 |
 |
Root Beer Foam
Name: Unknown
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993
Question:
A 9-year old boy would like to know why root beer foams so much
more than other soft drinks. He noticed that not only is there more foam, but
also that it takes longer to go away.
Replies:
You might want to check out an issue of Physics Today several
months back that discussed the foam in regular beer. I think in the case of
root beer they put stuff in to make it foam like real beer... The scientific
study of foam has only recently been underway, but brewers and other similar
types have been experimenting for years to get what they wanted - think of
shaving cream, for example, which was pretty much the way it is today without
much help from theoretical scientists, though certainly experimentalists were
involved. A foam is really a rather peculiar kind of material - it is formed
by a liquid with "surfactant" molecules in it, which lower the surface tension
so much that the liquid actually likes to be spread out over a really wide
area, and so you can whip or stir it up so that air gets into it, forming
millions of bubbles. Different types of foam have different sizes of these
bubbles, resulting in different overall stiffness (I guess there are maybe
other factors involved too). Eventually, gravity wins out and the liquid in
the bubbles gradually drains away. Also bubbles gradually merge, getting
bigger and bigger, and the foam loses its "foaminess" and disappears. These
different properties - the size of the bubbles, the surface tension and
complex molecules involved, and the effects of gravity, all combine to produce
the quite different collection of different types of foams around. But, I am
afraid I do not know the direct answer to why root-beer foams last longer.
You might want to check the different ingredients used.
A Smith
Click here to return to the Physics Archives
| |
Update: June 2012
|
|
