Re: How does Zero Gravity softdrink(soda)work

I have not come across this product, so I am a little in the dark about its 
exact behaviour. Either I have not been checking the soft drink cabinet in 
the local milk bar thoroughly enough, or the product has not yet penetrated 
South of the border! So I will have to answer the question by imagining
what would need to be done to achieve a product of this sort that "works".

After that bit of Australian, I will have to try strenuously to speak North
American. So we have soda and drugstores, etc. But most importantly I am 
told that "little jelly beads" does not scan. So I will try "little lumps 
of jello". I am referring to items about 2 to 5 mm in diameter which are 
gelatinous, soft, wobbly, non-sticky, and edible (as I believe you are 
too!).

There is a very interesting phenomenon called "neutral buoyancy". If you 
put a stone in water, it sinks to the bottom; if you use a lump of wood 
instead it floats. The density of rock is greater than that of water, while 
that of wood is less. If you make a material with a density that is almost 
exactly the same as that of water, it will neither float nor sink, but 
wander around fairly freely, following the convection currents in the 
water. Sometimes it might adhere to a wall of the container or something 
like that and spoil the effect.

You can see much the same thing after a party with helium balloons. Several 
of the balloons will have escaped and lodged themselves on the ceiling. But 
helium slowly leaks through the skin of the balloons, and after a while (a 
few hours) the lifting power of the helium in the balloon is just exactly 
enough to carry the balloon and its string. Ten very interesting minutes 
follow during which the balloon wanders quite freely around the room on the 
air currents, before it loses enough extra helium to start dragging its 
string on the floor (you can revisit the phenomenon by cutting the string 
shorter!).

It is this same phenomenon of neutral buoyancy that we want to obtain in 
our soda. The problem is to design the jello. Soda is a particularly
difficult medium to work with because of those little bubbles; Floating
jello lumps in a still drink would be a lot easier to achieve. The
important things are

 The jello must be made of an approved food material
 The jello must be indefinitely stable in water -- it must not dissolve 
or get sticky
 The jello lumps must remain individual; they must not stick to one 
another or to the walls
 There is a need to consider how the bubbles interact with the jello 
lumps

In the context of this last point, there is a concept that surface chemists 
call the "hydrophilicity" (roughly Greek for water-loving-ness) that can be 
controlled for different effects. Jello lumps can be made water-repellent 
or water-attracting. Gas bubbles will readily adhere to water-repellent 
jello lumps, and carry them to the surface. A strongly water-attracting 
jello lump will be little affected by gas bubbles. We could make a product 
with slightly water-repellent jello lumps that were denser than water, so 
that they would sink to the bottom while the bottle remained closed. But 
when the bottle was opened, gas bubbles would cling to the jello lumps, 
lifting them to the surface, where they would lose their bubbles and start 
to sink again until they had enough bubbles to lift them again, and so on. 
Fine control would be needed though, because if the jello lumps were not 
heavy enough, or too water-repellent, they would simply spend all of their 
time sitting in a froth at the surface. The other way to go would be to use 
jello that was the same density as water, and extremely water-attracting, 
so that bubbles would not adhere to the surface of the lumps at all, and
you would have neutral buoyancy whether the bottle was opened or closed.

To stop the jello lumps from sticking to one another or to the walls, there
is another surface chemical trick. The conditions are arranged so that the 
jello gets a surface electrical charge in the soda solution. All lumps 
get the same charge, and like charges repel. If the charge is the same as 
that at the bottle walls, the lumps will also stay clear of the walls.