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.

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