UCSB Science Line

Does blonde hair turn green in chlorinated water
because chlorine is green?
Question Date: 2003-12-18
Answer 1:
Any color hair can take on a greenish tinge
after a lot of exposure to swimming pool water,
it's just that the greenish tinge is easier to see
on light-colored hair than on dark-colored hair.
Chlorine is not green, and it's actually
not the chlorine that causes the color, although
the chlorine may help indirectly. Here's what I
mean by that:
The green color is caused by certain heavy
metals, mostly copper, that lodge in cracks
in the scaly outer covering of your hair shaft.
This outer covering is called the cuticle,
and it normally protects your hair. Swimming a lot
can damage your cuticle, allowing the copper and
other metals to get it and stick there. Once
there, they oxidize (kind of like rusting), and
oxidized copper is green. (Incidentally, that's
why the Statue of Liberty is green, and why old
pennies are sometimes green--the copper in them
has oxidized.) Chlorine's role in this is that it
helps damage your hair's cuticle. So, although the
green you see is not chlorine, the chlorine
probably helped the copper get in and stick there.
The copper then oxidizes, and voila! Green hair.
Answer 2:
Many people have experienced blonde hair going
green after prolonged exposure to chlorine in
swimming pools. Sometimes darker hair can also
develop a green tint to it. The problem is due to
high concentrations of copper compounds
dissolved in the pool water. This can
chemically interact with chlorine and the
resulting chemical compound readily binds to the
hair. It has also been reported that high levels
of copper in tap water can also turn hair green.
Chlorine in swimming pool water may affect the
general appearance of the hair. After a swim in
chlorinated water most people's hair looks very
dull and dry. This is usually due to removal of
oils that coat the hair to give it a shiny look
and certainly chlorine is a very powerful remover
of hair lipids.
So the short answer is, no, it is not because
chlorine is green. In fact, it is because the
copper compounds, which are also in pools, are
greenish. When that reacts with the chlorine it
can bind to hair causing it to look green. You can
see this for yourself... take a clean copper penny
and put it in a little chlorine bleach overnight
and see what happens! The penny needs to be shiny
clean, not dark looking. Also, please be sure
to do this with an adult because chlorine bleach
is a dangerous chemical.