Ruizs Place

When I first brought home my Gaggia Baby espresso machine, it had been used for a number of years, and not cleaned very well. I tried a few shots from it, but no matter what I did, they always came through too fast. When I adjusted my grinder to the point that the burrs were touching, the espresso would come out slowly at first (and look good), and get gradually faster until the shot was done after about 15 seconds. If you are having these issues too, its time to take a close look at the brew pressure of your machine.

The OPV, or over-pressure valve (also known as pressure relief valve), is fitted to most mid-level home machines with vibratory pumps. Vibe pumps aren’t really precision adjustable devices, so they are basically either on or off, and inside an espresso machine, whatever pressure they’re operating at is the pressure you’re getting through your espresso. In most espresso machine marketing literature, they advertise the power of pumps, 16 bar in this one, 18 bar in that one, but this really doesn’t matter - espresso needs about 9 bar, give or take, to be brewed properly, and this is where the OPV comes in. As the pressure raises, it will gradually open up to maintain a set pressure, usually about 9 bar in an espresso machine. Excess water is routed back to the reservoir, and the group head, and thus your espresso puck) see’s the proper pressure. Gaggia Baby and Classic models are fitted with an adjustable OPV, other models don’t have one, but if you can find one its a great upgrade for a Carezza or Espresso.

As you can read in some other posts here, the Gaggia machines are very easy to take apart and repair/clean, so while going through that process, I spent extra time on cleaning / restoring the OPV valve. It turns out that mine was completely sealed shut from past years’ scale deposits, and it wasn’t opening at all. I took the valve apart completely, and soaked it in a durgol bath and in a citric acid bath about 5 or 6 times - there was a lot of crud on there, and it took a while to get it off. Afterwards, things looked pretty good, and it was very easy to put back together.

When my machine re-assembly was complete, I hooked up my newly built pressure gauge, and proceeded to dial in the correct pressure. This is a bit complicated because the valve is not easily accessible, and adjustment requires disassembly of the valve. So its turn on machine, read pressure, turn off, unscrew valve, adjust (while not burning hands on hot boiler), reassemble, and repeat. It took 4 or 5 iterations to get it the way I wanted, I was moving about 1/2 turn of the adjustment nut each time. I think these come from the factory set very high, so I’m guessing you could improve your results just by loosening the nut a turn or two from factory tight. Espresso is now much easer to make (and much better tasting), and with the pressure gauge, I know any problems are my fault, and not the machine’s.

Details of the pressure gauge: I had a friend weld a piece of stainless tubing to a blank filter basket (could probably get this done at a welding shop for $10 and a six pack as well), and attached to a tee, a needle valve, and a liquid-filled pressure gauge. I can adjust the flow to approximate espresso flow rates, and dial in the pressure from there.

I recently purchased an espresso machine to fuel my addiction - a Gaggia Baby circa mid 1990’s. You might wonder why I bought such an old machine, but it was a smoking deal - I got the machine and the grinder for a super-low price, and then sold the grinder on ebay to basically pay for both. So, it was worth it to put some time and a little money into making it like new again.

Gaggia home machines are pretty ubiquitous, as the internals have been the same for 20 years or so, with only cosmetic changes outside - so parts and instructions aren’t too difficult to find. My particular model is a “Baby”, which includes the 3-way valve and an adjustable OPV (over-pressure or pressure relief) valve, otherwise all models are basically the same. Being about 15 years old, it was showing some wear and tear, and was also showing that it hadn’t been cleaned in a LONG time. Before I noticed how much gunk was built up on it, I tried to pull a few shots - they all came out way too quickly, even with the grinder burrs basically touching.

So, I did what I usually do, and took the whole thing apart :). Gaggia machines are very easy to tear down, all it takes is a couple screwdrivers and allen wrenches. When you do take these machines apart, just be sure to label all the wires and take some photos to reference when re-assembling - a little masking tape and a sharpie can go a long way.

Once everything was apart, I started cleaning. The group (part the holds the portafilter) needed a ton of cleaning and scraping, there was years of coffee gunk in there. All parts got a few soaks in descaling solution and citric acid baths, there was quite a bit of scale on everything. It took about 5 soaks to get everything cleaned up, and a bit of scrubbing inside the boiler as well. I purchased a complete Gaggia rebuild kit on ebay from “supercoffeeman”, which includes all seals and gaskets needed to make the machine like new. For an older machine, its safe just to replace everything, for a newer machine all you may need to replace is the group gasket. In any case, if the rubber is brittle or cracked, its time to replace- mine certainly was. In subsequent posts, I’ll go over the details of the mods and adjustments I went through to get it dialed in pefectly…