I’ve been taking a closer look at Martin Lersch’s DIY Mineral Water Calculator (Spreadsheet download here) with the goal of making it practical for the average foodie. The advantages of making your own mineral water are obvious: It probably tastes better than your tap water, it’s cheaper than bottled water (for example, a 6-pack of 9 ounce Perrier bottles is 6 bucks), and you don’t accumulate all those plastic bottles to clog up landfills. The main problem you’ll run into is the very tiny amounts of salts used to clone specific brands – for example, a typical “recipe” calls for 23 milligrams (mg) of salt while the smallest measuring device in most kitchens is a quarter teaspoon that can accurately measure most solids down to about 500mg. A good kitchen scale measures grams, but round the results to integers so when the digital readout says “1” you are really somewhere between 0.50 and 1.49mg. A scale accurate to the milligram level is not that expensive, but most gainfully employed folks will use it very infrequently.
The solution is a solution. All the salts used are water soluble, of course, and liquid measurements of solutions are reliable. The process is two stage: Prepare a high concentration solution of each salt and then mix small amounts of those into a larger amount of tap water or distilled water. Chemists use the term “q.s,” which sounds cool until you learn it only means “quantity sufficient” when preparing solutions. This concept greatly simplifies matters: You simply place the measured amount of salt into a measuring container and then fill with water to the amount specified. I shouldn’t have to mention the meniscus, the crescent-shaped surface caused by liquids in containers, because you probably remember from high school chemistry that you read your measurement from the center of the meniscus, not the edges (where the measurement marks are). The amounts used in the examples are large enough, relative to the meniscus and overall accuracy, that it won’t matter that much.
While your digital scale with the English/Metric switch (look on the bottom) does a lousy job of measuring a single gram (it can be off by as much as 50%), the accuracy improves as the weights increase. I’ve settled on 10 grams as a practical amount to measure, meaning that it will be somewhere between 9.50 and 10.49 grams – off by a maximum of 5%. The 10 grams of salt will be used with water sufficient for 32 ounces, filling a one quart canning jar which can be easily capped so the liquid won’t evaporate (concentrating the solution). At that concentration, your smallest kitchen measuring device, the quarter teaspoon, can accurately measure about 3.4mg - good enough for a cook.
These are the salts used in the Lersch spreadsheet, along with their common names:
NaCl Kosher Salt
NaHCO3 Baking soda
MgSO4 Epsom salt
Mg(OH)2 Milk of Magnesia
Ca(OH)2 Slaked lime, pickling lime, CAL
Kosher salt and baking soda come from the grocery store, Epsom salt and milk of magnesia are available in any pharmacy. Gypsum can be found in stores with home-brewing supplies (or Amazon) and pickling lime with pickling supplies at a grocery store or hardware (or Amazon). Using pickling lime to crisp pickles has fallen from favor in recent years because, if not properly washed off, it can neutralize the vinegar and cause the pickles to spoil. I say that only because it makes it a little more difficult to find.
For all of the salts except milk of magnesia, just weigh 10 grams, place the salt in a quart jar, add a small amount of distilled water to dissolve, and then fill to the one quart mark. Milk of magnesia is already in a solution, but my bottle of Phillips’ tells me that each tablespoon of it has 1200mg of magnesium hydroxide. So, to get 10 grams of that, measure 4 ounces (8 tablespoons) to get 9600mg and add a teaspoon more (400mg) to get 10000mg or 10 grams. Put that in the quart jar and “q.s.” as before. Label the bottles, use the lids, and you can store them indefinitely.
For a practical exercise, let’s make a gallon of “Perrier.” I could use my tap water since I know it contains 31mg of calcium and 34mg of sodium per liter (the Lersch spreadsheet allows you to plug in mineral content for compensation and your local utility has that information), but I also found out that March is the month that they dump in a bunch of chlorine and I don’t want that so I’m using distilled water (97 cents a gallon across the street).
Take a look at the relevant part of the spreadsheet. First off, you’ll notice that the amounts of salts required are for one liter of water and we’re making a gallon. No problem, 1 US gallon = 3.78541178 liters, so we’ll just multiply the amounts times 3.785…something. In other words, instead of 23mg of NaCl we need 87. We put 10mg salt in 32 ounces of water, so each liquid ounce has 312.5mg (that number will be the same for all the salts). We do some magic conversions and see that is 1½ teaspoons of our NaCl solution (more on those magic conversions to come). Not very much, is it? Similarly, we do all the salts and come up with this:NaCl Kosher Salt solution 1½ teaspoons
NaHCO3 Baking soda solution none
MgSO4 Epsom salt solution 2¼ teaspoons
CaSO4 Gypsum solution 2½ teaspoons
Mg(OH)2 Milk of Magnesia solution none
Ca(OH)2 Slaked lime solution 6 tablespoons+½ teaspoon
Practically, for the slaked lime, since one ounce=2 tablespoons, you can measure 3 ounces in a measuring cup and then add ½ teaspoon. Place all solutions into a gallon container (such as the one the distilled water came in) and “q.s.” to the one gallon mark.
All of these amounts came from converting 312.5mg/ounce of our starter solutions into mg/gal for the Perrier and then converting that into practical kitchen measurements. This is done by a process called “math,” but that’s a bother and since the bottom part of Mr. Lersch’s spreadsheet is unprotected we can use that to do all the dirty work.
Here’s what that part of the spreadsheet look like for me, so far.
I just converted one salt at a time and manually entered the amounts required, but version 1.0 will take the amounts (mg/L) from column L and do all the conversions at once. Here is what each entry does:Water (ounces) B40 manually entered “32”
Salt (grams) C40 manually entered “10”
Mg/ounce D40 calculated =C40/B40*1000
mg/L of salt req. F40 manually entered “257”
mg/gal salt G40 calculated =F40*3.78541178
ounces liquid H40 calculated =(G40/D40)
TBL I40 calculated =H40*2
Teaspoon J40 calculated =J40*3
Quarter K40 calculated =K40*4
All fine and dandy, but floating point results like 74.71 for quarter teaspoons is not very useful, so I used the row below to convert TBL, teaspoon, and quarter to integers that added up to the correct amount. Kinda sloppy, I know, but version 1.0 will be prettier. Here are the formulas for integer conversion:
TBL I41 calculated =INT(J40)
Teaspoon J41 calculated =INT((J40-J41)*3)
Quarter K41 calculated =INT((K40-INT(K40))*4)
This should pretty much give you an idea if you want to enter your own conversions for the 8 mineral waters cloned on the Lersch spreadsheet.
Perrier is not carbonated, so let’s do one where we can give the SodaStream a workout – Gerolsteiner.
NaCl Kosher Salt solution 1 TBL + 1½ tsp
NaHCO3 Baking soda solution 4 ounces (8 TBL) + 1 tsp
MgSO4 Epsom salt solution 2 TBL + 1 tsp
CaSO4 Gypsum solution none
Mg(OH)2 Milk of Magnesia solution 5 TBL + 2 tsp
Ca(OH)2 Slaked lime solution 7 ounces + 1 TBL + 1½ tsp
Combine with distilled water as with Perrier, then carbonate. If you don’t feel like fixing up your own spreadsheet, do not despair. I’ll post other “recipes” in a future post. For now, let’s go out singing…