1977 La Pavoni Europiccola with green deposits/scale

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.
summer

#1: Post by summer »

Hi all, I recently found a 1977 Europiccola.
While it is in very good condition, there is a couple of issues I would like you guys to comment on.



1) Green deposits on the lip part between the group and the boiler. The machine had some scale, also present in the group.
Is the green deposits scale related? How to approach?


2) Green deposits at the element. It does look like a small leak at the element to me, but not a major leak considering its 38 years old... Leave it like it is, or repair the elements?

Thanks for the help!

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rpavlis

#2: Post by rpavlis »

I have a nearly identical machine, except it is 1978 and has a different type of switch. Mine is the "fake" brass and copper model.

Green deposits almost always mean copper compounds, possibly copper carbonate, though there are other things it could be such as Cu₂(OH)₃Cl. Deposits of copper compounds are, to my mind, not good. That means copper from the boiler has reacted to make these compounds! These things will generally dissolve in weak acid solutions. Probably regular white household vinegar is best, because essentially all acetates are soluble. You can always remove acetic acid residues with water rinses.

What do you see when you look into the boiler with the cap removed? These have the old "lipless" boilers by the way. What is the appearance of the heating elements? One way to get green deposits is to use hard water with high chloride. When you descale with white vinegar you may see a bluish solution. If you see a greenish solution it probably means a LOT of chloride. Cu₂(OH)₃Cl would produce a green colour when dissolved.

You do not want copper compounds and chloride around, because the two together can create a nasty corrosion situation, especially in acidic conditions. I would try to get rid of the green deposits with vinegar strength acetic acid, then I would dissolve some sodium carbonate or bicarbonate in water and wash the area with that. That will tend to get rid of chlorides. Then rise with lots of water.

I suspect the machine was used with high chloride content water. Be sure that the water you use is very low in chlorides. I have long advocated using 0.5 to 1.0 mM (50-100mg/litre) potassium bicarbonate dissolved in distilled water for espresso brewing because it keeps the pH of the brew water correct, and you ultimately get virtually identical espresso to that produced by slightly to medium "hard" water. (Ca and Mg are present in much higher quantity in the beans than in the hardest water by the way.)

One more thing, these early generation 2 machines have two holes to admit water to the space below the piston. This, to me, admits water MUCH too fast. I took the inlet tube and tapped it with an M7 tap, and then took a short piece of 7mm brass rod, bored a 1.8 to 2.0 mm hole in it and used a die to cut M7 threads on it. I screwed this into the end of the inlet tube, this reduces the flow rate to approximately what later generation 2 machines have.

When you have the deposits removed you can check to find out if there be any leaks. You need to remove green deposits, because they can catalyse serious corrosion. My 1978 had green deposits all over the inlet tube. When I removed them with dilute acid its surface was pitted and the acid solution was strongly blue.

summer (original poster)

#3: Post by summer (original poster) »

rpavlis wrote:What do you see when you look into the boiler with the cap removed? These have the old "lipless" boilers by the way. What is the appearance of the heating elements? One way to get green deposits is to use hard water with high chloride. When you descale with white vinegar you may see a bluish solution. If you see a greenish solution it probably means a LOT of chloride. Cu₂(OH)₃Cl would produce a green colour when dissolved.
Thank you for helping!
Regarding water used: This machine has been used by one owner only, and I strongly think he used the tapwater (but I'm not sure).
Analysis of the tapwater in his area reads klorid (Cl) 21 mg/L and hardness 12.2 dH - I dont know if its a high chloride, but the water is pretty hard. More analysis here (in Danish): http://www.analytech-online.dk/2693/Analyses/81/9495

The first thing I did, was a fast descaling with citric acid (1 tablesp./1liter) - the water came out bluish.
There might be a slight sheen of green on the elements, its almost gone now after the descale/water-rinse - it could also just be the sheen of a thin layer of scale...I only notice it now I look for it. You can see it best in the second picture.
The end of the tube shows the same kind of green sheen, but the green is nowhere as strong as on the group.
The other colors in the boiler is red/brown, black and golden.
:roll: I have no pics of the boiler before the descaling, but here are some photos after descale.





As you see, the dippertube was mounted so close to the element, that they created a small 'scale-formation' (that actually plugged the tube) and there is some black stuff on the element around the remaining scale.
Does your tube end this close to the element? I think about gently bending my tube, so it does not end on top of the elements...
rpavlis wrote:One more thing, these early generation 2 machines have two holes to admit water to the space below the piston. This, to me, admits water MUCH too fast. I took the inlet tube and tapped it with an M7 tap, and then took a short piece of 7mm brass rod, bored a 1.8 to 2.0 mm hole in it and used a die to cut M7 threads on it. I screwed this into the end of the inlet tube, this reduces the flow rate to approximately what later generation 2 machines have.
Wow, thank you for the tip. I'll try without first, and might try the restrictor if I get problems with the flow.
Thank you!

User avatar
rpavlis

#4: Post by rpavlis »

During today's 48 km bicycle ride I thought of the problem with the green scale. Since this is an old 1977 La Pavoni machine replacements are very difficult to find or fabricate.

You can probably obtain pure distilled water in a grocery store, I suspect you can probably find 4 or 5 litre jugs of it for perhaps €1.25 or so. This is enough to make a lot of espresso. Straight distilled water tends to make sour espresso. Contrary to what some will tell you, however, it is not corrosive. However oxide coats on copper and its alloys are more stable with slightly alkaline water, and that protects copper from air. I personally use, as I have stated many times, about 0.5 to 1.0 mMolar potassium bicarbonate. You can simply add from 250 to 500 milligrams of potassium bicarbonate to a 5 litre container. You can use sodium bicarbonate too, but I do not like doing that because it seems to create peculiar flavours because Na is very low in coffee beans. You would use less of it perhaps 150 to 300 mg in 5 litres. If you used such water the deposits would all go away and more would not form. The copper would develop a very impervious coat of CuO. There would never be a need to descale. Water composition would not change during a session from separation of bicarbonates in the boiler. I noticed that there was some sulphate in your water analysis. Perhaps some of the scale is calcium sulphate. This will slowly go away with just potassium bicarbonate in the water. You will also not have problems from microorganisms getting into the brew water and making nasty tasting things like 2-methylisoborneol.

summer (original poster)

#5: Post by summer (original poster) »

Hi again, I'll definitely try the distilled water (and white vinegar instead of citric acid) - and its nice to have a plan that gets rid of the green stuff.
(BTW - In my levers, I always have used a bottled mineral water with values as close as possible to the SCAA recommendations.)

Last question: My dippertube ends very close to the element (as you see in the photo). Is yours constructed the same way?

Thank you so much for the help! :D

User avatar
rpavlis

#6: Post by rpavlis »

I just looked into the 1978, the dipper tube ends perhaps 5mm above the element.

If you put bicarbonate into distilled water the taste will be very similar to using water in which the bicarbonate comes from hard water, but it will not produce scale. Any scale insoluble in dilute weak acid generally will gradually disappear. Adding bicarbonate to distilled water instead of depending on natural water lets you set the bicarbonate level, and you will have another variable completely under control. The darker the roast is, the less bicarbonate one needs for the ideal cup. Remember again, that there is far more Ca and Mg in the beans than in hard water.