This is a great introduction to water issues, some of which is more than introductory. Takeaway: plain R.O./distilled water sucks for coffee because it doesn't have enough alkalinity to get "the tasty nuggets" out. This is a Scott Guglielmino presentation from an LM "Out of the Box" program. Some of you will have already seen this in person.

Thank you for sharing this. This was the focus of their stateside tour last year. I think it added a lot more value to the whole dialogue of espresso preparation than debating temp stability or pressure profiling could.

No doubt there was some good practical suggestions in the talk, but the chemistry was scary bad.

. . . but the chemistry was scary bad.

I don't quite know what you mean by this but you would do us all a big favor by sending Scott G. an email with your critique. The very fact that he (and LM) is emphasizing the necessity of water quality is a huge plus for us all.

I have not yet watched the entire video - much thanks Marshall - but the initial minutes where his PP slides discussed "tasty coffee" and "healthy machines" are/should be subjects we need to be familiar with.

asicign wrote:No doubt there was some good practical suggestions in the talk, but the chemistry was scary bad.

Only 6 minutes in and there's two glaring errors. I wonder if this was the case with each presentation? I had only heard about barista's experiences with the tour. I think he was just nervous.

The more hydrogen ≠ pH going up

Permanent hardness ≠ stuff carried off by steam. Permanent hardness is the hardness that is not removed by boiling.

There are some seriously wrong ideas presented in this video!

One of the worst is the concept that calcium and/or magnesium carbonate scale protects underlying metals. That is seriously WRONG, for almost all metals. Metals commonly used in espresso machines stainless, brass, bronze, etc. react with air and form impervious OXIDE coats of the metal involved. Anything that creates an impervious and NON porous microscopically thin layer of oxide will stabilise metals, and anything that dissolves such layers will enhance corrosion. Transition metal oxides are generally very insoluble in pure water. As this video correctly says, chloride (he seems to have chloride and chlorine confused), is bad. It is bad because chloride forms strong complexes with many metals. This removes the protective coat. With copper it may also form CuCl which is the catalyst for a process similar to iron rusting. Pure iron does NOT form a stable impervious coat, and ferrous iron is catalytic for oxidaion of iron--iron can soon end up a pile of rust.

Descaling a machine introduces acids, the higher H+ concentration we get from that the more the oxide coats get removed. When new coating forms the metal involved gets thinner.

For copper and copper alloys the oxide coatings are most stable in slightly alkaline water that does not contain chloride. Most other metals that form oxide coats follow similar behaviour. Note that aluminium is so reactive that, even though it forms a stable oxide coat, it can corrode very badly, especially when in constant contact with water.

Traces of phosphate form insoluble phosphate coats on some metals. It is thus a corrosion inhibitor for these metals.

Calcium carbonate scale can result in corrosion. One can tell when serious corrosion has occurred if one descale something and find the solution is blue! That blue is dissolved Cu2+!!!

He is indeed right that small amounts of bicarbonate reduce corrosion--because its alkalinity maintains a very weakly alkaline environment where many metal oxides are most stable.

He does not seem to understand the concept of ionic strength. When ionic materials are dissolved in water they reduce the solubility of non-ionic materials unless the ionic materials react with the material being dissolved. It does not matter if it be Na, K, Rb, Ca, Sr, Mg or any other ion the result will be about the same. It is amazing that if one add potassium carbonate to distilled alcoholic beverages, one can raise the ionic strength in the water to levels so high that not even ethanol will dissolve in the water! The alcohol will separate from the water!

The presence of bicarbonate ion in water can have a profound effect on flavour. It is amphoteric--reacting with both acids and bases. It also acts as a buffer to maintain specific activities of H3O+ and OH- ions. When it is absent, the massive amount of materials in the coffee grounds set the H30+ and OH- activities, relatively small amounts of bicarbonate will result in keeping the activities of these materials about the same.

If one take distilled water and put about 70 to 120 mg/litre of NaHCO3 into it, with perhaps 10 to 20 mg/litre of a sodium or potassium phosphate one will probably have about the least corrosive environment possible. No carbonate scale will form, and there is nothing to mess up the oxide coats. (One could also use KHCO3).

By the way coffee grounds contain massive amounts of K, along with substantial Mg and Ca. It is quite poor in Na. Some coffee actually contains more Rb and Na!!!!!

Coffee contains at least three mercaptans in low concentration. These contribute strongly to the flavour of coffee. Roasted coffee contains only traces of these materials, they have very bad odours in higher concentration. Mercaptans are more soluble in weakly alkaline water than neutral, so their extraction is enhanced by bicarbonate ion. The same is true of some trace phenols and other weak acid.

Another thing that he did not discuss is that sulphate in Ca contaminated water is VERY VERY bad when used for steaming. CaSO4 is insoluble in water, and it only dissolves in nasty special descalers--that also are certain to begin dissolving boiler walls!

rpavlis wrote:One of the worst is the concept that calcium and/or magnesium carbonate scale protects underlying metals. That is seriously WRONG, for almost all metals. Metals commonly used in espresso machines stainless, brass, bronze, etc. react with air and form impervious OXIDE coats of the metal involved. Anything that creates an impervious and NON porous microscopically thin layer of oxide will stabilise metals, and anything that dissolves such layers will enhance corrosion.

I asked me wife about this, since she spent many years in industrial water treatment as a chemist. She said Scott was correct. A thin layer of calcium carbonate is desirable, as it protects the metals. Oxide coatings are not, as they continue to attack the metal and thin it out.

No way is that correct. Oxide coatings MUST be preserved, and anything that disturb them is damaging. Look at the carbonate it is porous. On brass calcium carbonate deposits are often green from cupric carbonate. Every descaling is removes oxide coats and gets boilers thinner and thinner.