Seltzer Intermission

As I wait for the wedding pictures to come in from our esteemed photographers, I thought I’d take this time to share with you my recent adventure at -109°F.

For my birthday this past year my folks gave me a Soda Stream! As a passionate seltzer drinker, the soda stream is a soda dream. Custom carbonated water on demand is surprisingly convenient. Jen and I drink seltzer every night with dinner, so it really makes cents… or does it?

The machine operates using CO2 cartridges. Each cartridge claims to produce 60Liters of carbonated beverage. For Jen and me, this quantity is likely inflated because we are generous, some might even say profligate, with our bubbles. But for the sake of math, let’s presume the 60L thing works out.

At the local grocery store, we can get two liters of setlzer for $0.89. That’s a mere 44.5cents a liter. Frankly, the fizz fades furiously once one opens the orifice – but still, that’s cheap! Soda stream refills run about $15/canister. That’s $0.25 per liter. A savings of 19.5 cents per liter!

With a $100 price tag on the machine and the price of the refills, it would require ~360 liters to break even after initial investment. Better than the store brand? yes. Much better? no.

Now if only there was a way to refill one of these canisters myself.


I did some research online. While many lauded the use of paintball gun refilling methods, I was hesitant because of the whole ‘food grade’ thing. While CO2 is CO2, I was worried about the oils used in lubrication of the paintball CO2 valves. There was, however, a video online that suggested the use of Dry ice to refill the canisters. Dry ice is the solid form of CO2. It is safe for food and except for the fact that it’s so cold it burns to the point of disfigurement. (Fun Fact: Dry ice is about -109°F)

No problem!

The plan would be to partially fill the empty canisters with dry ice. As the temperature of the canister stabilized, the dry ice would melt under pressure into liquid CO2. When that liquid was released into water it would rapidly depressurize into gas. Ta-da! Seltzer!

I decided to give it a shot.

Tools: meat tenderizer, wrench, gloves, dry ice, vise grips
Tools: meat tenderizer, wrench, gloves, dry ice, vise grips

I have two canisters, making refills extra convenient. I picked up 5lbs of dry ice at a local ice store for $11.99 and the adventure began!

This is what 5lbs of dry ice looks like.
This is what 5lbs of dry ice looks like.

First, I used a release valve on the side of the canister to make sure that both canisters were completely empty. Next, I used a vise and a wrench to unscrew the valve atop the bottle.



Next, I put on my safety glasses and thermal gloves, covered the ice with a dish towel and smashed it to pieces.



Admittedly, I thought that the dry ice would be cold enough not to stick together. I imagined it pouring from a cup like dry sand. Such was not the case. It clumped up like snow.

This was completely useless for pouring.
This was completely useless for pouring.

This made my make-shift paper funnel completely improbable. Even with a plastic funnel I had to jam the dry ice into the hole using a skewer.

Note: Failed paper funnel on the counter.
Note: Failed paper funnel on the counter.

I filled each container up to about 50% full. Then capped ’em.

For the most part, this was not a frightening endeavor. HOWEVER, it sketched me out a bit that after I finished filling them, both containers frosted over somethin’ fierce. This isn’t surprising because dry ice is COLD. Yet it freaked me out enough to isolate the canisters in the garage and wait inside while the canisters warmed up.

Once the canisters were room temp, I transported them gingerly to the condo where we installed the first of the two canisters into the soda stream. I depressed the switch… and FIZZ! Beautiful fizz at half the price!

Things I would do differently:

1. At the ice store where I purchased the dry ice, 5lbs was the minimum. I really only needed 4lbs for two canisters. For my next refill adventure, I will most certainly be seeking other dry ice vendors.
2. $12 for this is CRAZY EXPENSIVE. As a comparator, my quick online searches suggest that I should be able to get dry ice for about $1/lb. See #1.
3. I need to improve my crushing method. Dry ice went everywhere. It was hard to contain underneath the towel. Apparently you can order dry ice in 0.25″ pellets – this would be awesome. See #1.
4. I should have weighed the canister before I started so I’d know precisely how much dry ice to add. I wrote above that I filled each to about 50%. It was probably closer to 75%, but I had no precise gauge. As we all know Pv=nRT. If you add too many Moles (n) your pressure could be higher than the defined limit of the container – this could lead to trouble (i.e. exploded canisters). This is why I let my canisters warm up in the garage far away from my body. If I had weighed the containers when they were new I would have been able to closely approximate the moles of CO2 (~44grams per mole for dry ice). I was reassured however by the release valve on the canister. I figure if I added too much, that release valve would have failed and the results would not have been catastrophic.
5. I had/have mild concerns about the O-ring in the container. With the excessive cold of the dry ice I worried about the failure of the o-ring a la the Challenger. When we finish consuming the fizz, I will carefully inspect the o-ring and report back.

4 thoughts on “Seltzer Intermission

  • 11/12/2013 at 1:28 pm

    We used dry ice in the lab all the time when doing solvent evaporations. Put some IPA and dry ice in a Dewer, then put a solvent trap in the cold fluid between your sample and the vacuum pump, to protect your pump from solvent fumes. Dry ice isn’t terribly dangerous, just don’t like eat it or touch it bare handed (very much, a few seconds is okay if not recommended) and you’ll be fine.

    A fun thing to do? Put a chunk of dry ice on the counter and rest the back of a spoon on it. The spoon will hum (escaping gas vibrates the spoon).

    HOWEVER I would be very very worried about overpressurizing the canisters, or canister failure from repeated stress or whatever. Letting them pressurize away from your soft body parts was a good idea. But you have essentially made a pipe bomb, and BLEVEs are serious explosions (youtube a few of those up before you do this again, they can be quite impressive). I, personally, probably wouldn’t do this.

    • 11/12/2013 at 1:45 pm

      I agree, the appeal of saving money by pressurizing my own canisters with gas, very, VERY, low to me. I’m still terrified of the big gas canisters that we used to have in the lab at work after I saw the Mythbusters where they sent one of them through a cement block wall.

  • 11/12/2013 at 3:34 pm

    Might I remind you, dear Michael, that the initial financial outlay was ours, not yours (Happy Birthday), so you save money from the get- go by purchasing the correct cartridges.

    Time is money. Save Jen. Save yourself. Buy the refills.

    • 11/13/2013 at 10:15 am

      I was really hoping you would pop in on this post!


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