Monday, June 25, 2018

Carbonating Water: Making Seltzer at Home

Pouring a glass of carbonated water from the tap!The only dedicated tap on our kegerator is the one for carbonated water. All beverages are marked up when you buy them by the serving rather than in bulk, but carbon dioxide dissolved in water is one of the most egregious. Making 5 gallons at home costs less than a dollar. When it comes to bottles, smaller is better because after opening the bubbles begin to escape. Having it on tap ensures the water is always ideally carbonated, and wonderfully cold (especially compared to our 75F/24C summertime tap water).

Seltzer, sparkling water, fizzy water, and bubbly water are synonyms, referring to water with carbon dioxide bubbles. In the US, "mineral" water is required to have 250 parts per million total dissolved solids (TDS), usually from a natural spring. Club soda or soda water is similar, but usually has the minerals added to it. Adding quinine (from cinchona tree bark) would turn it into tonic water. I don't think there is any need to get technical when making your own.

Luckily the process to carbonated water at home couldn't be simpler, if you already have a kegerator. Fill a keg with good tasting water (e.g., carbon-filtered tap water, reverse osmosis) and connect to a CO2 tank. Set your regulator for between 20-30 PSI, depending on how strong you want the bubbles to be. Once the keg is connected vent the head-space and then let the water chill and the CO2 infuse. To speed things up, once the water is chilled, you can shake the keg to speed up the absorption of the gas. Cold water can hold onto CO2 much easier, so you're wasting your time to shake room temperature water.

We add a small dose of chalk (calcium carbonate) to move our tap water closer to the profile of Perrier. Chalk doesn't readily dissolve at water's roughly neutral pH, but it is happy to once there is carbonic acid in solution. This is essentially the same thing that happens with acid rain meets limestone, the carbonic acid dissolved in the rain eats away at the calcium carbonate in the rock.

My Treated Water

Calcium
Chloride
Sulfate
Sodium
Magnesium
Carbonate
150
30
50
15
10
250

Perrier
Calcium
Chloride
Sulfate
Sodium
Magnesium
Carbonate
160
19
30
9.6
4.3
366

The calculator on this site includes many more profiles if you have a favorite mineral water.

If you are a fan of flavored seltzers like Polar or La Croix, you could add a small dose of a natural flavoring of your choice. It is best to dose a glass to taste and then scale up, a little goes a long way when it comes to these super-concentrated "natural" flavorings like those from Amoretti. You can also use actual natural ingredients like citrus peel. In that case I'd remove those after hanging them in the keg for a day or two. If you stick with plain water there is no need to clean or sanitize between fills, but with strong flavors you may need to clean if you are switching flavors.

This post is also available in video form on my YouTube channel.

16 comments:

Unknown said...

I too like to keep soda water on tap. I like mine with a twist of lemon or lime.

When my kids want a sweet treat, I let them make flavored soda. 2 cups of water, 2 cups of sugar, and 2 tbsp of any flavoring extract. Their two favorites are coconut soda and almond soda. Add an oz of the syrup to the soda water and it's good to go.

They have been known to lug a couple of jars of soda flavor and my small kegerator down the local farmer's market in lieu of a lemonade stand.

The Mad Fermentationist (Mike) said...

Very nice! Our two-year-old niece has become a fan of plain carbonated water, although the excitement of pouring it is the main attraction it seems.

Florin said...

Presumably, oxidation isn't an issue here. So, are you purging the headspace just to make sure it's only CO2 being dissolved into the water?

The Mad Fermentationist (Mike) said...

Exactly. Pure CO2 will dissolve into the water more quickly than a mix of gases thanks to partial pressure laws. If ~40 % of the gas in the headspace is nitrogen from the air, the effective CO2 pressure will only be 60% of what it would be with pure CO2.

ethan said...

Do you keep the keg at 20-30 PSI or drop it lower for serving?

The Mad Fermentationist (Mike) said...

I maintain the pressure at ~25 PSI. You could certainly go up to 30 PSI to speed up carbonation, and then lower it a little for serving, but too far and the water will slowly get less carbonated.

Dave said...

I had that Amoretti sample kit sitting around so I thought I'd give a try making flavored seltzer. I think we spend $10 a week on flavored Polar at our house, so it'd sure be nice to make my own. I went all the way up to 100x the suggested dosing rate for beverages, but still didn't get much flavor. This was the Mango water-soluble extract (suggested .01-.02%, I gave up after .25oz in 16oz). Any tips?

James said...

If I ever get a keg setup I think I will get a small keg and experiment with carbonating my favorite wines. It occurs to me that some cocktails might also benefit from some extra carbonation.

The Mad Fermentationist (Mike) said...

Dave, maybe you just aren't sensitive to the aroma compound? I put a drop of the Mango extract into an 8 oz glass of carbonated water and it was more than enough for me. Sort of reminded me of kid's tropical toothpaste.

I've been to a few bars that have pre-blended cocktails on tap (makes it easy for the bartender). Works well if you are drinking through the keg quickly, but at home you'd want to make sure it'd hold up for as long as you expect the keg to last.

Josh Butler said...

My tap water run usually has a pH of around 8-9. If I add the 10 grams of chalk required to meet the Perrier ion content wouldn't the final product be over the top basic? Maybe I'm missing something.

The Mad Fermentationist (Mike) said...

The carbonic acid will provide the balance. You can certainly start with just carbonated tap water as a baseline and then add the chalk to the second batch to compare.

Josh Butler said...

Very interesting. The still water went into my keg at a pH of 6.5 and, once carbonated, read at 4.0.
What prevents beer from having such dramatic acidification during the carbonation process?

The Mad Fermentationist (Mike) said...

It does, we just read and discuss the final pH of degassed samples of beer.

smallbbrewer said...

I find that I go through so much more fizzy water than beer!
I now have a selection of fruit juices, syrups and chopped up fruit to throw in.

Thanks for the mineral profiles on creating specific 'styles' of water, thats a step I haven't taken yet!

Unknown said...

was that about 5 grams worth of chalk you added to the water? how much would you add to RO

The Mad Fermentationist (Mike) said...

About 1.5-3 g of chalk per gallon of RO will get you in the same ballpark for calcium and carbonate.