffee tastes like.

Use this: needle for marked, mostly-still settings; paddle for practiced sweeps. If you cannot describe the two or three positions you will actually use, you are not ready to choose metal.

How Restricting Flow Changes the Pressure Curve

There is no universal E61 pressure curve to copy, and this page will not invent one. Group pressure is a result, and it moves when the puck moves. What follows is the hydraulic pattern you can expect, then check on your own group gauge. Times are home working bands, not a laboratory trace.

Picture two resistances in one stream. The valve opening is the first. The coffee bed is the second. The pump supplies the stream. The OPV limits how high pressure is allowed to rise on the pump side of the circuit—the reason a “15 bar” pump still brews near a classic ~9 bar class when the path is open and the puck resists. That limit is explained in espresso pressure explained and in OPV adjustment. Flow control does not replace the OPV. It adds a drop upstream of the puck.

What a wide-open valve does

Wide open, the extra orifice is large enough that it barely matters. The shot resembles the stock E61: a short mechanical soft phase while the chamber and the top of the puck wet, then a climb toward the machine’s normal brew plateau if the bed resists, then a hold while you reach your yield. Your group gauge, if you have one, is the picture. The panel gauge may already be sitting near the OPV setting while the group is still in that soft phase. That mismatch is normal. It is also why people “profile” the wrong dial and think the kit is broken.

What a tighter opening does

Close the orifice partway and fewer millilitres per second get into the group. Four observations follow. They show up together; they are one mechanism.

• The rise takes longer. The chamber and the puck fill more slowly, so the soft phase stretches past the stock few seconds. A useful home hold is often on the order of 5–15 seconds until the basket is wet and drops are steady, then you open. Past that, you are choosing a very long soak on purpose.
• Group pressure can sit below the normal plateau. The pump side may already be at the OPV relief pressure, with excess water bypassing, while the group is still climbing or parked lower. The missing pressure was spent pushing water through the small hole. You did not “set 6 bar.” You created a pressure difference, and the group reading is what remains downstream.
• Opening mid-shot lets the group catch up. As the hole gets larger, the drop across the valve shrinks. If the puck still resists, group pressure climbs toward the same plateau you see with the valve wide open. That climb is the ramp people want from pressure profiling on an E61.
• A coarse or channeled bed refuses the story. Water that finds an easy path leaves through the spouts. Group pressure stays low no matter how confidently you hold a “profile angle.” The valve cannot invent resistance the puck does not have. Fix the bed first; espresso channeling is the checklist.

A falling tail

Ease the valve toward closed late in the shot and flow falls. Group pressure usually falls with it. Baristas try this when a light roast blondes early and the finish is harsh, hoping a declining tail softens the end. Sometimes the cup agrees. Sometimes the shot was already balanced and the late close only starves the end, leaving a hollow, sour cup. Taste a paired comparison: one shot full-open after the soak, one shot with a slight close in the last few seconds, same dose and same yield target. Keep the close only if you can taste it twice. A declining tail is a full-profile move. It is not required for pre-infusion, and it is not a default for every light roast.

Fully closed is not a profile step

A needle slammed shut while the pump runs is a dead-head. The OPV should bypass and protect the circuit, the pump gets noisy, and the group learns nothing about the coffee. Do not hold that state. Crack the valve until you see a slow wet on the basket or a slow movement on the group gauge. If your machine has no reliable bypass, or you are unsure, keep the pump off until the orifice is open enough to flow. Confirm OPV behavior on the gauge guide before you make a habit of restricted shots.

Use this: judge the kit by the group gauge and the scale together. A slow pressure climb with no drops means the bed is very tight or the valve is nearly shut. Fast drops with a limp gauge mean the bed is open. Match the orifice to the bed you actually locked in, then change one of them.

Pre-Infusion vs Full Pressure Profiling

Pre-infusion is the opening act: wet the puck gently, then extract. Full pressure profiling is a shape across the whole shot. Owners buy one kit and accidentally attempt the second job every morning. Separate them before you touch the knob.

The reason a soft wet helps—even saturation, fewer early channels on a dense bed—is already laid out in espresso pre-infusion explained, including programmable, manual, and stock E61 versions. Do not rebuild that argument here. The decision on this page is how much of the shot you insist on shaping by hand.

When level 1 is the whole project

Use manual pre-infusion when a dense, light, or very fresh coffee sprays or tastes sharply acidic even though the puck prep is clean and the open-valve shot is merely “almost.” Hold the small opening until the basket darkens evenly and drops are a steady thread—commonly somewhere in a 5–15 second band—then open fully and stop at the same yield you used on the control shot. If the cup gets sweeter or simply less harsh at the same yield, keep the mark. If the cup gets hollow and sour, you soaked too long or the grind was already too coarse; shorten the hold before you grind finer and choke the puck.

