Given the importance of temperature stability (and predictability) when making espresso, why is it not more common to pack the grounds in the portafilter basket and detach the PF from the group head only for the time it would take to pop in the basket?

I can only think of one reason and that is the convenience of baskets that are held in the PF . . . it is much easier to knock out the grounds, but 'snapping' in the basket would disturb the tamped grounds.

but but but . . . the PF must cool down quite a bit while away from the machine . . .

Henry

(hoping this is not a dumb question!)

hbuchtel wrote:Given the importance of temperature stability (and predictability) when making espresso, why is it not more common to pack the grounds in the portafilter basket and detach the PF from the group head only for the time it would take to pop in the basket?

(hoping this is not a dumb question!)

Not dumb at all. That very issue has been subject to a heated debate for sometime now. I prefer dosing and tamping directly to the basket for the very same reason. I covered it in detail in the Brewtus Review. Following is an excerpt:

1) It increases thermal stability in my experience. Detaching the portafiler from the group for 30-40 seconds to dose and tamp reduces both the grouphead and the portafilter temperature.
2) Dosing directly into the basket allows the barista to rotate the basket 360 degrees for improved distribution.
3) It is easier to level your tamp when you tamp into a flat basket.
4) The coffee stays at room temperature until you are ready to pull the shot. Dosing and tamping into a hot portafilter starts "cooking" the coffee prematurely.
5) When entertaining a party, it is very efficient to line up all the tamped baskets (I have five) and shoot them back to back.

Abe Carmeli wrote:4) The coffee stays at room temperature until you are ready to pull the shot. Dosing and tamping into a hot portafilter starts "cooking" the coffee prematurely.

no, not really, and especially not if using a room temp basket.

barry wrote:no, not really, and especially not if using a room temp basket.

Come again? What is the coffee temperature then?

sorry to be a bit abrupt today... it's the day after thanksgiving, i work in a mall, and i'm roasting non-stop.


the basket is insulated from the portafilter by an air gap. the majority of puck heating is radiant heat from the showerscreen. the stainless basket is a relatively poor thermal conductor, and the coffee grounds are even worse thermal conductors.

i've done some datalogging tests with probes at various points within the puck and on the portafilter and basket (8 channels is great for this sort of thing). the top millimeter or so of coffee only reaches 100F after about 60-90 seconds (ballpark, i'm going from memory on this one as i don't have time to look it up). coffee deeper in the puck comes up at an even slower rate. the bottom line is there is usually plenty of time to dose, tamp, and initiate the brew cycle w/o causing undue thermal stress on the grounds.

barry wrote:i've done some datalogging tests with probes at various points within the puck and on the portafilter and basket (8 channels is great for this sort of thing). the top millimeter or so of coffee only reaches 100F after about 60-90 seconds (ballpark, i'm going from memory on this one as i don't have time to look it up). coffee deeper in the puck comes up at an even slower rate. the bottom line is there is usually plenty of time to dose, tamp, and initiate the brew cycle w/o causing undue thermal stress on the grounds.

Got you. For a moment I thought that you meant that when grinding directly to the basket, the coffee does not remain at room temperature. What's on the roaster's menu today, and where do you vent all that smoke?

Abe Carmeli wrote: What's on the roaster's menu today, and where do you vent all that smoke?

so far today i've done:

DSB
espresso roast
2 batches of costa rican for flavors
a batch of costa rican for costa rican
french roast
d-colombian
d-sumatra
colombian

i don't know what more i might need; that changes minute by minute.

smoke goes 8 ft vertical, 13 ft horizontal, and 26 ft vertical up along a support girder and out through the mall roof. we're on the lower level of a two level mall, so exhaust location was very limited.

Do you all have any measurements or estimations of how fast the PF cools down?

Assuming about 30 seconds for dosing and tamping (me!) how much heat would be lost?

Henry

yes, i do, but i can't look it up for a few hours.

hbuchtel wrote:Do you all have any measurements or estimations of how fast the PF cools down?

Assuming about 30 seconds for dosing and tamping (me!) how much heat would be lost?

Henry

I made an attempt to answer that question a while back. What the significance of the answer may be, I don't know.

AndyS wrote:
I made an attempt to answer that question a while back. What the significance of the answer may be, I don't know.

This correlates with my own data. Another interesting side effect is the cooldown of the grouphead. When you detach the P/F, there is a noticeable drop in grouphead temperature. I'm going to take some measurements today and post them. My only caveat is that I do not have thermal grease and that will probably affect the T/C reading.

