Two weeks ago, I took my car
out to get our weekly groceries. I noticed a tiny, about half an inch crack in
the windscreen right at the bottom on the driver’s side. It did not seem serious,
and it was not in my field of vision. I did not worry much.
After the shopping when I was
back home, I noticed the crack had gone a bit longer. In the evening we went for dinner to a
friend’s house who lived in about 30 miles away. Next morning, I noticed the
crack has become much longer, about 15 inches.
I did not go over any big pothole in the night, did not hit anything, how
did the crack get so big?
I had read about them in a magazine only last week. When molten glass is dropped in a bucket of cold water it forms a tear drop shape with a slender curved tail, like a human sperm. The head is so strong that it cannot be broken even when struck with a bullet. But a tiny twist or tinkle on the tail can easily break not only the tail but also shatters the head into tiny pieces. https://youtu.be/24q80ReMyq0
Rupert of Rhine presented some to king Charles II of England. He was very intrigued with their unique property and asked the newly constructed Royal Society for finding the scientific basis behind the phenomenon. The riddle has taken almost 400 years to unravel the physics behind it with the help of scientists from all over the world.
I panicked, at once rang my
car insurance company. The lady was very calm, she said “not to worry, the
glass pane will not break into pieces as it was made of laminated glass. She will
send the glass engineer who will fix it.” When? I asked. she checked and rang back; the earliest date
was 3 days later.
I did
not dare to drive the car for the next 3 days till the Autoglass engineer came.
After examining my windscreen, he
explained that there was a small chip in the glass right at the beginning of
the crack. It was caused by a loose gravel on the road surface. These small,
shallow craters are quite common and can be easily repaired at that stage. But
if not repaired, cracks get bigger with vibrations in the glass when one drives
the car. Once large cracks appear the whole windscreen must be replaced, which
was the case with my car.
How long it will take to
replace the wind screen? I asked thinking it may take a few days. He said that
he would do it here and now. It would take about an hour and a half.
He rang me later to say that
he has finished, and I should come down to check it. I did. it looked good and
everything worked. I thanked him
profusely.
Though the shattering of the Rupert’s
teardrops caused me to panic, if I would have researched a bit more, I would
have also known that initial early Royal Society studies on the ‘Drops’ did result
in development of shatter resistant, tempered glass which was patented in as
early as 1874!
1. On the extraordinary
strength of Prince Rupert's drops
H. Aben; J. Anton; M. Õis; K.
Viswanathan; S. Chandrasekar; M. M. Chaudhri
Appl. Phys. Lett. 109, 231903
(2016)
