Safety First!

When the device is used according to instructions, and operated properly, the pressure within the system will never exceed about 50 psi which is comparable to the pressure found in a typical soda bottle sitting on a store shelf at room temperature.

pressure vs time  plot

Plot showing pressure (psig) vs time (s) as carbonating bottle is charged with CO2 and shaken

Since the two ingredients; baking soda + vinegar or citric acid, are pre-measured, there is a limited amount of CO2 generated. As the graph above reveals, the pressure rapidly falls within several seconds when the MIXER (carbonating bottle) is shaken (magenta colored bars). In fact if the MIXER is continuously shaken, the pressure will never exceed the final pressure - here about 27 psi. This carbonation cycle was complete in 1m:50s.

To operate the device properly, the following rules must be applied:

  1. Shake the MIXER bottle at least once per second
  2. Use a starting beverage that is cold. A temperature of 45 Deg F (7 Deg C) or less is good, 37 Deg F is better
  3. Use the correct measured amounts of carbonation powders for the desired quantity of carbonation and beverage bottle size

Adhering to these three rules should provide safe operation. The use of a 55 psi rated vinyl tube in the design also acts as a safety feature in the event that proper operation is not followed, although it should not be relied upon to guarantee safety.

Do keep in mind that you are building a device from scratch, and that the sourced components, and construction quality will vary from one unit to the next. It is the responsibility of the builder and operator (often the same)to ensure that the device is of sound construction, and that it is operated in a safe manner. Regardless, you should never allow a child or someone who is unfamiliar with the safe operation to use this device.

Safety Glasses ?

Although I have never worn these while operating the device, the most safety conscious operator may choose do so simply because it is good practice.

PET Bottle Pressure Ratings and Life

PET soda bottles are typically rated to withstand at least 150 psi. This means that they can withstand a hydro pressure test in a factory. The test is performed by filling the bottle with pressurized water rather than a gas. In the real world, a PET bottle should be able to withstand the pressure of a soda bottle left in a hot car, which can exceed 100 psi. The 150 psi rating provides a margin of safety. Under normal pressure usage, the bottle plastic can typically withstand up to 45 deg C (113 F) temperatures, before deformation starts to occur. At room temperature, these bottles start to show physical deformation at around 80 psi.

In the early days of PET Soda bottle use, a number of recorded incidence of cap missiling occurred when the consumer unscrewed the cap (think champagne cork) leading to injury. In the 1980s the thread was redesigned to include four slots on the bottle side of the threads. These slots act to allow the pressurized gas to escape before the threads are completely disengaged.

Bottle Life

While there is no simple way to estimate the life of a PET bottle, proper care will allow them to be reused many times (100s). Eventually however, plastic fatigue may occur due to the many charging and discharging cycles. I replace my bottles annually as part of my maintenance routine.

Hot water, alkaline detergents, dropping or deep scratching should be avoided. Damage to threads either on the cap or bottle should also be avoided. When in doubt, replace with a new bottle.

Questions? You can email me at:

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