The effect of grind settings on brew temperature

[Elbasso]

I've been testing a new blend the last two days. When experimenting with a new blend I usually start with finding a good grinder setting. Then I move on to finding the right temperature for the shot using eric's E61 grouphead thermometer. Today, after settling at a starting temperature of 197 F, I decided to tighten the grind a bit for more viscosity in the shot. The result was a bitter ristretto. On my next shot I watched the temperature during the shot. It was 3 to 4 degrees F higher then before the grind change. To me, this makes sense as the water gets stalled more by the higher resistance of the puck. To get things drinkable again I tried to lower the starting temp of the shot to 195 F. Even though this led to hitting the right target temp after about 14 seconds, it also introduced some unpleasant sourness. I guess 195 F was too low to start with. After wasting countless shots with starting temperatures ranging between 195 and 197 I started to try the flush and go technique while keeping 197 F as a starting point. This finally seemed to do the trick although my taste buds were quite numb by then.

I am wondering if others have experienced the same temperature behaviour and how they go about it. I've tried to find related topics but couldn't really find anything. It seems to me that anyone interchanging between espresso and ristretto should have some insight.

Cheers,

Bas

[BobS]

I've had some of that. Some espressos seem to hit it just right on the Andreja by flushing to 195, then
waiting 45 sec. before pulling. And others I've tried seem better by the - flush to 206, grind. tamp, flush
to 206, then pull the shot at the top of the heater cycle.

But, most of the espressos I've used lately have been designed for overdosing - 18g to 20g. And switching
from the Mazzer Mini to the Major or LaCimbali Max Hybrid has all but eliminated sour or bitter shots. I find
it a bit harder to dial in 14g to 16g shots, though most of what I pull are ristrettos. Some will be on the
verge of bitter.

Bob

[HB]

Today, after settling at a starting temperature of 197 F, I decided to tighten the grind a bit for more viscosity in the shot. The result was a bitter ristretto. On my next shot I watched the temperature during the shot. It was 3 to 4 degrees F higher then before the grind change. To me, this makes sense as the water gets stalled more by the higher resistance of the puck.

It may be more complicated than that. First of all, the temperature readings of Eric's thermocouple adapter will be more accurate at slower flow rates. And to make things really interesting, the OPV venting post-HX water to the reservoir will affect the overall profile, especially for slow, lower pressure pulls. Thanks to Ian for the reminder in With a smaller HX, what is a normal temperature drop over the course of a shot?

The Andreja OPV is on the output of the HX, so more cool water flows through the HX than on a machine where the OPV is before the HX. This contributes to the shot profile difference.

[Elbasso]

And switching from the Mazzer Mini to the Major or LaCimbali Max Hybrid has all but eliminated sour or bitter shots.

Oh no! I can feel a serious upgradeitis attack coming up. But seriously, does going from a high level home grinder to a professional grinder have such a big impact on the sour- and bitterness issues? I sincerely hope it doesn't. So does my wife I guess

It may be more complicated than that. First of all, the temperature readings of Eric's thermocouple adapter will be more accurate at slower flow rates. And to make things really interesting, the OPV venting post-HX water to the reservoir will affect the overall profile, especially for slow, lower pressure pulls.

Those are both very good points. But, does combining them (as in shifting from espresso to ristretto during a session) lead to a different shot approach?

CHeers,

Bas

[HB]

Those are both very good points. But, does combining them (as in shifting from espresso to ristretto during a session) lead to a different shot approach?

Could be. The OPV will vent more water at a low brew pressure (e.g., 8 bar) and lower the HX water temperature. I assume this will result in a lower brew temperature at the tail end of the extraction, especially for ristrettos, but I have not measured the effect on the Quickmill design. If you do, please let us know the result.

[Elbasso]

I would love to do some accurate measurements but that would require something like a Scace device and a TC I guess. Both are sadly not part of my current inventory. I'll ask around and see if I can get my hands on them.

[BobS]

On the grinder, if you re-visit the TGP and the Beat the Robur threads, one theme emerged - a longer
grind path means more consistency.

And that translates into either larger burrs or a conical burr set. I'd even argue that the Super Jolly
is on the verge of being too small for consistency; and yes, I've used a SJ for several days before
coming to this frame of mind. (I expect to get flamed for that last statement.)

I've noticed that I don't need to adjust the grind setting very often as beans age with the Major, a bit
more often with the LaCimbali. I used to do a lot more adjusting with the Mini just to find the right
spot. It could be with the shorter grind path the window for the grind setting is very small and the
consistency from shot to shot can vary more because the beans stay in the burrs longer. Or perhaps
the shorter grind path produces higher pressure that does more fracturing of the the beans than
grinding?

Regardless, I'm firmly in the camp that the grinder is more important than the espresso machine.

Bob