Descaling La Pavoni - Problems

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RHP

#1: Post by RHP »

Hi!

I am trying to descale my La Pavoni for the first time... when it arrived it had no scale in and had hardly been used, so I've somewhat put off descaling it. I've had it well over a year... safe to say, I will try and be more frequent with my descaling from now on so it is easier to maintain.

My procedure is:

1) Fill tank with water
2) Add descaler, as described by manufacturer (I'm using Oust)
3) Turn on La Pavoni but not quite to boil point, just before, then turn off.
4) Leave 30 minutes.
5) Empty, and rinse
6) Carefully noting not to push the water / descaler through the machine. I am just adding into the tank then emptying out by turning it upside down.

My two issues are:

1) A very small amount of scale is removed. I'd say maybe 10%. Poking with a chop stick (technical tool), the scale does seem very soft so I'm not sure what it's not coming off. Do I need to repeat more times and just keep going? Or let it soak for longer?
2) I have noticed the small pipe that goes from tank into the lever head area has gone a light brown-red sort of colour since doing a cycle with the descaler. I do not know what this pipe is made of... but should I be concerned? They shouldn't be using a plain mild steel in here that would rust?

If you had a moment to share your experience / what you think might be the issue/solution, it would be greatly appreciated!

Thanks,
Richard (UK)

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trapperkeeper

#2: Post by trapperkeeper »

a quick search will reveal that citric acid or white vinegar will work and are mild enough not to cause damage. Prefer citric acid as heated vinegar smells! Citric acid is available in the canning section of a supermarket - it is very inexpensive. Mix 1-2 tablespoons per liter of hot water and fill the boiler with it. You can heat the machine if you want, but usually hot water is sufficient. Leave for 30 min and see how it goes. The liquid will turn blue/green - that's ok. Rinse well with water. I've done this myself a few times and it worked well for me.
LMWDP #600

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MB

#3: Post by MB »

The brownish red pipe is copper. [EDIT: I stand corrected, see below.]
LMWDP #472

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homeburrero
Team HB

#4: Post by homeburrero »

FWIW I'll offer some contrasting opinions . . .

I'm pretty sure that Pavoni siphon tubes are threaded at the top and are made of brass (a copper alloy.) After an acid soak they may look even pinkish because the copper oxide layer and some of the zinc is removed from the surface. You can give them a polishing and they'll look more brassy, but it's fine to just let them oxidize back to the dark dull copper oxide color - copper oxide is a healthy protective layer.

On this machine, vinegar has an advantage over citric acid. Vinegar will dissolve carbonate scale to highly soluble calcium acetate, whereas citric acid will dissolve it to calcium citrate, which in theory may remain and clog small passageways like that pressurestat tube at the bottom of the boiler. (This is all based on home-barista posts like this one, by rpavlis, the late Robert Pavlis - chemistry professor and La Pavoni enthusiast.) Also, if you are soaking chrome plated parts, vinegar is a little kinder to chrome than citric acid. But you will need to spend more time rinsing to get rid of the vinegar taste and odor.

It's debatable as to whether blue/green water after a descale is OK. If you have blue/green deposits in your machine, then you will expect unavoidable blue/green in the water as those deposits dissolve. But be aware that blue/green in the water is an indication of dissolved copper, and ideally you don't want to be dissolving and removing much copper - it may be a sign that you are descaling too harshly and/or too often.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

RHP

#5: Post by RHP »

trapperkeeper wrote:a quick search will reveal that citric acid or white vinegar will work and are mild enough not to cause damage. Prefer citric acid as heated vinegar smells! Citric acid is available in the canning section of a supermarket - it is very inexpensive. Mix 1-2 tablespoons per liter of hot water and fill the boiler with it. You can heat the machine if you want, but usually hot water is sufficient. Leave for 30 min and see how it goes. The liquid will turn blue/green - that's ok. Rinse well with water. I've done this myself a few times and it worked well for me.
Thanks! My process is very similar, as above. I'm also using a citric acid based descaler, but it just doesn't seem to be eating through properly...

RHP

#6: Post by RHP »

MB wrote:The brownish red pipe is copper. [EDIT: I stand corrected, see below.]
Well brass is mostly copper so it's the same idea. Thanks!
homeburrero wrote:FWIW I'll offer some contrasting opinions . . .

I'm pretty sure that Pavoni siphon tubes are threaded at the top and are made of brass (a copper alloy.) After an acid soak they may look even pinkish because the copper oxide layer and some of the zinc is removed from the surface. You can give them a polishing and they'll look more brassy, but it's fine to just let them oxidize back to the dark dull copper oxide color - copper oxide is a healthy protective layer.

