I usually check the weight of an unused CO2 bottle and compare the weight to the one I am about to replace which gives an indication of how much CO2 is left in the bottle I am about to stop using. I remove the protective seal and cap, weight the full bottle, then weigh the used bottle. If the difference is less than 400g, then I assume there is still some gas in the used bottle and keep using it.
My understanding is that the cylinders may fall within some legislative rules for the storage and handling of gas cylinders. I tried searching for “storage and handling of beverage gas cylinders” and most of the references refer to commercial activities like post-mix equipment in pubs.
We never “own” the cylinders when purchased new or as refills as it is a licensed product and I assume the supplier takes responsibility for safety testing of returned, empty cylinders.
The cylinders are not tested. They are washed and inspected visually.
As to how the Australian Standards might apply?
I’m not familiar with how the standards have been interpreted in SodaStream’s instance. There are AS variations of requirements or exemptions for smaller cylinders, depending on gas, pressure and volume. IE cylinders with a high factor of safety by design, while the gas and low volume present a very low risk.
Someone might like to share any details from the neck of the bottle (AS markings) or base area indicating that a bottle has a test date, serial no etc. They may not, with the bottles intended to remain in use for as long as the owner decides? IE they retain absolute control of their bottles - legally. The gas is very cheap. The product is the container.
The gas use may be considered a food product, or skirt the legislation. One might expect there should be at least a batch or serial number for tracking on each bottle, to enable recalls where there are risks of contamination. Perhaps SodaStream have made the case it’s not necessary?
The EU SDS indicates that aside from a bursting disc and some labelling requirements:
The Aussie version is less expansive:
Note:
SodaStream manufacture all their cylinders (Aluminium body with brass fittings). This suggests they set their own standard, providing they can demonstrate it exceeds any relevant standard applicable where the product is being sold. I’m guessing this is how it works out. The linked ‘all you need to know about SodaStream CO2 cylinders’ is short on real content and long on why it’s such a great product.
The “60L” one in my hand says SEP 30 AU, ink stamp on bottom. Stamped into the Al near the top is the date 2020/07
Also stamped into the Al near the top are a number of serial numbers/standards/places of manufacture codes???
Mass of CO2 appears to be “0.478KG 1013 CO2”.
I assume the 1013 refers to standard air pressure, although they do not give the volume, which seems odd
Weight, “TARE =0.75kg”.
“ISO 7866” is presumably the relevant international standard for the vessel.
“3.2MM 0.61KG 0.630L” perhaps wall thickness of wall, mass of container (just Al,not including brass?), and volume of container?
“AA6061” I’m sure refers to Al alloy 6061, also used in some bicycle frames and components for its strength etc properties.
“PH250BAR” is perhaps the max internal CO2 pressure at standard room temp, or perhaps tested pressure of the vessel?
Further to my 24/1 post, I have lately been filling the water bottle to about 1cm from the top of the bottle, and using shorter button presses to avoid CO2 burping with shakes in between, and a longer shake at the end.
This has greatly reduced the CO2 loss upon removing the bottle from the gassing device, so I should be able to get a few more litres of carbonated water from each CO2 cylinder now.
The Material Safety Data Sheet pretty much sums it up and certainly the Sodastream refill process described on their web site seems to cover all the bases.
We are getting a little Nerdy here. I think it’s good to have an understanding of the requirements we can establish for this suppliers product. It’s a guide to what to look for with other similar products.
IE testing and acceptance is based on an initial type test, followed up with testing of a sample/s from each batch of 200. As a consequence the cylinders consumers use require a lesser standard of testing, pressure proof test or working pressure expansion test.
The other markings suggest SodaStream have processes in place to assist them to manage their product by individual cylinders, including refilling. While the interpretation appears obvious it would be better for SodaStream to say what they are and how they are used.
I’d be very interested in any info you have about how much CO2 was in the cylinders i.e. the difference between the cylinder weight when bought full and when completely empty? It might vary a bit but should not be less than about 400g.
So far I only have that info for one cylinder and it seemed to have contained less than 400g of CO2…
Interesting. I too fill the bottle with cold water to about 1 cm from the top and inject the gas in 3 short bursts with an interval between each. However, I still get a burp, indicating gas loss, when I remove the bottle. But I do not do the shaking. I presume that you shake the bottle while it is still attached to the machine?
If you keep a record of how many bottles or litres of carbonated water you now get compared to previously, I’d be very interested in the figures.
I’ll be resuming soon my record keeping which was suspended because the partly used cylinder i was given, and have been using for the past few months, is just about empty. I’ll share later the results from the suspended trial but that may be several months away 'cos, assuming that there was at least 400g in the cylinder, I have only used a small amount so far.
Back in the days of soda siphons with little gas bombs this was standard practice. If you want to dissolve CO2 efficiently:
Chill the water before you start. This increases the solubility of CO2.
Shake as you go. This brings the gas in contact with the water and increases the rate of reaching equilibrium. As the gas is under pressure it makes it dissolve.
People are used to shaking an open fizzy drink making it bubble and lose gas. In both cases the shaking speeds up the process, in one case the gas goes in, in the other it comes out.
Thanks.
I have added shaking to my original tips, so the current tips are::
• Only gas very cold water, because the gas dissolves best in very cold water. (So, always have a bottle of cold water in the fridge ready to pour into the Sodastream bottle for gassing.).
• Wait a few seconds between each gas injection to allow more time for the gas to dissolve. Also,
• To further increase the amount of gas dissolved in the water, after each gas injection shake the bottle (while its is still attached to the machine).
• Wait about a minute after final gas injection before removing the bottle from the machine and putting the top on the bottle in order to allow more time for the gas to dissolve.
• Only gas water, because the gas dissolves better in water than in juice, etc.
The above assume that refilled exchange gas cylinders are being used.
The main issue with trying to dissolve CO2 in juice, cordial etc is the presence of millions of small particles which form nuclei for the gas bubbles to grow on, resulting in a significant eruption of gassy liquid when the bottle is removed!
That is one issue. Another is that mostly such fruit-based flavours are acidic which makes CO2 less soluble. Which factor is more important I cannot say as doing the sums for nucleation is beyond me today.
This is because CO₂ is only absorbed by the water the gas come in contact with. If one doesn’t mix the water by inverting, the water can become stratified…where the top contains dissolved CO₂ and the bottom flat.
Over time this will balance out as the CO₂ is percolates through the water bottle (from atoms bouncing off each other causing mixing), but overall the water will be less fizzy as the gas in effect has been diluted.
This is because the higher the temperature, the less gas water can hold. For CO₂, this is the relationship:
This graph shows that water at fridge temperature (4°C) can hold about twice as much gas as water from a tap 20-25°C). More gas = more fizz/bubbles.
However, there is also a pressure effect. Under pressure, water can hold more CO₂ under pressure. When the pressure is released, warmer water will release far more CO₂ than water at a colder temperature.
If one adds CO₂ into fridge temperature water, it is important to serve it as close to fridge temperature. If a fridge gassed water is opened at room temperature, more CO₂ will be lost meaning that the CO₂ is wasted to the atmosphere and the water being slightly less gassy than would otherwise be the case.