Traditional medium-dark espresso blends often want less of this, not more. They flow readily. A long trickle can rinse out the body you bought the coffee for. If the open-valve shot is already sweet and heavy, leave the valve open and spend your attention on the steam pitcher.

When level 2 is justified

Move to a full manual profile only after three conditions are true at once. Level 1 is repeatable on the same mark. You can taste a difference and you want a further change at the end of the shot, not a new toy. You will pull paired shots—one control, one changed tail—before you declare a winner. A reasonable experiment is a slight close during the last 5 seconds or so, still aiming at the same beverage weight. If you cannot hit the same weight, you changed yield and profile together, and the taste note is worthless.

Stop the experiment when shot time for a normal double, soak included, runs out toward 45–50 seconds and the cup is sour. Open earlier. Also stop if the first 10 seconds already gush blonde: the grind is too coarse or the “small” opening is not small, and a late close will not repair a channel that already happened.

Use this: pre-infusion is a soft start plus a normal brew. Pressure profiling, fully done by hand, is a performance you owe the scale and a notebook. Most home E61 owners should live at level 1 for months. Level 0 remains correct for a blend that is already right.

What to Have in Place Before You Move the Valve

Flow control amplifies whatever the puck and the hot water are already doing. Set the stage so a change in the cup can be blamed on the orifice.

A group reading, not a boiler costume

Fit a gauge that sees group or puck-side brew pressure: a group-body manometer on many kits, or a portafilter gauge used for checks. Typical gauge hardware often sits around $40–120, separate from the valve. Then read it with the method in the pressure gauge guide. During a restricted shot, expect the group needle to lag the pump-side story. If you only own the front-panel gauge, do not pretend it is drawing your profile.

A locked baseline

For three shots with the valve fully open, write down dose, beverage weight, time from lever-up to target weight, and one taste word (sour, balanced, bitter). A common double to freeze is 18 g in and about 36 g out, in that 25–35 second neighborhood, but use the recipe you already trust. The point is freezing it. Basket type stays put. Tamper stays put. If you change coffee, you restart the baseline. Fresh light roasts move for several days after roast; do not judge a new valve on a bag that is still wildly degassing.

Heat-exchanger flushes need a second look

On an HX E61, a cooling flush is how you stop the first shot from running too hot. A long restricted pre-infusion pulls water through the heat exchanger more slowly than your old flush-and-go habit. The temperature you land on can shift even though you “did the same flush.” After you add a 10-second trickle, pull the flush test again: too hot tastes sharp and bitter, too cool tastes flat and sour, and neither of those is the needle’s personality. The flush routine itself is in the E61 cooling flush guide. Dual-boiler E61 machines are calmer here, but a long slow fill can still change how the group feels at the start. Taste water temperature as its own variable the day you change the soak length.

One coffee, one basket, a scale

Bottomless portafilters make channels obvious. They are optional. A scale is not. Stop on weight, not on a vibe. If you also change grind “to suit the profile” in the same session, you will not know which change you liked. Grind moves are allowed the next session, after the orifice has a verdict.

Use this: no group gauge, no frozen baseline, no valve experiments. The kit can wait in the drawer.

A Three-Session Routine You Can Repeat

This is a kitchen routine, not a lab protocol. It assumes the machine is hot, the group is flushed the way that machine needs, and the valve is marked. Put a piece of tape on a knob, or a paint dot on a paddle arc, at “full” and at “soft.” Full means as open as the kit goes. Soft means a trickle you have already tested into an empty basket: slow water, visible, not a sealed shut-off.

Session A — prove the machine without the toy

1. Valve fully open. Dose and distribute the way you will use all week.
2. Lever up. Start the timer. Stop at the target beverage weight.
3. Log time and taste. Repeat twice more.
4. If the three times disagree by a wide margin, or the bottomless pour sprays, stop the project. Distribution and grind are still the story. Channeling stripes are not a pressure curve.

Session B — add only a soft start

1. Same dose, same target weight, same coffee.
2. Set the soft mark. Lever up. Watch the group gauge stay in a low band and watch the basket wet.
3. When drops are a steady thread—use a count you can repeat, inside that 5–15 second working band—open to the full mark in one move. Do not hover.
4. Stop at the same weight as Session A. The total time will usually run longer. That is expected. You added a soak; you did not fail the shot.
5. Taste against A before you congratulate the kit. Sweeter or calmer at the same yield: keep the mark. Hollow and sour: shorten the soak by a few seconds and repeat. Harsher than A: the soak was too short to matter, or the flush ran hotter; do not grind finer yet.