On this machine, vinegar has an advantage over citric acid. Vinegar will dissolve carbonate scale to highly soluble calcium acetate, whereas citric acid will dissolve it to calcium citrate, which in theory may remain and clog small passageways like that pressurestat tube at the bottom of the boiler. (This is all based on home-barista posts like this one, by rpavlis, the late Robert Pavlis - chemistry professor and La Pavoni enthusiast.) Also, if you are soaking chrome plated parts, vinegar is a little kinder to chrome than citric acid. But you will need to spend more time rinsing to get rid of the vinegar taste and odor.

It's debatable as to whether blue/green water after a descale is OK. If you have blue/green deposits in your machine, then you will expect unavoidable blue/green in the water as those deposits dissolve. But be aware that blue/green in the water is an indication of dissolved copper, and ideally you don't want to be dissolving and removing much copper - it may be a sign that you are descaling too harshly and/or too often.
Thanks for sharing all of that, it is appreciated.

I've certainly got no problem with doing more rinses for vinegar descaling instead (I do have other ways of making coffee here)... so I'll certainly try this next time, I had no idea it was more effective at breaking down the scale into water soluble form.

I did note on the last soaking - which was for 2 hours or so - that the water came out with a very light green tinge. This has to be the first descaling in 2 years probably, so I doubt I am doing it too often, but will try the vinegar method next time and just try and use less acid / keep it up to maintenance so I don't have to be as "harsh" with it next time around.

After a much longer soak, I think I'm getting there. It's all pretty much gone from the outside of the boiler and has started crumbling off the heating coil more so. There is just a thicker "bed" of it at the bottom, and a lot still around the coil, so I've just filled it up to this level and then I'm going to soak it again. Hopefully that'll sort it out.

I guess I'm just surprised by how long / how many attempts this has taken compared to what I've read in research. This is my 4-5th soaking now and there is still significant scale in there...

MCALheaven

#7: Post by MCALheaven »

My best descaling is 25% plain vinegar mixed with 75% water, heated to at least 180F for 1 hour. Continuous heat is the secret. This will dissolve most scale unless its extremely heavy, in which case repeat as needed. Two complete rinses with water removes all vinegar smell.

RHP

#8: Post by RHP » replying to MCALheaven »

Thank you sir! Going to try this tomorrow or Sunday. I estimate I've had descaler in there for 15 hours now in different batches and there is still stubborn scale on there. Whatever I'm using obviously isn't cutting it...

I assume you're using plain, white vinegar? Usually around 2%? Not malt vinegar or anything you'd cook with?

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homeburrero
Team HB

#9: Post by homeburrero »

I believe plain white vinegar is typically 5-6% acetic acid (appx 0.8 molar). Dr. Pavlis said he diluted white vinegar to 50:50. On tough jobs he might descale repeatedly, with less than 1 hour soaks. For helping to dissolve scale in the pressurestat pipe he would cycle the machine up to pressure a few times - see this post: La Pavoni Europiccola not heating
RHP wrote:I estimate I've had descaler in there for 15 hours now in different batches and there is still stubborn scale on there. Whatever I'm using obviously isn't cutting it...
That makes me think it's not carbonate scale, which should have dissolved in that Oust (citric acid*) descaler. I wonder if maybe you're dealing with calcium sulfate scale, or even worse, silica. One way of dealing with that is to start using very clean, soft water that has no sulfate or silica, and let that white stuff slowly dissolve as you use the machine. Here's some discussion about that: The chemistry of scale in espresso machine boilers [FAQ].

*Edit addition: The liquid 'all-purpose' Oust descaler is, according to the MSDS, lactic acid rather than citric acid.
Pat
nínádiishʼnahgo gohwééh náshdlį́į́h

MCALheaven

#10: Post by MCALheaven »

Yes, plain vinegar, 5% acid. Continuous heat for an hour is the secret. Water/vinegar mixture that is allowed to cool (as in turning off the machine) will take many, many hours and not do as good a job. In fact, only because of continuous heat will 25/75 vinegar water work. Without the heat, it's no good. Very safe levels of acid this way, IMO. 50/50 vinegar water is only needed when not enough continuous heat is applied in my experience. Not an expert, but I have plenty of practice descaling water distillers and I can guarantee you this works as well or better than any descaling product I've tried. Good luck to you.