Continuous Flow

A graphic designer for LaMarzocco designed this symbol to indicate "continuous flow". In our repair shop, we are blessed with a continuous flow of espresso machines that are experiencing technical difficulties. This provides endless opportunities to explore espresso machine engineering insight that spans 5 decades.

As you know, with coffee, it is all about the water. These are just a few of the tubes that belong to a vintage lever machine we're working on. Heavyweight copper and brass fresh from de-scaling... (process by which lime scale and other mineral deposits are removed; like heart attack prevention).

Gorgeous blue oxidation on the outside of a 1963 tank. Oddly, there's no scale build-up inside the tank, so we're not going to dip this in acid. Check out the hydraulic engineering innovation here. One of us will be better able to explain how it works after it is re-assembled, but for now we'll tag it as beautiful and odd.

The devil is in the details. Here is a solenoid, responsible for metering water flow through the pipes. Notice how someone used teflon plumbers tape on a repair years ago. We don't recommend doing this because inevitably a shred of the tape will un-seat during installation and end up clogging an orifice down the line.

Orifices. That's what we have here. This is the dispersion screen, the sieve through which all water flows into the puck of fresh ground espresso. Does this look like a surface you'd want to eat off of? (No.) If you're favorite cafe doesn't keep this part clean, you're gonna taste a cup of yucky.

Water moves through those dispersion screens at about 200 degrees. The vast majority of espresso machines use an electric heating element like this one to heat the water. You can't see much of it here since the part that heats the water is inside the tank. What we can see here are the brass electrical terminals and almost antique porcelain insulators.

Nowadays, circuit boards manage the process control (how the machine operates). Automation is a wonderful thing...except when a chip, transistor, or gediddlehopper fries out. In the old country, they used a...

Mercury switch! This assembly rocks on an axis located to the right of the left red holder (you follow?) When the pressure on the inside of the tank falls below the desired point, this switch approaches level and the bead of mercury touches both electric terminals, and turns the heating element on. When the pressure rises, the switch begins to tip until the mercury rolls off one contact, breaking the connection and turning the heating element off.

The hazards of systems involving water and electric are well documented, but that's no insurance policy against incompetence. Take this masterful repair, for example: Using a sewing pin to temporarily fix a connection problem. Look on to the left side of the plastic bus for evidence of serial incompetence - it melted at some point prior due to a contact problem. Some common sense would be really helpful.

This gauge is would make a perfect pendant to dangle on a necklace of one of you coffee nerds. And what a statement: NO PRESSURE! Poorly executed maintenance and repairs eventually contribute to machine failure, often occurring at the worst possible time. Go slow. Take you're time. Fix it right.

The Faema President has so much style you can cut it with a knife and eat it with a spoon. Demand for old-school lever machines is definitely on the rise, especially if they're intact, and in fairly decent cosmetic condition.

In lever espresso machines, the "lever" is used to compress these springs. In the next movement, the pressure is then applied to water and pushed through the coffee. (This particular set of springs will need to be replaced.)

Let's call this the elbow. This is the joint that allows the smooth application of pressure to the spring.

OK, ok... let's wrap this slide-show up with another mercury switch and more insight into the intricacy of the mechanics of the earlier vintage machines. Over the years, a LOT of thought and craftsmanship has gone into building machines that will produce better coffee. Check out that delicate little spring in there.

It is good to be aware of the component parts and how they play nice to make great coffee extractions possible. It's all fun and games until you lose pressure.