Run Session B three times on the same mark. If you cannot hit a similar soak count and a similar total time, the mark is too close to shut, where tiny hand errors become big flow errors. Open the soft mark a little until the trickle is boringly repeatable.

Session C — one tail test, then stop

1. Pull one Session B shot as the control.
2. Pull one more. Same soft start, same full open, then ease slightly toward closed for about the last 5 seconds, and still stop on the same weight.
3. If you miss the weight, discard the taste note and try again. Yield changes masquerade as profile changes.
4. Keep the late close only if the finish is clearly less harsh and the sweetness holds. If the cup thins out, return to Session B forever. That is a successful test.

Light roasts are the usual reason Session B exists: dense cells, more resistance, more punishment for a violent start. Medium-dark blends are the usual reason to cancel Session C and often Session B. Write the coffee name next to the mark. A soft mark that flatters a washed light roast can strip a comfort blend the next week. Change coffee, rerun A, then decide whether B is even allowed.

Use this: three sessions, one change each, same yield. Anything more elaborate waits until these notes are dull.

E61 Kits, Saturated Groups, and Saved Profiles

An E61 flow-control kit belongs on an E61. The top cap, the cam, and the pre-infusion chamber are a matched stack. A saturated group is a different stack: the group is heated by brew-boiler water and the brew valve is designed for that body. Ordering an E61 needle for it does not add “café profiling.” It adds a part that does not fit. If you are choosing machines rather than retrofitting, settle the thermal design in E61 vs saturated group head first. Buy the flow-control story only after you know which group you will actually live with.

Some non-E61 machines leave the factory with a paddle or with electronic pressure profiling. That is a reason to pick that machine, not a reason to adapt an E61 kit across architectures. Compare total money and total habits:

• Keep this E61 and add a valve when the group is a standard E61, you like the heat behavior, a kit installs without machining, and you are happy to be the program (level 1, maybe level 2).
• Move to a machine with a saved profile when you want the same shape on every drink while you steam, or you do not want to service a needle seat.
• Stay stock when Session A already tastes right. The passive E61 chamber is the profile.

Hardware-plus-gauge for a home E61 kit often lands in a few hundred dollars before labor. A shop hour on top is common if you would rather not open the group. If that sum is close to the gap between your machine and one that already profiles, compare the gap honestly. Do not buy a valve because a video made the gauge needle look dramatic. Buy it because Session B has a job on the coffee you actually drink.

Café and light-commercial bars should default to stock or to a saved profile. A manual paddle can be a signature on a slow bar with one espresso at a time. It is a liability on a line of milk drinks. Train the recipe that a new hire can hit with the valve open or absent. Coffee machines in the catalog split along that line: home E61 machines where a later kit is plausible, and machines whose brew path was never meant to take an E61 top cap.

Use this: retrofit an E61 you intend to keep. Do not retrofit the wrong group. Do not retrofit a cup that is already finished.

Care: When the Valve Stops Telling the Truth

A needle seat is a small metal gap. Scale, coffee oil mist, and a dry gasket turn “the same mark” into a different flow. The symptom is boring and expensive to misread: yesterday’s soft mark suddenly runs fast, or the knob sticks and then jumps. People answer by grinding finer. The bed was innocent.

Treat these as valve problems, not recipe problems:

• The tape mark used to take ~10 seconds to show drops and now takes 3, with no grind change.
• The knob or paddle feels gritty, or it will not hold a position.
• Water weeps at the top cap after a shot, or the portafilter stays pressurized when the lever is down.
• The group gauge twitches at a mark where it used to climb smoothly.

Maintenance is ordinary espresso hygiene, plus respect for that seat. Backflush on the schedule you already use. Descale when your water requires it—the machine manual wins over any blog interval—and follow a real procedure such as how to descale an espresso machine rather than forcing a seized knob. Hard water makes this kit a worse idea; if you already fight scale in the boiler, a needle will fight you too. Do not scrape a seat with a pick. If the valve still sticks after a proper descale, it wants a service kit or a technician, not more torque.

Gaskets you disturbed during install are part of the first month’s watch. A leak at the cap is a seating issue. Cam lubricant and the yearly group service stay on the E61 ownership list in the group-head guide; flow control does not cancel that work. Once or twice a month, pull a fully open shot and compare it with your original Session A notes. If the “full open” shot has drifted, the machine drifted. Re-baseline before you trust any soft mark.

Use this: a mark that moved is a maintenance event. Re-prove full-open behavior before you rewrite the profile.

