Great HX shot without flushing?

Need help with equipment usage or want to share your latest discovery?
alexjp
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#1: Post by alexjp »

I have a Rocket Classic (a HX machine). I'm usually careful about flushing before I pull shots, but this morning I was distracted. The machine had been on for 5 hours and sitting idle for almost 2 hours. I ground, tamped, and started a shot without any flushing whatsoever. 25 seconds later, I realized what I'd done and stopped the shot, mortified. I went to get the sugar, assuming the shot would be badly burned, but decided to try it before adding sugar.

The shot tasted great - excellent balance; not excessively bitter or harsh at all. I'm using Teodoro beans from Nossa Familia in Portland, which they describe as medium dark; I'd say they're a shade lighter than the Dolce blend from Espresso Vivace.

How is this possible? Could it be that my flushing routines are not as necessary as I've been led to believe? My two hypotheses:

- Perhaps 5 hours of warmup changes the way the machine responds? On weekdays it warms up for 30 minutes before I make coffee.
- Perhaps the darker roast is more resilient under high temperatures?

Has anyone else had success with HX machines without flushing?

-Alex

LukeFlynn
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#2: Post by LukeFlynn »

I believe the Rocket has flow restrictors, which prevent the group from getting too hot from idle HX water. The thing is, every single HX is different, I guarantee you when I had my Oscar, if I pulled a shot without flushing it would taste awful. This is what is called a dragon HX, and a flush is mandatory. If I assume correct on the Oscar having restrictors, it will not be mandatory to have a flush routine. You could be using a forgiving coffee, which may taste palatable anywhere from 197-206 degrees.

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zeb
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#3: Post by zeb »

Flushing a hx machine is only useful when setting is too hot. Or to clean the group.

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another_jim
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#4: Post by another_jim »

It depends on the machine.

The ideal HX machine, after a long idle, has a slightly cool head that gets warmed up to the correct temperature by the too hot HX water, while in turn that water is cooled down to the right temperature. After this, the head cools down at a rate that compensates for the water in the HX heating up, and everything remains copacetic. Only a few very expensive commercial HXs are tuned this perfectly.

Thermosyphon loops can be tuned to get close to this; but in the past this was rarely done. More recently, this has changed, and there are more thermosyphon machines that can be used without flushing.

Well designed home machines without thermosyphons also work in the same way. The Elekra Semi with a bolt on group and all the Bezzeras with bolt on and actively heated groups idle at lower temperatures and are heated by the incoming HX water. Their unflushed first shots are also acceptable.

The drawback with these in range first shots is that while the temperature remains in the correct range, they start cooler, and end up hotter; whereas follow on shots start hotter and end up cooler. This change in the temperature profile makes for slight change in the taste between first and follow on shots. Therefore, many people still prefer to give the group and HX a flush to get to the standard temperature profile.
Jim Schulman

F1
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#5: Post by F1 »

@alexp

What is your elevation?

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CoffeeBar
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#6: Post by CoffeeBar »

another_jim wrote:
Only a few very expensive commercial HXs are tuned this perfectly.
.
Hi Jim, May I know what brands and models are these expensive commercial HX Machines? Thank you

alexjp (original poster)
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#7: Post by alexjp (original poster) »

@F1, I'm at more or less sea level. Bought this machine after I left Colorado.

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another_jim
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#8: Post by another_jim »

CoffeeBar wrote:Hi Jim, May I know what brands and models are these expensive commercial HX Machines? Thank you
The NS Aurelia most prominently; it may be the most temperature stable machine on the market. The KdW Mistral and Faema Legend are luxury machines with superb stability. The latest top of the line regular Cimbali, Faema and Rancilio models are also extremely stable.

Note: these are all multi group machines that require 220V; so not particularly practicable for the home. For working bars, they are all excellent choices. However, 3rd wave bars invariably use double boiler machines, not top of the line HXs -- not because they are better, but because they are one of the expected signifiers of high end coffee.
Jim Schulman

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CoffeeBar
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#9: Post by CoffeeBar »

Thank you Jim :wink: