Easiest way to make rpavlis water? - Page 5

#41: Post by **Sideshow** » December 7th, 2020, 4:34 pm

ethiopianbuffman wrote:Ok now I know why people don't add .19g to 1 gal because it is tedious to get that amount.

Nah, milligram scales are cheap and easy to get. I add .100 grams (100 mg) to 1000 ml (1L) of water. It's easy and convenient. I could measure out .19 grams (190 mg) just as easily.

February 12th, 2021, 10:26 am

homeburrero wrote: A correct version of your approach would be 1.0 gram of potassium bicarbonate dissolved in 100 ml (100 grams) of distilled water. That produces a 10 g/L, (or 10 mg/ml) potassium bicarbonate concentrate. Then if you add 10 ml (10 grams) of this concentrate to distilled to a make a liter, you get your desired 100 mg/L of potassium bicarbonate in your water.

Hi Pat, and if adding this concentrate to a gallon of distilled water, I will multiple by 3.78, correct (meaning, I will add 37.8 ml (37.8 grams) of concentrate to a gallon of distilled water). Related question: how vigorously do you shake your concentrate and brew water to make sure it's dissolved?

Sorry for the stupid questions: my 1-year old BDB is currently in the shop because it started leaking and I am now wondering whether I made an error when I made my water, and I am trying to prevent future problems. Thanks.

#43: Post by **Willinak** » February 12th, 2021, 3:48 pm

homeburrero wrote:^^^^^ that one also looks good.

Another popular approach for folks that start with 5 gallon jugs of distilled is to simply add 1.9 grams of potassium bicarbonate to the full container. (That gives you the full strength, 100 mg/L water.)

Pat, I'm using 5 gal distilled carboys, so the above is what I would add for the carbonate, you made it easy peasy. What would I add for the magnesium? BTW, I'm normally a Medium roast guy.

February 12th, 2021, 4:03 pm

homeburrero wrote:That's within expectations. The expected conductivity of a 100 mg/L KHCO3 solution at 25℃ should be 116 µS/cm, On an NaCl calibrated 'TDS meter' would read about 60 ppm, and that's what many people are reporting with their inexpensive TDS meters. If the water temperature is not 25C or if the meter is out of calibration it can be quite a bit off from that.

Pat can you please remind us all to where we can find the conversion formula? Thanks.

February 12th, 2021, 7:14 pm

espressoccer wrote:Hi Pat, and if adding this concentrate to a gallon of distilled water, I will multiple by 3.78, correct (meaning, I will add 37.8 ml (37.8 grams) of concentrate to a gallon of distilled water). Related question: how vigorously do you shake your concentrate and brew water to make sure it's dissolved?

That's correct. And potassium bicarb is very soluble and a fine powder like the LD Carlson should dissolve fully if you invert and shake the bottle for 10-30 seconds or so. You can keep the concentrate in the fridge and it will stay clear and fully dissolved, then little or no shaking is needed after you add that to your brew water mix.

Willinak wrote:Pat, I'm using 5 gal distilled carboys, so the above [1.9 grams of potassium bicarbonate to the full container] is what I would add for the carbonate, you made it easy peasy. What would I add for the magnesium? BTW, I'm normally a Medium roast guy.

For the rpavlis recipe you don't need to add any magnesium salts. If you want to try some anyway to get some hardness minerals, and if using Espom salts you might try about 2.3 gram per 5 gallon. That would give you a total hardness of 51 mg/L (CaCO3 equivalent). Then maybe try about twice that if you want to give a high hardness water a taste. If the harder water doesn't taste better then I'd say just skip the Epsom salt.

CarefreeBuzzBuzz wrote:Pat can you please remind us all to where we can find the conversion formula? Thanks.

For potassium bicarbonate the conversion factor is fairly linear across 20 - 200 mg/L at about 0.86 -- you multiply your µS/cm value by 0.86 to get your mg/L value. So for the typical inexpensive NaCl calibrated meters that use a conversion factor of 0.5, the meter's ppm reading is lower than the actual potassium bicarbonate TDS by a factor of about 0.6.

Whenever I need an estimate of the conductivity of a given concentration of salts I generally use a this handy online tool: http://www.aqion.onl/show_ph

#46: Post by **boren** » July 17th, 2021, 7:24 am

That's how I do it:

To make the RPavlis concentrate: Mix 5 gram potassium bicarbonate into a 500 ml bottle (good for making 12.5 gallons)
To make the machine-ready RPavlis water: Mix 40 ml of concentrate into a gallon (or 4 liter) of water

#47: Post by **Carl K** » July 26th, 2021, 10:53 am

I do the same as Boren, except I make 1 liter of concentrate because a 1 liter bottle is easier for me to get:

I also wrote the recipe on the jugs so it's one less thing to remember.

This is my 1 liter concentrate bottle:

This is my gallon of espresso water:
Also 38 ml is essentially the same as 40 ml
And a hint, 1 ml weighs 1 gram. So you can use the same scale you used to weigh out the potassium bicarbonate to weigh out 38 or 40 grams of concentrate to put in your gallon jug.

#48: Post by F1 » August 2nd, 2021, 1:26 am

In the first page of these thread one user recommends a concentrate of 10g potassium bicarbonate diluted into 100g of water and then add 3.8g of that concentrate to a gallon of distilled water. Is the end result the same as above?

#49: Post by **jgood** » August 2nd, 2021, 1:48 am

I believe the final concentration would be the same - the advantage of the last recipe (10 gram per liter for the concentrate) is that you are measuring 38 gr of the (more dilute) concentrate which I think would be easier to measure accurately. Rereading the thread I did notice that it was mentioned that one could (should) use a more dilute version for dark roasts - in this case 19 grams of the concentrate. Is this correct?

#50: Post by **homeburrero** » August 2nd, 2021, 2:04 am

F1 wrote:one user recommends a concentrate of 10g potassium bicarbonate diluted into 100g of water and then add 3.8g of that concentrate to a gallon of distilled water. Is the end result the same as above?

Yes, compared to Carl K's, your concentrate is 10x as strong so adding 1/10th as much comes out the same.

Making this strong a concentrate puts you at risk of not getting a fully dissolved clear concentrate. In this case, using potassium bicarbonate, you should be OK even at refrigerator temps. If you were to substitute an equivalent amount of sodium bicarbonate (baking soda) which is less soluble you probably can expect that it would not fully dissolve.

An advantage to using the weaker concentrate (10 g in 1000 ml) is that it's so easy to measure an amount reasonably close to 38 ml. A shotglass will do. Measuring reasonably close to 3.8 ml (3.8 gram) is a little harder -- but I think you'd be close enough with 3/4 teaspoon if you didn't want to get out the scale for that.

[Edit addition] At 10g potassium bicarbonate in 100 g you have a 10% solution, and according to Dr Pavlis might give you a potassium sequicarbonate precipitate. Harmless and OK but you'd want to give it a good shake before adding.

In Help to identify La Pavoni Europiccola pre-millenium :

rpavlis wrote:You may find a slight precipitate forms when a 10% solution of potassium bicarbonate stands for a while. This precipitate is harmless. It is actually a bit of potassium sesquicarbonate. Its formula is K₂CO₃*2KHCO₃*3/2H₂O. It forms because it has a more stable crystal latice than either potassium bicarbonate or potassium carbonate. It does not form in less concentrated solutions of potassium bicarbonate.