Just for practice, if you shut the thermometer off and use the same coffee, dose and grind, are your pulls consistent? That would be a place to start. What's nice about having a PID'd Amica for comparison is the pump pressure is always the same. The grinders that feed it are consistent (Pharos and SJ). Then it's on me to be consistent in dosing and puck preparation.

If you read the threads where the H-B team members review new coffees you'll see they tend to vary temperature by degree. They adjust other variables to dial in a coffee and mostly use very fine pump machines. I haven't seen them write about flow characteristics changing with temperature.

uyeasound wrote:Out of interest, at what temp do folks find their machine settles, with respect to their target?

My machines, if left on for 30 minutes or so become too hot. My pre-M pro has a ~1 bar pStat setting and gets way too hot. But my millennium, given enough time also gets a bit too hot if I turn it on and dawdle. It has a pStat set at .75 bar on / .85 bar off (slightly higher than factory setting, but I'm at 5000 ft altitude where the corresponding boiler temps would be 113C - 115C.)

My technique does not involve letting the machine settle. I turn it on, let it come up to pressure, bleed and pump off any possible trapped air, actively flush to heat the group head, and pull the shot. On the pre-M pro I always turn off/on the switch so as to brew well below 1 bar. After steaming I turn it off. If I'm making 2 or more in succession I cool the group - so my group temp is never really settled.

(I rarely make multiple shots on my Pavonis - I have an HX for that that I do leave on all day.)

With respect to your observation that a 0.2C temp difference noticeably affects the shot flow and taste, I have to agree with drgary that something else must be at work here. If small temp variations were that critical I'd be pulling mostly sink shots - I'm doing good to get the group in a 5 degree ballpark.

homeburrero wrote:My machines, if left on for 30 minutes or so become too hot. My pre-M pro has a ~1 bar pStat setting and gets way too hot. But my millennium, given enough time also gets a bit too hot if I turn it on and dawdle. It has a pStat set at .75 bar on / .85 bar off (slightly higher than factory setting, but I'm at 5000 ft altitude where the corresponding boiler temps would be 113C - 115C.)

I sometimes leave the Millennium machine on for hours and can still control temperature by cooling the stock portafilter. There's no thermometer on the group, just temperature strips. In San Francisco I'm at sea level, ever-rising these days -- I wonder if global warming is affecting our measurements?

I think we're in agreement - that the machine idles at a too-hot temp. In my case if it's been on for a long while before I start making my coffee I get my OE 3rd shot out of the freezer. I suppose I could leave the machine on and do that as a routine. I don't generally do that because after my Pavoni wake-up coffee (best coffee of the day) I switch to my HX machine - I'm still struggling to achieve proficiency on that one.

drgary wrote:I wonder if global warming is affecting our measurements?

Maybe so. Or perhaps your water is exposed to more positive thoughts than mine http://www.randypeyser.com/emoto.htm

Been there done that...

Digital temperature controller on a lever machine

My new thermometer arrived today. It offers a much faster response to change, and it has shown that my old one wasn't reacting to some drastic swings in temp. Sometimes the old one was off by as much as 5degrees.
This explains the variations i was seeing in the flow and in the cup.
It goes to show you get what you pay for...

Glad you've got a better thermometer. I don't think it explains the variations in the flow, but in the cup for sure!

uyeasound wrote:My new thermometer arrived today. It offers a much faster response to change, and it has shown that my old one wasn't reacting to some drastic swings in temp. Sometimes the old one was off by as much as 5degrees.
This explains the variations i was seeing in the flow and in the cup.
It goes to show you get what you pay for...

What is your new thermometer? I was using a cheap one from e-bay which reacted more slowly than my temperature strip. When I realised I was using my temperature strip to regulate my thermometer, I detached it from the group and returned to the temp strip only.

It's a Thermapen, and it's very responsive. It cost £36. No wonder i was pulling at wildly varying temperatures with the old one. Too much thermal resistance in the probe, whereas this new one measure at the tip.
The Thermapen is very accurate and fast, and it also has the benefit of not attaching to the machine (so it looks better - no wires hanging off it). But the downside is - it doesn't attach to the machine (meaning i have to hold it steady, in the same position each time). I've found a steady and repeatable way of holding it though, so it works really well.
I would definitely encourage anyone who uses touch, or a temp strip, to judge brew temp, to buy a fast-responding temp-probe. Essential.

The Polder thermometer I use is also very fast. For measurement without attaching a thermometer I could easily see using a thermocouple connected to a meter. I like having my Polder attached to the machine. If you look at the original posts the wire and thermometer aren't prominent.