It's fairly simple to begin carbonating things; here's a list of the things you'll need to follow this instructable step by step:
-CO2 supply: This can vary greatly between setups. I use a 20# tank, but you can use nearly any size CO2 tank with a regulator. Heck, I've even used 9-20oz paintball tanks to carbonate things! You can find good used 20# tanks on eBay (I got mine for around $40)
-A Regulator -this is a good one.
-To carbonate liquids, you'll need an empty 3L soda bottle.
-A clamp-in schrader valve for the 3L soda bottle - you can find these at nearly any auto parts store. Here's one that will work. Here's another.
-To carbonate fruits and other objects that you can't pour, you'll need to build a pressure vessel out of PVC pipe and other standard fittings that can be found any hardware store. This will be discussed in detail later in the instructable.
Step 1: Setting up your carbonating equipment
Twenty pounds of CO2 can carbonate a lot of water. Remember that no matter what you're carbonating, it is still CO2 dissolving into water (this is why high-water-content foods work best). A 20# tank holds enough CO2 to highly carbonate around 500 gallons of water - with this amount you could drink 2-3 liters of home-brewed seltzer per day and not have to refill the tank for several years! The CO2 cost of what I make in this instructable is only a few cents!
In addition to the tank, you'll need a suitable regulator to bring the gas down to working pressures of under 100psi. I use a regulator that allows me to adjust between 0-100 psi, pressure which are more than suitable for carbonating things. You can find a good regulator at any home brewing store. Ideally it should have two pressure gauges (one for the high-pressure side and one for the low-pressure regulated side), a safety relief valve, and some sort of shutoff valve.
Note: Please DO NOT try to use a tank without a regulator - CO2 is stored in a cryogenic liquid state in the tank at pressures of around 1000psi and opening the tank valve without a regulator attached could lead to a very dangerous situation! I suggest that you read and become familiar with the MSDS sheets for CO2 - it's a very safe gas to work with as long as some basic procedures are followed.
Step 2: Build the pressure chamber
Building the pressure vessel for making soda is simple: the only items you'll need are an empty 3 liter soda bottle and a clamp-in schrader tire valve. Just drill a suitable size hole in the bottle cap and attach the schrader valve, using it's threaded nut to clamp onto the cap with the included rubber grommets. Using a plastic soda bottle is actually quite safe as long as the pressures are kept to a reasonable level. The pressure inside an un-opened bottle of soda that has been shaken up and left in the sun can easily exceed 100psi - these bottles are over-engineered to ensure safety and built to last. You could use a 2 liter bottle instead, but I prefer 3 liter bottles since the plastic is much thicker and the neck is wider, allowing easier pouring. The neck on a 3 liter bottle is also wide enough to fit ice cubes inside, which helps keep the liquid nice and chilled, which in turn will help to hold carbonation longer and speed the dissolution of the CO2.
If you intend on carbonating things like fruit which you can't pour, you'll need to make a pressure vessel out of some PVC pipe. When done properly, this can be an extremely easy and safe way to carbonate anything that will fit inside. I made my chamber out of 2" PVC pipe, which has a working pressure of over 200 psi. A very important thing to remember is that these ratings are usually at around 70 degrees Fahrenheit, and if you chill the PVC it will become more brittle and therefore weaker. Refrigeration temperatures (no lower than 40 degrees Fahrenheit or so) are fine, but PLEASE do not stick ANY pressure vessel made from PVC in the freezer while it is pressurized!! It's pretty hard to enjoy your nice carbonated fruit when there is shrapnel embedded in your face.
I just placed an end cap on one side of the pipe, and a threaded adapter on the other side with a threaded plug. There are some standard brass plumbing fittings which are threaded into the PVC cap and are meant to supply CO2 to the chamber and monitor the pressure. The pictures should be pretty self-explanatory, but feel free to leave a comment if you're unsure of anything.
A suggestion: the chamber I made is much too long to fit into nearly any household refrigerator I've found. If I had the chance to build the pressure chamber again, I would definitely build it so that it was shorter and wider, maybe using 4" PVC instead of 2" and halving the height. Just remember that the greater the diameter of the pipe, the less pressure it is rated for. Moving up to schedule 80 pipe would help with this.
