homeburrero wrote:High bicarbonate should also tend to decrease the flow rate

That's very interesting. What causes that? It suggests that careless bicarb measurement, which I've been guilty of, would outweigh grind adjustments!

homeburrero wrote:High bicarbonate should also tend to decrease the flow rate,...

BobStern wrote:That's very interesting. What causes that? It suggests that careless bicarb measurement, which I've been guilty of, would outweigh grind adjustments!

One oft-referenced study was Fond, O. (1995). Effect of water and coffee acidity on extraction. Dynamics of coffee bed compaction in Espresso type extraction, ASIC 16th International Scientific Colloquium on Coffee (pp. 413-421). Kyoto, Japan. That study looked at very hard water, demineralized water, softened water, and water with added bicarbonate. The postulated cause was that the bicarbonate caused CO2 release and more swelling and compaction during the wetting phase, but I think the jury's still out on what the mechanism might be. Slower extraction times with high bicarbonate water when making drip coffee has been observed for a long time.

After my last post I stumbled upon a more complete resource for espresso crema science -- a review article by Illy and Navarini, Neglected Food Bubbles: The Espresso Coffee Foam, which is freely available (thanks to PubMed Central) : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3140933/

Thanks for the reply homeburrero!

Could you explain this part to me...

homeburrero wrote:Downside is that the system will require that the hardness source be non-carbonate salts like sulfate or chloride which could be undesirable if the final blend's hardness is set high and the alkalinity is set low.

Why would the system require the source to be non-carbonate salts and why would that be undesirable?

Thanks

jdsuz wrote:Could you explain this part to me ... Why would the system require the source to be non-carbonate salts and why would that be undesirable?

This was in the context of a proposed liquid injector system. Calcium and magnesium carbonates are not very soluble, so you can't make a concentrated liquid solution of them to use in an injector. The alternative soluble forms of Ca and Mg would be chlorides like calcium chloride or sulfates like magnesium sulfate. Chlorides and to a lesser degree sulfates are associated with corrosion problems. For example, La Marzocco's water advice recommends that chloride be below 30 mg/L. They at one time also advised that sulfate be below 50 mg/L. Pentair/Claris recommends that chloride be below 80 mg/L and sulfate below 150 mg/L if using their de-carbonization softener cartridge.

Typical systems that do remineralize with calcium and magnesium carbonates use cartridges loaded with solid minerals.

Thanks! That makes a lot of sense. Perhaps just adding the carbonate as mentioned earlier in this thread may be the way to go? One last question.. my pH is sitting at 8.8. According to the LSI I cant increase my carbonates past 20 or 30ppm without causing scale. Is there a good, safe way to reduce the pH either by adding something to the concentrate or adding another bit of equipment? Im no chemist so im apprehensive when dealing with acids and pH levels.

So I'm really not doing much good using epsom salt in my water recipe for my ecm classika... here I was thinking I'm helping with scaling.

Yeh I have the exact same thought. And honestly I'm totally confused now whether it's a problem or not or if I should switch to something other than epsom.

Given the recent discussion, I want to try the KHCO3 recipe.

How much KHCO3 in powder form would one need to add to a gallon of distilled H2O?

First off I am not a chemist but this is what I can gather from my research on this site.

My new machine will hopefully be arriving soon and I plan to try this also to preclude scaling and hopefully have a good taste. From the reading I have done about rpavlis mixtures of potassium bicarbonate with distilled water I think these are the right ratios:

For light roast coffees, 0.4gr./gal

For medium roasts, 0.3gr./gal

For dark roasts, 0.2gr./gal

If these are the wrong ratios, one of the water gurus will soon be here to correct me and I would be glad to know the proper numbers also.

If these ratios are correct my intention for a medium roast would be to put 3 gr. of pot bicarb into 100 ml of water and mix thoroughly then put 10 ml. of that solution into 1 gal. of distilled water. This would be done to make the quantities more manageable on non lab grade 0.1gr. digital scales.

Also if these are close enough for arguments sake 100ml. water weighs very close to 100gr. so 10.3gr. of the solution/gal. should work out close enough for my usage.

sweaner wrote:How much KHCO3 in powder form would one need to add to a gallon of distilled H2O?

The 1 millimole/liter [KHCO3] works out to 0.38 grams of KHCO3 in a US gallon of water. That would give you an alkalinity value of 50 mg/L CaCO3 equivalent and a total hardness of zero.

It's impractical to weigh out that small an amount so most folks make a concentrate. For example, you could put 97g of KHCO3 powder in a gallon of pure water, shake it well and it will dissolve, then when making your coffee water add just a tablespoon of that concentrate to each gallon of purified water. You could experiment with using less, maybe half that amount of the concentrate. (Professor Pavlis says he uses 0.5 to 1.0 millimole/L in his machines:

rpavlis wrote: [ in 1977 La Pavoni Europiccola with green deposits/scale ] ...
I personally use, as I have stated many times, about 0.5 to 1.0 mMolar potassium bicarbonate.

check my work:
given 3.8 liters in a gallon of water,
100 grams in a mole of KHCO3
1000 millimoles in a mole
3.8 * 100 / 1000 = 0.38 g/gallon

given 256 US tablespoons in a US gallon
97 grams/gal / 256 dilution factor = 0.38 g/gallon

Edit Addition: Posted this while bettysnephew was posting his. Good to see that our calculations agree.