Common Mistakes

1. Buying the kit to cure sour shots. Sour at a short time and a low yield is usually grind, dose, or temperature. A long trickle on a coarse puck makes the sourness longer. Confirm with sour or bitter espresso before you buy hardware.
2. Profiling the panel gauge. If that dial reads the boiler or the pump side, it can sit at the OPV setting while the puck is barely wet. Move a group gauge into the decision or stop claiming you saw a curve.
3. Changing grind, dose, and valve position on the same morning. You will prefer one cup and be unable to order the same cup tomorrow. One variable per session.
4. Holding a half-open valve for the entire shot and calling it a modern profile. If the group never reaches a real brew plateau, you brewed a long, weak shot. Open fully after the soak unless a paired taste test says otherwise.
5. A long soak on a dark, fast blend. Body drops, the shot tastes papery, and the coffee gets blamed. Stock lever, valve open, is the right profile for many of those bags.
6. Dead-heading the pump. Fully shut plus pump on is not pre-infusion. Open until water moves.
7. Expecting the paddle and the needle to extract differently when both are just orifices. The cup changes when flow changes, not when the handle looks more professional.
8. Ignoring the HX flush after you add ten seconds of slow flow, then “fixing” the hot shot by choking the valve further.
9. Installing an E61 kit on a saturated group because the video used the same word, profiling. Wrong part.
10. Chasing a falling tail on a shot that gushed in the first seconds. The channel already happened. Late restriction changes the end of a damaged shot.

FAQ: Espresso Flow Control and E61 Pressure Profiling

Is espresso flow control the same as pressure profiling on an E61?

They meet in the cup, and they are not the same control. Espresso flow control is the orifice—needle or paddle—that sets how fast water can enter the group. Pressure profiling is the pressure shape over time. On a manual E61 the shape is a consequence: restrict flow, and group pressure rises more slowly or settles lower until you open up, provided the puck resists. An electronic profiler targets bars directly and can save the shape. A knob cannot. Use “pressure profiling” for the goal, and use “flow control” for the tool in your hand, or you will shop for the wrong machine.

Should I buy a needle valve or a paddle?

Buy a needle knob if you will mark a soft opening and a full opening and leave them alone. Buy a paddle if you will practice two or three sweeps on a timer and you want that motion to be fast. If the paddle kit is a needle with a lever on top, expect the same hydraulics and a different hand. Skip both until open-valve shots repeat. Typical hardware bands are roughly $150–350 for many needle kits and $200–450 for many paddle kits, before a group gauge and before labor.

Will flow control fix channeling?

A gentle start can reduce early channels on a dense bed that is already evenly prepared. It will not repair clumps, a tilted tamp, a cracked puck, or a basket full of boulders. If a bottomless portafilter sprays with the valve wide open, fix distribution and grind. Then retry a short soft start. If it still sprays the moment you open to full, the bed is the problem and the profile is a spectator.

Do I need a pressure gauge to use an E61 flow-control kit?

You need a group-side gauge if you want to know what the restriction did. The panel gauge on many heat-exchanger machines is the wrong instrument. You can pull a soft start by eye—slow darkening, then open—but you cannot defend a “bar profile” without the group reading. Budget the gauge with the kit. Learn which dial is which in the pressure gauge guide before you argue with a number.

Can I add an E61 flow-control kit to a saturated group?

No. The kit is for the E61 top works and chamber. A saturated group needs its own brew valve, its own pre-infusion feature if the manufacturer gave it one, or a machine that was designed with a paddle or a saved profile. Compare the groups in E61 vs saturated group head, then choose a path that fits the metal you own.

Who should skip pressure profiling entirely?

Skip it if your stock shots are already the cup you want, if you are still learning grind and yield, if you have no group gauge, if you need café speed, or if you want a saved bar program and this machine cannot store one. The stock E61 mechanical soft start is enough for a large share of home espresso. Add a valve when a specific coffee is better with a longer marked soak and you have the notes to prove it.

What to Do Next

Pick the next step from the machine in front of you.

• You do not own the machine yet. Decide E61 versus saturated in E61 vs saturated group head, then browse coffee machines with that group in mind. A paddle is optional later. The group design is not.
• You own an E61 and shots still wander. Read espresso pressure explained and espresso pre-infusion explained, then spend a week on dose, yield, and distribution with the path fully open. The kit waits.
• You own an E61, Session A is stable, and light roasts still start harshly after good prep. Add a group gauge and either a marked needle or a paddle you will actually sweep. Run Session B. Keep it only if the same yield tastes better.
• You own a saturated group or you want the profile saved while you steam. Use that machine’s own pre-infusion or electronic profiling. Leave E61 kits on E61 groups.

Flow control is a small orifice and a disciplined hand. Pressure profiling is the shape you earn after the orifice, the puck, and the OPV have all had their say. If you can mark two positions, freeze the yield, and say whether the cup got better, you have the whole practice. If you cannot, the lever alone is the better barista.