Step 3: Prepare your fruits and juice
I find that smaller pieces tend to absorb the CO2 easier, so I always slice fruits into small pieces. I've sliced the apples into 16ths here, but 8ths works fine as well.
One neat thing about the carbonation process is that the CO2 will halt the browning of the apples - apples and pears brown upon exposure to Oxygen but in the presence of a 100% CO2 atmosphere this process is halted!
Step 4: Carbonate!
1. Pre-chill the fruit in the refrigerator. The colder the better, since the CO2 will dissolve much easier in cold liquids than warm liquids.
2. Open the PVC pressure vessel by unscrewing the lid and place the cold fruit inside.
3. Seal the pressure chamber by screwing the lid back on tightly. I like to use a little Teflon tape on the rough PVC threads to ensure that there are no leaks.
4. Connect the pressure chamber to the CO2 tank using the quick disconnects.
5. Adjust the regulator output to between 40-60 psi. I like to pressurize my fruit right at 60 psi.
6. Start pressurizing the chamber by opening the ball valve. Let it fill until the gauge on the chamber reads 60psi and then close it.
7. At this point it might be a good idea to check for any leaks by using soapy water. The next step requires letting the chamber sit for a while and even a small leak could leave the chamber empty in an hour.
8. Now, you wait. Depending on the fruit, temperature, and pressure, carbonation should occur between 20-60 minutes. In my experience it doesn't really hurt to go much longer, even allowing the fruit to sit under pressure for 24 hours resulted in only a few grapes splitting open. Feel free to experiment with the fruit, pressure, and duration to suit your tastes.
9. Slowly open the ball valve to slowly let out the pressure. It's important to do this gradually over the course of 30 seconds or so, because suddenly releasing all the pressure at once could result in some exploding fruit, making a big mess. Once the pressure gauge shows zero, you can unscrew the lid and enjoy your newly carbonated fruit!
1. Pre-chill the juice in the refrigerator. Again, the colder the better.
2. Connect the tire chuck to the CO2 tank using the quick disconnects.
3. Adjust the regulator output to between 30-60 psi. I like to pressurize my juice right around 50 psi.
4. Start pressurizing the bottle by placing the tire chuck over the valve stem and pushing down. Let it fill until the gauge on the regulator reads 60psi and then let go. It's important to push straight down and lift straight up, otherwise gas may leak out of the valve while filling.
5. Pick up the bottle and try to squeeze it - it should be nearly impossible because of the pressure inside. Now shake the bottle vigorously for 10-15 seconds. When you try to squeeze it again, there should be a noticeable difference in the pressure - this is because of the CO2 dissolving into the juice.
6. Repeat steps 4-5 several times. I usually do this 4-5 times, until I notice that there is no longer that much of a difference in pressure after shaking.
7. Place the bottle in the refrigerator. There will be TONS of bubbles and foam in the bottle, and you'll need to let it sit for several hours for this to go down. I usually leave the bottle in the fridge at least overnight if not longer. If you try to open it right after you carbonate, you'll have some pretty fizzy soda, but you'll also have sticky foam everywhere! It's not that fun, trust me :)
9. I've found that even after letting the soda sit for a while, it's important to very slowly release the pressure from the bottle to avoid mountains of foam shooting out of the bottle. You can either do this by depressing the stem of the schrader valve with something like a pencil or screwdriver, or very carefully unscrew the cap a quarter turn or so until you hear a nice slow hissing sound.
10. ENJOY! For some reason, this method tends to give very very fine bubbles, which results in a unique texture in your mouth.
Step 5: Enjoy!
The first thing you'll notice when you take out your fruit is the sound - you'll hear something that sounds like thousands of little bubbles crackling and popping - and that's exactly what is happening! The fruit pieces will literally be bubbling - but be sure to eat them quickly because all that bubbling means that the carbonation will only last for a few minutes!
Did you follow this instructable and make some carbonated fruit or soda? Did you take it a step further and carbonate some other food using this technique? Let me know in the comments!