homeburrero wrote:Sorry I'm so slow to respond here. I'm enjoying this thread, but it covers a lot of territory so I put off replies until I found some extra time. My reply did end up long and pretty geeky.
Don't be sorry. I was surprised, not to mention grateful, that you responded so quickly on Sunday; quality over speed is fine. I doubt you will manage to write an entry that is too long or too geeky for my taste---as this thread probably demonstrates. I do feel a bit as if I'm trying to swallow the whole cow at once.
homeburrero wrote:Yes, all of his posts are informative and often fun, especially if you enjoy recalling a little high school physics and chemistry.
I have had to relearn and learn a lot of chemistry for my job. It's pretty neat when well explained, which he did.
homeburrero wrote:Re cupping, keep in mind that espresso is far more tolerant of alkalinity than cupping or pourover coffee.
Great timing, I'm doing some cupping today. Absolutely the buffer will remove acidity, that's its "job." I will vary alkalinity and hope to taste its effects.
homeburrero wrote:Speaking of Marco Wellinger, he's an author of some excellent coffee water references
That's funny, I used to live in Wädenswil, although I never visited his institute. Of course, at the time I drank Nespresso. . .
Reading that chapter will be enjoyable, and if it resonates I might just get the WQ Handbook. I like different kinds of coffee preparation, and water quality is far too easily underestimated.
homeburrero wrote:Here's a thread that describes my coffee recipe. . . . I just use a concentrate that has lots of undissolved calcium carbonate. i shake it well before pouring out a shot to spike my coffee water.
Agitation will distribute the particles in suspension, but if the calcium carbonate remains undissolved, surely it isn't helpful? As far as I (don't) understand, if the water is basic due to the added carbonates, CaCO3 and MgCO3 are only soluble in small amounts. I suppose the reason for keeping a distribution of particles in suspension is to maintain the max amounts of Ca and Mg cation concentrations that will go into solution from the particles. (That would explain why you don't offer their concentrations.) Wikipedia says the solubility of CaCO3 in water is 13 mg/l at 25°C, and of MgCO3 is 139 mg/l at 25°C and 60 mg/l at 100°C. Both compounds have increased solubility with increased pressure of CO2 in water, which I suppose is relevant in the boiler.
I have a friend who is a professor of chemistry at an institute in Germany, and we had a long talk the other night about espresso-machine water chemistry. It's safe to say any problems with what I report from that are down to mistakes in my understanding and memory. My main question was about a possible source of MgCO3. The options I have available at the online store where I have ordered the compounds (they have pharmacy quality) are:
Composition: approximately 4MgCO3.Mg (OH) 2.xH2O
MgO 40 to 45%
Mg 27 to 30%
Composition: approximately 4MgCO3.Mg (OH) 2.xH2O. The substance is not clearly defined. The MgCO3 / Mg (OH) 2 ratio varies. Therefore, the MgO content determined by analysis is important.
There is another option, but it contains a mix of CaCO3 and MgCO3 (dolomite), and I would prefer to add them individually. The above options have a large amount of MgO, and I wanted to understand whether it might dissolve in the water. He said it wouldn't, basically it forms a stable layer of (I think) magnesium hydroxide on the lattice surface as described here
, and so the lattice stays intact. I suppose if the MgO is stable I could go with option 1 and work with the proportion of MgCO3 + Mg hydroxide. I'd rather find a decent source of MgCO3, but after some web-search grinding, Bulk Supplements is the only thing that came up as available. Shipping is pretty steep for me. Maybe none of it matters if the Mg concentrate will just saturate?
My understanding is that sulfate is far less a corrosion problem than chloride, maybe half as corrosive when it comes to stainless steel. So at these Perger recipe levels and with good alkalinity sulfate is probably a minor corrosion concern. Sulfate has been reported as having a laxative effect, but that would not happen at these concentrations. In combination with calcium ions, sulfate can be a concern because of calcium sulfate scale. . . .
Compared to sulfate, chloride is much worse for corrosion in stainless and especially bad for copper and copper alloys. R Pavlis discussed it often, including this post: Elektra Microcasa a Leva boiler leak problem
I asked my friend about sulfate corrosion in order to get a sense of acceptable concentrations, and he did a quick
browse of the literature (he has access to paid databases), but didn't find articles that provided obvious insights. I definitely am not mixing sulphate with Ca. I had read the Elektra Microcasa thread, but looking at it again I had a good laugh about him writing, "I hate to sound professorial again, but I think I should explain the chloride problem." Perfect!
The boilers in my machine are stainless steel; I don't yet know whether any of the pipes are copper. Probably should ask Lelit. Since there were chlorides in the water for my first month of machine use, I wonder whether there are similarities in the corrosion mechanism for stainless steel as for Cu. If the chlorine atoms bond with the metal and stay in the structure as described for copper, I wouldn't be able to get rid of them just by no switching to water without chloride. I'm not worried about it, since the amount of any deposited Cl contaminants is probably pretty small.
homeburrero wrote:I can'/t say that I understand it [solubility of MgCO3 vs CaCO3 at high temp] either, and there are conflicting reports The chemistry is different, especially at high pH, where it decomposes to Mg(OH)2 rather than MgCO2.
My professor friend also didn't have an ready resources to help analyze and quantify the behavior.
homeburrero wrote:The chloride limits are for chloride as ion, so your number for comparison would be 52.5 mg/L chloride as ion. When reading water reports, the chloride number is also usually reported as mg'L of the ion, not in CaCO3 chemical equivalents. But still, that number is not good.
