Ask A Scientist© General Science Archive

name         Jessica L.
status       student
age          10

Question -   Hello,
I love playing with bubbles and I really like to know if I can produce
bubbles that are rectangular or even in the shape of a square. Can you
please help me?
----------------------
Jessica,

Ask a bookseller to track down the old paperback book -- "Soap Bubbles And
The Forces That Mold Them." It is excellent and it will direct you on
making bubbles of very exotic configurations. Good luck and have fun.

Regards,
ProfHoff 331
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Hi, Jessica !!

If I understand your question correctly, you
play with bubbles produced by blowing air
from the mouth through a pipe that was
before immersed in water with soap, is it ?

If that is the case, then I can assure you
that it is impossible to obtain another form.
The round form of a bubble is most stable
form among others; it  is the form of our planet,
the form of the Moon, of Venus, Mars, of
our Sun and of the stars.

The nature looks always for low levels of
energy and round is the less energetic form
of a bubble.



Alcir Grohmann
Beschaffung SAM
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You have chosen a fascinating subject for a hobby. The fundamental
principle of soap bubbles and soap films is: "They assume a surface of
minimum surface consistent with the boundary that constrains them."

For a single unconstrained soap film this is a sphere if there is no air
movement to disturb it. For two or more bubbles fused together, the relative
size of the bubbles will be that which makes the angle of contact between
the spherical bubble parts equal to 120 degrees -- it all comes out of the
physics -- this is the shape that forms a minimal surface for the collection
of two or more fused bubbles.

A "free" bubble will always be a sphere of part of a sphere. You can make
rectangular, cubical bubbles be suspending the bubble film on a wire frame
of the desired shape. In fact, this has "trick" has been used by physicists
to find the geometry of minimal surfaces if they need a "hint" about how to
treat the problem theoretically.

Three books you may find interesting are:
"Bubble-ology" published by Lawrence Hall of Science (has soap bubble
recipes and no math).

"Soap Bubbles: Their Colors and Forces that Mold them" by C. V. Boys (an
older book but for many years the classical book on the topic of bubbles --
somewhat more advanced in the math).

"The Science of Soap Films and Soap Bubbles" by Cyril Isenberg ( a more
mathematical treatment, but there are color pictures of soap films formed on
wire frames of different geometries ).

Most soap recipes call for glycerin. If you purchase this in a drug store it
is very expensive.
However, you can obtain it from a local farm and animal supply store very
inexpensively.

Have fun,

Vince Calder
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Dear Jessica:

I recommend that you find a copy of the book "Soap Bubbles" by Charles
V. Boys.  It is old (1958), but still available.  Chances are that you
can get it from a local library.  It captures the delight of these
wonderful objects, and it also deals with the science behind them.

Tom Douglas
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