sbenyo wrote:If taste is not an issue, is the rpavlis completely safe to the machine and is the recommended formula?

Yes, the idea behind the rpavlis water is that it has nothing (no chloride, sulfate, etc.) that might cause corrosion, and nothing (calcium, magnesium, silica, etc.) that might cause scale or similar deposits. And has good alkalinity for corrosion protection but not so much that it might dull the acidity/brightness of an espresso. And if you use potassium bicarbonate you aren't adding any sodium at all. Since coffee is already loaded with potassium the relatively tiny amount of potassium in the water should have no affect on taste. So it's a recipe for ideal machine health but also tweaked for good taste.

sbenyo wrote:Is there any advantage using a formula that has both alkalinity/buffer and hardness (Mg)? Something like this:
https://jayarrcoffee.com/blogs/news/a-g ... king-soda/

There are people who believe that you need hardness minerals (calcium and/or magnesium) for optimal taste. Extraction and taste experiments have not clearly demonstrated to what extent that might be true, and it probably depends on the coffee being brewed. The Jayarr Coffee recipe above would give you water with magnesium hardness of 80 mg/L CaCO3 equivalent, alkalinity of 40 mg/L CaCO3 equivalent, and sulfate ion of 77 mg/L. (To see that in context of other waters' hardness/alkalinity you can refer to this chart.) It's advised for brewed coffee, but you could probably use it in an espresso machine without scaling issues because it has no calcium at all.

P.S.
Lots of folks who make water using these minerals - Epsom salt and sodium bicarbonate, use the Barista Hustle two-bottle concentrates: https://www.baristahustle.com/blog/diy- ... pes-redux/ . Barista Hustle recipe 4 is the same as that Jayarr Coffee recipe.

Thanks for the clarification.
I'll start with the rpavlis first as it's the easiest. I don't see a reason to go to anything more complex if it works well and taste is no issue.

Question: How long should I wait for the formula to melt in the water? I understand it's not just shaking for 30s and that it may take a few hours for it to really melt. Is there a way to know when it's ready?

sbenyo wrote:Question: How long should I wait for the formula to melt in the water? I understand it's not just shaking for 30s and that it may take a few hours for it to really melt. Is there a way to know when it's ready?

I find that my potassium bicarbonate dissolves immediately in water. I put the powder in, add my water, then put in my machine. Never encountered a problem.

Yes, potassium bicarbonate as well as sodium bicarbonate dissolves very quickly. Many people will make up a concentrate in a bottle and even at 100x concentration it dissolves fully with a few inverts and shakes. Some people add 1.9 g of powder to a 5 gallon carboy of purified water, and fortunately don't need to pick up and invert and shake the bottle - a light swirling and a few minutes will dissolve it.

homeburrero wrote:a light swirling and a few minutes will dissolve it.

Same as my sipping a High West Double Rye

So, just to make sure... Let's say I switch potassium bicarbonate to sodium bicarbonate and use a 5 liter jug instead of a 1 gallon jug. In such case:

Concentration: 8.4g of sodium bicarbonate dissolved in 100g of water.
Dosage: 5g (or ml) of concentrate for 5 litres of distilled water for a full recepe or 2.5g for a 50%

It's not full moon yet. Will it work?

Rufus T.F. wrote:Concentration: 8.4g of sodium bicarbonate dissolved in 100g of water.
Dosage: 5g (or ml) of concentrate for 5 litres of distilled water for a full recepe or 2.5g for a 50%

It's not full moon yet. Will it work?

Yes. Your concentrate is 1 mol/L and diluted 5/5000 you have the 1 mmol/L bicarbonate concentration that Dr. Pavlis recommended.

P.S. [Edit addition] I should add that 8.4g in 100 ml is near the solubility limit for sodium bicarbonate at 20℃. If you store that in the fridge you'll probably get a precipitate. You could shake well before pouring off the 5 ml, but probably better to use a more dilute concentrate, perhaps 8.4g in 500ml of water, then add 25g of concentrate to 5 liters. This should avoid any precipitation, and pouring out 25 gram or ml into a scale or graduated shot glass is easier to get right than 5g (about 1 US teaspoon) would be.

homeburrero wrote: P.S. [Edit addition] I should add that 8.4g in 100 ml is near the solubility limit for sodium bicarbonate at 20℃. If you store that in the fridge you'll probably get a precipitate. You could shake well before pouring off the 5 ml, but probably better to use a more dilute concentrate, perhaps 8.4g in 500ml of water, then add 25g of concentrate to 5 liters. This should avoid any precipitation, and pouring out 25 gram or ml into a scale or graduated shot glass is easier to get right than 5g (about 1 US teaspoon) would be.

Yep, learned that in action Putting the solution on the cup tray and warming it up helped to dissolve the final bits but I should probably just double the amount of water to avoid trouble. Thanks!

If I made a mix with Sodium Bicarb vs. the Potassium bicarb I have been using, would there be any possibility of corrosion damage to my boiler? I am considering this to see if there are any taste improvements.

Assuming the rpavlis water recipe is purposed for espresso, is there an alternative recipe to maximize both brew and espresso?