Should be near zero now, as I've switched to rpavlis water. I'm only concerned about chloride if I go with a filter; more on this below.
homeburrero wrote:That is an odd method. To calculate a TDS of a water in a recipe you simply need to sum the masses of the minerals that you add minus any of that mass that was due to hydrates. Done that way you come up with about 210 mg/L for your TDS. As you said, for the purposes of LSI it doesn't mater much.
It does seem odd, but I kept running across it in several resources:
Determining the Salinity of Groundwater for Regulatory Purposes in Alberta
2012 TOTAL DISSOLVED SOLIDS RESULTS - LABORATORY CALCULATION DISCREPANCY
Online lecture notes
An online homework assignment
might give insight:
Nicholas Utting wrote:The principal difference between measured and calculated TDS is the loss of CO2 from the bicarbonate (alkalinity) by drying as roughly half only will remain to form calcium and magnesium carbonate
I wonder if this isn't the reason for reformulating carbonates and bicarbonates as CaCO3 equivalents with a 0.6 factor.
homeburrero wrote:That's true. You may see seasonal changes as well as surprise changes caused by the water utility shifting sources. If you can get good analysis reports from your utility it will often show quarterly analysis, or may show range and average values over a year of testing.
This is my current dilemma: should I buy a distiller or a filter system? Yesterday I was on the verge of buying a distiller, but in addition to its size and noise, a distiller uses at least 3 kWh of electric energy to distill 4 liters. Not exactly ecologically or economically attractive. A filter system would be cheaper, more convenient and possibly more ecological, but as noted this requires testing and some analysis of the incoming water with its seasonal variations.
I've tried to do my homework on this, and ended googling with Czech terms. The following link is the online resource for reporting of water quality for Prague. The good news is the numbers are published on a monthly basis, the bad news is that it's only in Czech.
https://www.pvk.cz/vse-o-vode/pitna-vod ... lita-vody/
They provide 106 distinct measurements/evaluations, everything from bacteria to heavy elements to pH and many things I've never heard of, but nothing about carbonates or alkalinity. I translated all entries and isolated the variables I though might be the most interesting. I'm leaving the Czech in with translation, in case anyone reading this wants to check it out the values directly. I will provide a translation of all 106 entries on request, as they would take up a lot of space here. The records lined on the above page currently go back to October 2019.
Nr. index units
č. ukazatel jednotky hyg. limit Oct-19 Nov-19 Dec-19 Jan-20 Feb-20 Mar-20
23 dusičnany nitrates mg/l 50.0 19.4 19.9 18.9 19.0 18.8 18.2
24 dusitany nitrites mg/l 0.50 0.01 0.01 0.01 0.01 0.01 0.01
26 fluoridy fluorides mg/l 1.50 0.11 0.11 0.11 0.13 0.12 0.11
28 hořčík magnesium mg/l 20-30 7.5 7.6 7.4 7.5 7.7 7.3
30 chlor volný free chlorine mg/l 0.30 0.06 0.06 0.06 0.06 0.06 0.07
33 chloridy chlorides mg/l 100.0 26.2 26 26.5 26.1 26.1 26.1
38 konduktivita conductivity mS/m 125.0 41.7 40.3 42.8 40.7 39.3 41.4
44 olovo lead µg/l 10 0.5 0.5 0.5 < 1 < 1 < 1
49 pH - reakce vody pH - water reaction - 6.5-9.5 7.66 7.72 7.64 7.64 7.68 7.63
53 síraný sulphates mg/l 250.0 48 46.7 49.3 48.9 48.9 52
54 sodík sodium mg/l 200.0 14.4 14.9 14.5 14.5 14.7 14.1
56 teplota vody water temperature °C 8-12 11.6 10.8 10.5 9.2 8.3 7.7
62 vápník calcium mg/l 40-80 50.8 46.9 53.9 49.2 47.7 49.6
63 vápník a hořčík Ca and Mg mmol/l 2-3.5 1.58 1.49 1.65 1.53 1.5 1.54
65 železo iron mg/l 0.20 0.03 0.03 0.02 0.04 0.04 0.03
suma chlorečnany sum of chlorates µg/l 200 13.6 15.64 13.64 16.274 18.118 18.056
+ chloritany + chlorites
"Samples are taken from the distribution network in Prague andPodolí, Želivka and Káraný water treatment plants."
"This is the average water quality in Prague. In individual localities of Prague, it may differ according to the type of water supplied (Želivka, Káraný, Želivka + Káraný mixture)."
The Prague area gets the most attention in all of the Czech Republic, and it seems that the values are fairly consistent from month to month, at least from fall to spring. As stated, this is average water quality. The site also maps 2018 averages
in iron, hardness, pH, nitrates and chlorine in the city. Where I live, the hardness and chlorine (not chloride) were lowest and the pH was 7.5-8.5. (There is also a notice in red as to why they have not raised the chlorine levels due to COVID-19.)
The water does taste clean, but in my opinion it has that "chlorine" feel. I don't really know how to evaluate it, but the sulfates and chloride levels seem high enough to cause me hesitation, if the filter system would not filter them. So my main question: Since the BWT Bestmax I was considering "drops alkalinity in addition to hardness and may acidify the water, which is not good if you have chloride or sulfate concerns," is there an alternative filter system that would also filter the chlorides and sulphates?
"It is best always to clean espresso machines after use and wipe them dry. Watch out for rust!"