Blue water after descaling...

#1: Post by **toolate** » June 13th, 2018, 9:24 pm

I see a number of old threads on blue water after desclaing La Pavoni Pro pre Milleniium
I too get blue water when i use Citric acid solution (1tbsp to one liter). It quickly rinses away. The descaling leaves my boiler a brownish color.

Is this the norm?

June 13th, 2018, 9:31 pm

Blue or green water is normal; it may be the reacted acid + scale. Brown boiler is tarnished brass I believe.

#3: Post by **Jabberwocke** » June 15th, 2018, 11:46 am

I dont think color is reaction to dissolve scale. That should be colorless. Blue/green is due to leached copper ions in the water.

#4: Post by **OldNuc** » June 15th, 2018, 2:31 pm

It is also not a good sign and indicates excessive acid cleaning. If the water Ph is very slightly alkaline then the black copper oxide will build up and this is what you should see, completely black interior of a copper boiler.

#5: Post by **hankbates** » June 17th, 2018, 11:45 am

toolate wrote:I see a number of old threads on blue water after desclaing La Pavoni Pro pre Milleniium
I too get blue water when i use Citric acid solution (1tbsp to one liter). It quickly rinses away. The descaling leaves my boiler a brownish color.

Is this the norm?

Blue water denotes attack on the copper in your boiler, which if continued could lead to boiler failure.
Using citric acid could cause plugging of the tube leading to the pressurestat and cause it to stop working. Calcium citrate which is a byproduct of citric acid descaling is much more insoluble than is Calcium acetate. In spite of the need for flushing to remove taste, diluted vinegar is a much friendlier descaler.

#6: Post by **homeburrero** » June 17th, 2018, 1:06 pm

You will see opinions, even from espresso machine vendors that blue-green water after a descale is 'normal.' But as everyone here has said, that color is due to copper compounds dissolved in the water and is not such a good thing because it indicates that you are dissolving (i.e., corroding) your copper boiler, pipes, and/or brass fittings.

If your machine has blue-green deposits inside, then that could be a form of scale, including copper carbonate, and in that case a proper descale would give you a blue or cyan tinge to the descale water. The cause of blue-green deposits is complex, and one possible cause would be the machine having been exposed to water with a high chloride content. Ideally you want to eventually eliminate the blue-green deposits, so that any scale in there is the whitish calcium carbonate limescale, and the descaling solution then becomes nearly colorless. If you have no deposits, then you simply should not descale at all.

As hankbates mentioned, vinegar should be better in this case. Calcium citrate (from citric acid and calcium carbonate) may precipitate and settle in the bottom of the boiler where your pressurestat tube is, potentially causing a hidden clog that prevents the pressurestat from working.

toolate wrote:I see a number of old threads on blue water after desclaing La Pavoni Pro pre Milleniium

0ne of them, with the same title as yours -Blue water after descaling... - is loaded with chemistry background and practical advice from the late Dr. Pavlis. Highly recommended reading on the subject.

#7: Post by **jwCrema** » June 17th, 2018, 11:40 pm

homeburrero wrote: ...0ne of them, with the same title as yours -Blue water after descaling... - is loaded with chemistry background and practical advice from the late Dr. Pavlis. Highly recommended reading on the subject.

A colleague of mine has a Ph.D in inorganic Chemistry. He's not interested in espresso, but he is blown away by our interest in the science we dive into about making espresso. I quizzed him on the topics Dr. Pavlis wrote about in this link without leading the witness.

My colleague gave the exact same advice - it's like I am working with the young Dr Pavlis. I just need to hook him on our hobby and get him to join the site.

#8: Post by **Headala** » June 18th, 2018, 8:03 am

jwCrema wrote:
A colleague of mine has a Ph.D in inorganic Chemistry. He's not interested in espresso, but he is blown away by our interest in the science we dive into about making espresso. I quizzed him on the topics Dr. Pavlis wrote about in this link without leading the witness.

My colleague gave the exact same advice - it's like I am working with the young Dr Pavlis. I just need to hook him on our hobby and get him to join the site.

Start him off with an Affogato

June 18th, 2018, 4:15 pm

Brilliant suggestion - one catch. He's doing the low carb thing right now. Caffe con panna?

#10: Post by **sweaner** » June 18th, 2018, 10:25 pm

I have been of the opinion that some blue water is a normal event if descaling with acetic or citric acid. I am not thinking that one could "dissolve" the boiler with gentle descaling periodically.

Maybe I will try to dissolve a penny!