This morning I connected my Micro Casa a Leva to the power, noted the time, and then went outside to saw down some small trees. After 45 minutes I came back into the house and prepared a 15 gram shot of a central American coffee with 20% robusta added. I used the La Pavoni 49mm bottomless portafilter. I pushed down the handle, waited 10 seconds, allowed the handle to rise under my control until just a few drops emerged, recocked it, and then released the handle. Through the entire shot I monitored the temperature of the emerging espresso. It very quickly rose to around 85 degrees, and then by the time the shot was about a third to half finished it was up to 90.5. What is amazing is that it remained just at 90.5 through the entire rest of the process! Ambient temperature was 22. There was a lot of crema. Taste was great.

When I pull the shot three minutes after the machine reaches temperature, and allow about 15 mL of water to pass through the group before attaching the portafilter, the temperatures generally run around 87 to 88 for most of the shot.

I have always noticed that the MCAL temperatures tend to be rather constant during the pull after the first few millilitres. I suspect this is due to the fact that the group is designed to be heated by conduction, and gets heated rather evenly as a result of the wide brass connexion between the boiler and the group.

This is dramatically better temperature stability than with second generation La Pavoni machines with the steam heated from the top group. The temperature with the MCAL is much more constant during the pull.

What I should do is run another experiment and leave the machine on for an hour and half or two hours to see what final temperature results.

I am curious as to what would be the result of such an experiment with an Olympia Cremina with its HOT Water heated from the top group design.

The more constant espresso emission temperature of the MCAL means that the temperature at the end of the shot is probably best a bit lower than with the La Pavoni 2nd generation because of the way the La Pavoni temperature rises during a shot.

To do this properly one needs to know precisely where the IR senstive spot is, on most of the IR thermometers it is just below the built in laser pointer. It works best with the device only about 8-15 cm from the portafilter, and with the beam pointing upward at about a 45 degree angle. You want the centre of the IR sensitive area pointing at the centre of the bottom of the dispersion screen.

NOTE again. What I am measuring here is the LIQUID emerging from the bottomless portafilter at the instant it emerges.

Robert,

Very interesting and thank you. What year is your MCAL and do you have the stock group to boiler gasket in place?

Scott

This is a 2013 model MCAL. It is almost completely stock, except for a steam tip and steam valve knob.

When one is attempting to set up temperature control systems, to me, it is ultra important that one evaluate the really important temperature--and to me that is obviously the temperature of emerging espresso. This is easier than any other method I have seen, and seems to work best.

To me the MCAL is a truly wonderful machine, but one must be ultra careful about contaminated water, and one must be very precise with getting the correct grind and tamp. MCAL users also need to develop a precise techniques that work best for each user's needs.

Great post, Robert!

rpavlis wrote:To me the MCAL is a truly wonderful machine, but one must be ultra careful about contaminated water

As our resident chemist, could you please remind us of the water composition that you use with your La Pavoni and MCAL?

In my town the water is amazingly hard and also amazingly alkaline. It is so bad that one needs to descale pots and pans after boiling vegetables! It would be death to any espresso machine in a short time. I gave a colloquium at the University two or three years ago, and in the course of that I outlined the analysis of coffee ash. It is apparent from the analysis that the coffee is extremely rich in potassium. There is also substantial magnesium, and somewhat less calcium than Mg. There turns out to be MORE Mg and Ca in a the beans than in the hardest water! Oddly there often is more rubidium than sodium in coffee. The thing that is lacking from purified water (distilled or otherwise purified) that is obviously important in coffee brewing is bicarbonate ion because it neutralises some of the acids in the beans and also is a pH buffer. Brewers, especially wine makers, often use potassium bicarbonate to neutralise sour wines, so it is very readily available. Because there is so much potassium naturally in coffee, we really are only increasing bicarbonate signficantly by adding it. There can be a lot of sodium in ground water, but often not.

Chloride ion in water is terrible because it complexes copper ion, and this can, and will, start a serious corrosion cycle, especially in slightly acidic water, but it is bad any time. The space above the piston in the MCAL runs dry, and when water stays in the pores of the walls it evaporates and deposits chloride and other things on the wall. As more and more accumulate the result will sooner or later be pitting and corrosion. Elektra is very aware of this, and warns buyers of their new machines that they will not honour guarantees if customers use contaminated water.

Thus I take distilled water and add to it 50 to 100 milligrams of potassium bicarbonate per litre. This produces a concentration of bicarbonate similar to hard water that cannot produce scale. Light roasts do not taste like lemon juice or vinegar, and composition of the espresso is not altered by pH shifts because bicarbonate is just as good a buffer with potassium as with calcium and Mg. Actually it is better, because it remains at constant concentration and you are not at the mercy of the local water company as to its composition.

I usually make a 10% solution of potassium bicarbonate in water and add 1 mL of this per litre of distilled water. These days one can purchase very good electronic balances that weigh to at least two decimal places. If you mix up 4 litres of water, you can weigh out from 0.20 to 0.40 grams of potassium bicarbonate and toss it in and stir, it is highly soluble. You will never get any scale with this and it will have the brew water at about the ideal pH for brewing, and also at about the most stable pH for brass and copper stability, most important there is no chloride in it to pit the MCAL's group walls. I have tried sodium bicarbonate, but it just does not seem to taste quite right for me.

Also, the analysis of coffee ash shows quite a lot of chloride. Thus brewed espresso is quite corrosive, and that is made worse by the fact that brewed espresso, even with bicarbonates present is slightly acid. That is why you find espresso machines with sheet metal bases suffering from severe corrosion. One must clean them immediately after each use, and avoid allowing any espresso getting under the base.

One more question, please, Robert. What is the manometer reading once the machine is idling? Thank you.

Perhaps a topic for another thread, but I am curious about the different gaskets Elektra has used between the group flange and boiler and they impact the temperature of the group and ultimately the shot. The early style thick paper gasket vs. the later style o-ring. Add in the custom or modified teflon heat break gaskets (or repurposed Ponte Vecchio Export gasket) that have been mentioned in other Microcasa a Leva discussions, so there we have three or four variations, each that I would think have different heat conduction properties.

Scott

This machine's pressurestat results in its rising to about 1.3 bar on initial warm up. After a few minutes, however, it stabilises right at 1.0 bar. I have often wondered it this behaviour were built into the pressurestat, it surely is a good thing. It makes the boiler hotter initially, then it cools down a bit.

Thanks Robert. You machine being a 2013 probably has the Mater pressures-stat, correct? My 1991 machine has the older style brass, exposed plunger, and separate micro-switch assembly and exhibits a similar initial high temperature on startup followed by decreasing temperature. Stabilization for me seems to take about 20 minutes, though. Since we probably have different pressurestats, I wonder if there is something else in the design of the machine that leads to this phenomenon. Some more discussion about this going on in Original pressurestat behavior on 1988 Elektra Microcasa a Leva

The 2013 indeed has the Mater pressurestat.

I agree that exit temp probably has more to do with taste than the temperature measured above the coffee.

While shot-to-shot repeatability is always good, I usually find temperature stability (a single, fixed brew temp during brew) to be a negative. Ask any coffee roaster what they think about the idea of "temperature stability".