Like every Friday, the weekly corner "A Taste of Physics" is back — this time for edition number 50 💫
This week: the physics of glass, plus a few words to mark the 50th edition.
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Ordinary glass is called soda-lime glass. It is typically silica-based and tends to shatter when exposed to high heat.
The reason is that when heat strikes one side of the glass it causes that side to expand rapidly, while the cooler side remains at its original volume.
These size differences create micro-cracks on the glass surface, which propagate quickly through the material and shatter it.
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Heat-resistant glass — borosilicate glass — has a chemical composition specifically designed to inhibit these processes, giving it heat resistance of up to several hundred degrees.
The element boron is added to the standard chemical composition of glass, providing a dual benefit for heat resistance.
Boron's primary advantage is a reduction in thermal expansion — the glass volume increases less as temperature rises.
An additional, though more minor, benefit is improved heat distribution within the glass: heat travels from one side to the other more quickly, thereby preventing the temperature differentials that cause cracks to form.
Had the person in the video made his glass bricks this way, they would likely have survived exposure to fire without any damage.
This type of glass can also be found in some remarkable places — such as the lens of the Hubble Space Telescope.
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Tempered glass is glass whose manufacturing process gives it great strength against impact.
During production, the glass is heated to nearly 700 degrees, at which point it becomes a uniform-temperature molten mass.
In the next stage, the surfaces of the glass are cooled very rapidly using jets of air, so that the outer surfaces cool, contract, and harden while the interior is still extremely hot.
As the interior of the glass cools and its volume shrinks, it pulls the outer surfaces inward, creating a very tight bond between the glass molecules.
Because the surfaces are very hard, they are more resistant to external stress, which prevents the formation of the initial micro-cracks in the event of a sudden impact.
Ballistic-resistant glazing is created by combining multiple layers of tempered glass with polymer interlayers — such as polycarbonate — between each pane.
Such glazing protects military vehicles in combat zones.
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This manufacturing process has one further advantage.
The high internal stresses mean that if the glass does shatter, it breaks into thousands of harmless small fragments rather than large, dangerous shards.
This is why automotive glass is made this way — it provides heat resistance together with greater safety in the event of an accident.
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In honor of edition 50, here is a small change:
Starting next week, the corner will evolve from "A Taste of Physics" to "A Taste of Science for the Weekend."
This minor change will allow the corner to cover fascinating topics from other branches of science, not just physics.
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The background research for this corner is my weekly quality time, and it lets me share what I believe makes life so interesting — curiosity, science, and sound reasoning.
A heartfelt thank you for the thoughtful comments and warm words you leave in the replies; they are what give this corner its reason to exist.
Shabbat Shalom 😊
#taste_of_physics #taste_of_science_for_the_weekend