Children's hair mysteriously darkens; Why some candles burn fast
Q: When I was born, I had blond hair, but now it is dark
brown. What caused this change? Eric, Farmington, Missouri, USA
 Blond
boy whose light, almost white hair color will probably darken. Photo courtesy of
Nino Barbieri and Wikipedia.
A: "Light hair, as a rule, has a tendency to darken during childhood, says
geneticist
Rick
Sturm, principal research fellow at the University of Queensland in
Australia.
Hair darkens because genes that control hair color switch on.
The more pigment produced in the hair follicle, the darker the hair.
Much pigment results in dark brown hair; little pigment causes blond hair.
Sometime during your childhood, the genes* controlling
hair color changed, and told the pigment
protein to produce much pigment. Your hair consequently gradually turned to dark brown.
It's an 'on' / 'off' order, like switching on a light.
We don't, however, have a clue why the genes changed. They just
do for many children.
We strongly suspect genes control the timing of the change. In 1975,
two pediatricians (Adam P. Matheny Jr. and Anne Brown Dolan of the University
of Louisville School of Medicine) examined the hair color of identical twins
(169 female twins and 161 male) routinely from the time the twins were six
months old until they were six years old.
They found marked changes in the hair color for both sexes. Moreover,
they discovered a "high rate" of agreement at every age "in spite of the general
change in hair color." Both twins' hair color changed, beginning at about
the same age and continuing at nearly the same rate. They, therefore,
concluded that genes influenced the timing of color changes.
In addition to hair darkening during childhood, "there are changes [causing
hair to darken] also apparent at puberty that would likely be hormone related,"
says Sturm. The darkening can continue past puberty into the 30's and
40's.
By the way, the hair of some herd animals (for example, giraffes) darkens, but
not with age. "The top male's hair darkens when he takes the alpha
position," says Sturm, who suspects hormonal changes (maybe testosterone).
"The specific example I have seen was a group of giraffes where the
alpha male had noticeably darker spots. The keepers told me that this
changed over time as the alpha male position was handed on. And it happens in other animals."
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*Genes controlling hair color include:
tyrosinase,TYRP1, MATP, SLC24A5, SILV and OCA2
Further Reading:
Sex and genetic differences in hair color changes during early childhood,
University of Louisville School of Medicine, 1975.
Hair color,
Wikipedia
Understanding genetics, hair color, Stanford University
Q: Does the color of a candle determine whether it
will burn faster? Is there some ingredient that makes it burn faster?
Jason, Avilla, Indiana, USA
A red candle burns at the same speed as a yellow one. Photo courtesy of
Matthew Bowden and Wikipedia.
Color makes no difference how fast a candle burns. "Black candles burn no faster than white," says
chandler
Stefan
Phillips of the Island Candle Company.
Wick size is the primary factor determining candle-burning rate. "A larger
wick is like stepping on the gas pedal," says Phillips. The big wick delivers
more fuel to the burning flame.
By the way, a candle is a cylinder
of solid fuel — paraffin wax — that surrounds a wick. How does it burn? Bringing a lit match to a
wick melts and then vaporizes the wax coating the wick. The wax vapor combines
with oxygen, and burns.
Wax is the most important ingredient that makes a candle burn faster. Soft wax has a higher oil content and lower melt temperature; therefore,
it burns faster.
Typically, candles in jars have soft wax, and pillar candles have hard wax.
The longest burning candles are pillar candles made of a blend of beeswax and
paraffin.
Burning tips (from the Island Candle Company)
- Trim your wick to 1/4 inch or less before you light a candle.
Long wicks burn inefficiently and may smoke.
- Protect your candle from drafts, which can blow the flame to one
side, and cause molten wax to run down the side
of the candle. A dancing candle flame indicates a shortened candle life.
- After snuffing out the candle, straighten the curled wick with a toothpick
while the wax is soft. A candle with a straight wick burns better and
lasts longer.
Further Reading:
Why a candle flame goes up, WonderQuest
If you place a lighted candle in a sealed jar and drop it,
why does the candle go out when someone catches the jar? WonderQuest
Tips
for taking care of candles: a burning guide, Island Candle Company
Candle burning, Newton ask a scientist
Readers' answers to question of the month:
- Actually what makes a candle burn faster then others is the type of wick
that you use. Sometimes pigment from dyes clog a wick which can effect the
burn time but, more often then not this is not the reason. Wicks are the burn
time.
Debi B., Ohio, USA
Next month's question:
Why
do people only snore when they are asleep? You breathe all the time, but
it's noisier when you are fast asleep. Why?
I'll publish the best answers, and you get credit. Click here:
Answer-the-question
to give me your answer.
(Answered April 30, 2007)
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