|Does dark hair retain more heat, or becomes hotter
than blond or fair hair when out in the sun?|
|Question Date: 2018-05-01|
Yes, dark hair does become hotter than blond
hair when out in the sun. To understand this,
you need to know two things about light.
The first thing you need to know is that
sunlight is actually the combination of many
different colors. You can see this by shining
light into a prism and watching all the colors of
the rainbow come out.
The second thing you need to know about light
is that the color that an object "looks" is the
colors of light that that object *reflects*.
Plants are green because they *reflect* green
light, and keep in all of the other colors.
White objects reflect all colors of light, and
black objects keep in all colors.
Putting these two facts together, dark hair
absorbs (keeps in) all colors of light, while
blond hair reflects all colors of light. Absorbing
more sunlight makes hair hotter, and therefore
dark hair will be hotter than blond hair in the
Before getting into the main part of the answer, I
should make the distinction between retaining
heat, and becoming hotter (absorbing heat).
The first can be thought of ashow much heat
energy can be contained, while the second is
how well heat is taken up. All else being
equal, dark-colored hair and light-colored hair
should be able to hold the same amount of heat
(as an analogy, dark- and light-colored clothes
coming out of the dryer will be the same
temperature), but dark hair will absorb more
heat when in the sun. How much energy a
substance can hold depends on the structure, and
therefore on how much and how many ways the
various atoms/molecules making up the substance
can vibrate/rotate/("jiggle"). (I suppose the
different colors will arise from different
molecules or structure, and that this would have
some effect, but the net difference is apparently
As for dark hair becoming hotter, the
reasoning is the same as for dark- vs.
light-colored anything else: dark-colored
things absorb more energy than light-colored
things. The reasoning really goes the other
way though, and it is that we have chosen to call
objects which do not reflect light (i.e. those
which absorb the light) as black, and those which
do reflect light (and the energy in it) as
lighter/white (some discussion
If you would like proof, unfortunately I was not
able to find good, scientific information for
humans, so hopefully the consideration of
springboks (a deer-like animal) is
acceptable. In these animals, those with black fur
experienced a greater and faster temperature rise.
Things with dark colors absorb (take in) all
light and turn it into heat. On the other
hand, things that are lighter in color absorb
some light but not all light.
For example, a red shirt reflects red-colored
light and a yellow shirt reflects yellow-colored
light. A white object, for instance a white box,
reflects all colors of light and therefore absorbs
the least heat of all the colors and stays cool
the longest. Black objects, by contrast, absorb
all colors of light and becomes hotter than
objects of any other color, so the answer is yes,
dark hair does become hotter than light-colored
Dark hair absorbs more heat. It also emits
more heat, so it will be cooler indoors to be
dark-haired and warmer out-doors to be
dark-haired. Still, it's better to just wear a hat
when spending much time outside.
Here's an experiment that should show how a light
colored house stays cooler in the summer than a
dark colored house:
house color heat
Darker colors tend to absorb more energy
from the sun than objects with lighter colors.
Someone wearing a white T-shirt in the summer
will find that he is cooler than someone wearing a
black or dark-colored shirt. This is true of all
materials which have dark colors. Other dark
surfaces include blacktops, paved roads or
materials absorb energy
Click Here to return to the search form.
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.