Thanks for your replies. I should have checked alt.coffee first! My own interest in this is less about stability and more about simply getting the temperature up as I am using a Presso, the pour-over type lever machine.

It seems this could be quite relevant for other espresso machines as well . . . especially after reading Chris' entries about the GS3 and <1 degree measurements affecting the taste.

Henry

hbuchtel wrote:I can only think of one reason and that is the convenience of baskets that are held in the PF . . . it is much easier to knock out the grounds, but 'snapping' in the basket would disturb the tamped grounds.

Abe (and others) didn't mention that you can remedy the "snapping" by removing the basket retainer spring. Still, take care when putting the basket back in the portafilter.

I've also always experienced that the faster the (skilled) barista (and thus the less time the pf is out of the group), the better the espresso... compared to a slower procedure (but all other things being the same).

I just pulled me a double just now on our Linea... 27 seconds between grabbing the pf to hitting the brew button... and we flush both times.

I'd love to see some testing done (on a commercial machine or more specifically, one with a hot-water spout) on pre/over-heating the portafilter between grabbing the portafilter outta the machine and dosing. What's the ideal temperature for the portafilter body relative to the brew water temp?

Keep in mind, these techniques really don't improve the espresso, so much as they preserve what's already there. Not a big deal, but a distinction worth mentioning. The effects related to temperature of the portafilter are negligible when you've got a crotchless (that is, in real-world situations... I've taken a crotchless down to single-digits Celsius and you'd better believe the espresso brewed cold).

Nick wrote:Abe (and others) didn't mention that you can remedy the "snapping" by removing the basket retainer spring. Still, take care when putting the basket back in the portafilter.

Actually I did mention it in the Brewtus Article, and it is a very important point. Without removing the retainer spring, you will upset the coffee puck when you snap the basket back in and that in turn may cause channeling. Using a ridgeless basket is another option, and if you do it carefully, you can keep the retaining spring in place.

I just finished a series of temperature tests on the grouphead. I detached the portafilter and watched the grouphead temperature for 40 seconds. The decline in temperature is negligible. However, I measured it without thermal grease as I mentioned earlier, which may have affected the accuracy of my readings. I attached the T/C to the top of the grouphead and applied downward pressure using my hand and a paper towel for insulation. A better way to measure it is with a T/C inside the grouphead.

here's a graph from a test run from a couple of years ago. i did a more substantial series of warming/cooling tests, but i need to find the notebook before i start posting graphs.

barry wrote:here's a graph from a test run from a couple of years ago. i did a more substantial series of warming/cooling tests, but i need to find the notebook before i start posting graphs.

Barry, did you take into account the small amounts of kinetic energy that is transferred to the portafilter (and then becomes heat energy) as the barista moves the portafilter around? I mean, if you just left the portafilter on the counter and took measurements, you're not really taking into account all of the different factors that can effect the temperatures. As the portafilter is handled by the barista, you have not only the energy created by the tensile stress on the metals as it's being handled, but the heat from the barista's hand as well. Of course, you'd have to take into account the height, weight, and ethnicity of the barista.



Ugh... I just got through pulling shots for 5.5 hours straight with little breaks only to wash my hands of coffee grounds... and my brain is mush. Just for kicks, I'd vary the speed at which I worked... to see if there would be any visual variation. Generally speaking, the darkest crema came with the faster barista-ing... consistent with what I've experienced in the past. I got my pf-grab-to-brew time down to 20 seconds (with some tweaks to my workflow)... still with both a cleaning and preheat flush.

Nick wrote:Barry, did you take into account the small amounts of kinetic energy that is transferred to the portafilter (and then becomes heat energy) as the barista moves the portafilter around? I mean, if you just left the portafilter on the counter and took measurements, you're not really taking into account all of the different factors that can effect the temperatures. As the portafilter is handled by the barista, you have not only the energy created by the tensile stress on the metals as it's being handled, but the heat from the barista's hand as well.

ummmm.... well.... not in the test that is graphed above.

in the other tests, then yes, i did. i ran tests with the pf on the counter, and waving it in the air like it was being dosed, tamped, etc. i think i did a couple of other versions, too, but, again, i need to find the notebook.

Nick wrote:I got my pf-grab-to-brew time down to 20 seconds (with some tweaks to my workflow)... still with both a cleaning and preheat flush.

That's moving! I just timed myself... 45 seconds. The Mini suddenly seems slow when you're watching the seconds tick away.

HB wrote:That's moving! I just timed myself... 45 seconds. The Mini suddenly seems slow when you're watching the seconds tick away.

When the grinder seems slow... make up for it by grinding earlier.