Thanks for all of the input and ideas. I wanted to add a thermometer that would be somewhat inconspicuous, insulated from the heat of the machine, and removable so the group could be taken off. I decided to combine several great ideas in this thread with installing a Teflon group/boiler gasket.

I placed blue painters tape over the boiler attachment plate and used a pencil lead to rub and define the edges and holes. Then I pulled and placed the tape on a Teflon sheet, first cutting the large circle with an Exacto knife, then the outline with scissors (including the protruding tab I had drawn on), and finally the bolt holes with a drill.

I used Sugru to attach the end of the sensor probe to the group bell as well as mount the thermometer display on the tab protruding from the gasket . Two little packets of Sugru was enough and easy to work with. I did use some tape to hold the thermometer display aligned while it cured. The tab holds it really well. There is enough slack in the probe wire so only the end touches the machine and there's room to slip the display up off of the tab.

Matt inspired me to try a Teflon heat break gasket* with a tab for attaching a thermometer. I'm also using stainless Taylor Elite thermometers that go with the chrome on the machine. They face upward so you can watch temperature while standing over the machine. Matt's innovation of a gasket tab eliminates the need to attach anything to the group or group neck. My latest variation holds the thermometer stable with a tiny clamp and miniature screws. I've added Permatex blue thread lock to the nuts to keep them in place.

At first my tab was as long as his. I liked his idea of forming a template using blue painter's tape.



I used hole punches to get it in shape.



I thought I would align the thermometer shaft with two clamps. To drill the tiny holes I used a Dremel sized rotary tool with a Dremel collet set and tiny drill shafts. The clamps proved difficult to align and in the end the tab was too long so the thermometer was held too high.



So I snipped off one of them.



I cut the thermometer steel shaft so there was enough remaining to be inserted and clamped down. I punched the hole through the tab with the idea the sensor might be threaded behind, but this left the wire a bit short, so I abandoned that idea. Now it looks like Caspar the friendly ghost!

I thought of attaching the probe to the back of the group with Sugru and realized if I remove the group to service it, there goes the Sugru connection, so I returned to the group gasket o-ring to hold the sensor tip in place.

The next post shows the thermometer in place with this reworked tab.



* If installing a do-it-yourself heat break gasket instead of a factory spec part, for safety, be sure to install bolts that are longer by at least the extra thickness of the gasket. You'll want to have the bolt turn in by six full threads of engagement into the boiler, keeping in mind that any modifications to factory specification are taken at your risk as per the terms of use that you agree to when accessing this site.

Here's my Europiccola with glitsy mods, a Taylor Elite thermometer on the group, a metal sightglass and chromed drip grate.

drgary wrote:Here's my Europiccola with glitsy mods, a Taylor Elite thermometer on the group, a metal sightglass and chromed drip grate

Very smart! +1

I just added a thermometer to the outside of the group, similar to Dr Gary's, but not nearly as nice. I noticed that if I just lift the lever to release false pressure without flushing any water through the screen, the group temp rises to around 165F. After a couple of pulls, the temp can go as high as 190F. I have a couple of questions for you guys :

1. What is a good starting point for me begin my search for the ideal temperature?
2. Is channeling more likely when the water temperature is too low? I have found that the first pull in the morning tends to come out fast and out one spout only. The second seems to be fine.

I use 14.2g in a double Millenium basket and a very light tamp.

Thanks in advance,

Winston

On my Millennium model Europiccola I find that the outside group temperature is slightly above the brew temperature. How do I know this? I picked up a local coffee that's roasted in a Nordic style and needs to be brewed hot. I had to heat the group to 214F outside temperature to get it to move beyond sourness to sweet, pit fruit flavors with no bitterness. This means the water inside the group was not boiling even though the temperature on the group was above boiling. Similarly I just pulled a coffee sourced at another local roaster who told me to pull it at 200F. I heated the group to 203F and the shot was just right. For dark roasts into second crack, where the beans are fresh but oily, I may start with the outside group temperature as low as 179F. This tames the bitterness and makes something more like Alan Adler suggests with an AeroPress. He likes coffees taken just into second crack and suggests brewing at 175F. (For lighter roasts on an AeroPress I take it to the recommended brew temperature, not 175F.) Your Romantica may yield a different outside group temperature than a Europiccola, so you'll need to dial in a coffee and use the outside temperature as an indication rather than an accurate reading of brew temperature. To approximate more closely you could insert a temperature probe at the top of the coffee cake and compare its reading to what you're getting outside the group. But I don't think that's necessary. All you need to do is correlate your measured external group temperature with different roast levels to get a feel for it.

Your initial channeling problems may be caused by a residual air pocket in the group. Before pulling your first shot, try purging some water through the group and the steam wand. This will avoid a spongy pull and a first shot that is not as good as those that follow.

It would be interesting to take the specific heat of ground coffee and the depth of the ground coffee in the filter basket and try to model the temperature change in time. The coffee is initially near room temperature, and it soaks up a lot of heat from the initial hot water, so that the first part of the extraction is done at far lower temperature than after some water has passed through the plug. If one measure the temperature of the espresso as it exits the portafilter, one sees that there is a sudden point after several millilitres of espresso have been produced where the temperature climbs a lot very quickly.

I have used this device a lot since I made it:

La Pavoni spout thermometer well

There are many points where temperature can be measured. I think the best after the fact point is the spout. That enables one to see what to do the NEXT time. I suspect the best before the fact temperature measurement is still near where the portafilter attaches to the group, especially 1974-2000 groups.

FWIW I have found the simple external measurement sufficient for consistent pulls.

Thanks, Dr. Gary. I have never considered the possibility that the brew water is cooler than the outside of the group. All the threads on non-lever machines have talked about the boiler (PID) being hotter. I just assumed likewise. This is very good to know. Thanks. The highest temp reading I have seen is 190F-195F. Under what conditions would I need to use your cool PF trick? After inserting a cool PF, the reading drops to around 180F.

My start-up routine is to push the lever up to force air into the boiler, but only allowing a few drops of water to come through the screen, and then run some steam out the wand. I often repeat this procedure. As a result, I don't get spongy pulls. With the new thermometer, I can see that the group is only at 160F or lower. I am pulling too cool. The coffee is Zoka Cuatro, brown with no oils on the surface. Will try flushing water out the screen to raise the temp tomorrow.

Prof Pavlis, I tried plunging an oven thermometer into the spent puck and got a bit of a "sneeze" as reward . The temp reading was somewhere around 160F which I discounted, assuming the probe was sinking away too much heat. Given what Dr. Gary said, the reading was probably correct.

Thank you both for the suggestions.

Winston

Winston, to check the temperature at the coffee cake you can insert a very thin thermocouple or you can sacrifice a filter basket and thread the probe through the side or bottom and make sure the probe is at the top of the coffee cake.

The boiler temperature is higher than at the group. To increase temperature in the brew group use half pumps that do not allow water into the coffee cake. Try this without a portafilter inserted. How high can you raise the lever before water flows? Just short of that is where you want to go.

BTW I am not discounting Robert's measurement suggestions but am saying that the simple method of measuring temp on the outside of the group works sufficiently for me. Prior to this I tried to do that with adhesive temperature strips but that didn't give me enough accuracy.

Winston, to know how high your temperature measurement needs to go for that coffee, you'll have to dial it in by taste. Here's the link to those simple instructions by Jim Schulman.

Espresso 101: How to Adjust Dose and Grind Setting by Taste