4.5 (90%) 2 votes
Today I found something new and interesting for you, although it may be new only for me, but it will definitely be interesting for everyone - drops of Prince Rupert. Let's figure out what these drops are and why they are interesting ...
Prince Rupert drops are glass drops with a thin tail, which are the result of placing molten glass in water. And the interesting thing about them is that it is almost impossible to crush, trample, smash or destroy them in any other way available to people, but this only applies to the drop itself, but it also has a thin tail, in which the vulnerability of a seemingly indestructible thing is hidden, and if it break, then there is a real glass explosion. See for yourself how they unsuccessfully try to crush the drop of Prince Rupert with a hydraulic press:
and how it easily explodes when the thin tip is damaged:
Well, what an interesting effect?
Let's see how such an interesting result is obtained? To do this, you need to understand how drops of Prince Rupert are obtained.
In order to make drops of Prince Rupert, molten glass must be placed in water. When molten glass enters cold water, it solidifies very quickly with a simultaneous accumulation of enormous internal stress. Moreover, cooling occurs at least quickly, but not instantly, therefore, when the surface layer has already cooled down, solidified and decreased in volume, the inner part of the drop, let's call it the core, is still in a liquid and molten state.
Further, the core begins to cool and shrink, but intermolecular bonds with the already solid outer layer prevent it from shrinking, as a result of which, after cooling, the core occupies a larger volume than if it were cooled in free form.
Because of this, forces with the opposite direction act on the boundary of the outer layer and the core, which pull the outer layer inward and the core outward and create, respectively, a compressive stress for the outer layer and a tensile stress for the inner core. As a result, we have a huge internal stress, which makes the drop very strong, but at the same time, any damage to the outer layer leads to a violation of the structure and a glass explosion, but since the thinnest place is the tail, it is through it that the outer layer can be destroyed in order to to get such a beautiful explosion as in the video above or in the photo below:
And this video is for those who find it easier to perceive video information than to read a lot of letters:
The drops of Prince Rupert were first discovered in Germany in 1625, but how often there was an opinion that they were discovered by the Dutch, or maybe it sounded more beautiful, because everything foreign causes more curiosity, these times do not change, hence the second name for these drops - Dutch tears.
And here Prince Rupert asks the reader? The fact is that Prince Rupert, the British duke, was the person who brought these drops to England and presented them to the English monarch Charles II. The king really liked the interesting glass drops and he gave them to the British Royal Scientific Society for study. In honor of these events, curious drops began to be called the drops of Prince Rupert, and this name has been perfectly preserved to this day. Here it is a vivid example of how you can go down in history simply by giving an interesting thing to the right person.
Interestingly, the method of making Dutch tears was kept secret for a long time, while at the same time they were sold as interesting toys at fairs and markets.
I read what they write about Prince Rupert. His biography is quite interesting, he was involved in a large number of historical events, but this is rather a topic for a separate post.
When I finished the post, I found an interesting and relevant video on the topic, in which the whole process is shown from the beginning to the end - from the creation of Prince Rupert's drop to a glass explosion:
Now the topic of Prince Rupert's drop is fully disclosed and you can safely show off this knowledge in the company or even make such drops (just be careful). That's all for today, see you soon!
Batavian tears or Bologna flasks, as well as drops of Prince Rupert, are hardened drops of tempered glass with extremely durable properties. They were brought to England by Prince Rupert of the Palatinate in the middle of the 17th century. At the same time, they attracted the close attention of scientists.
17095 1 4 18
Most likely, such glass drops were known to glassblowers from time immemorial, but they attracted the attention of scientists rather late: somewhere in the middle of the 17th century. They appeared in Europe (according to various sources, in Holland, Denmark or Germany). The technology for making "tears" was kept secret, but it turned out to be very simple.
If you drop molten glass into cold water, you get a tadpole-shaped drop with a long, curved tail. At the same time, the drop has exceptional strength: its “head” can be hit with a hammer, and it will not break. But if you break the tail, the drop instantly shatters into small fragments.
The frames recorded using high-speed photography show that the “explosion” front moves drop by drop at a high speed: 1.2 km/s, which is almost 4 times higher than the speed of sound.
As a result of rapid cooling, the glass drop experiences strong internal stresses, which causes such strange properties. The outer layer of the drop cools so quickly that the glass structure does not have time to rebuild. The core is stretched, and the outer layer is compressed. Similarly, tempered glass is obtained - however, it does not have that tail, for which it is possible to break the shell so easily.
The English nobility of the 17th century was reputed to be inquisitive and did not shy away from science. King Charles II even died of his passion for alchemy: already in our time, mercury was found in his hair in a concentration incompatible with life. The cousin of Charles II, Prince Rupert, was famous for his passion for scientific curiosities, both theoretical and practical.
This Prince Rupert, also known as Duke Ruprecht von der Palatinate, brought to London glass castings in the form of drops with long twisted tails. Presenting them as a gift to the king, Rupert said that this is a recent German invention, and that the strength of glass drops exceeds that of steel.
Rupert hid the method of production from the king, citing ignorance. Although now we understand: the prince was silent solely for the sake of greater mystery ...
Charles II gave the received drops for analysis to the Royal Scientific Society. From that moment on, the glory of Rupert's drops began.
The strength of Rupert's glass drops was, however, uneven. If the head of the drop could withstand any blow, the tail - especially the tip of the tail - was highly vulnerable. The strangest thing is that the destruction of the tail led to the instant disintegration of the entire glass casting! Moreover, explosive disintegration, with an instantaneous scattering of the smallest fragments!
Members of the Royal Scientific Society sent letters inquiring about the nature of unusual glass to all available limits. The popularity of an unusual toy among the London nobility began to grow. Prince Rupert made a good business of selling amazing glass drops for a high price, then strengthening ties with interesting gifts.
Soon the situation began to clear up ...
According to information received from the Dutch, the Danes began to play with Rupert's drops before the Germans - but the secret of making durable glass castings came to Denmark from Italy. The entire south of Europe knows them as "Bologna flasks" and sees nothing difficult in making drops from glass.
After a series of experiments, the scientists of the Royal Society of London determined: in order to obtain the most successful drops of Rupert, the glass should be taken as clean as possible, and heated no higher than to the degree of complete softening - otherwise the drop falling into the water is covered with cracks.
Satisfied with that...
Rapid cooling of a glass drop in a medium that effectively lowers the temperature leads to compaction of the outer layers of the body, compression of the array with simultaneous stretching of the still hot core of the casting.
The strength of Rupert's drop is not at all unlimited, and only four times the strength of glass produced using conventional technologies. However, strength indicators are highly dependent on the composition of the glass charge, and dense quartz glass in tempered and drop form is indeed able to withstand the blows of a blacksmith's hammer.
But only if you do not hit the thin, fragile tail of Rupert's drop!
That is why, by the way, in ancient Europe, a drop of Rupert is pleased to quickly migrate from the category of funny curiosities to the category of dangerous entertainment.
Modern experimenters do not stop experiments with Rupert's drops. Particularly spectacular are attempts to destroy glass drops with a shot from a rifle. A soft lead bullet hits the head of Rupert's drop with a force much greater than that of a blacksmith's hammer, but the bullet cannot break the tempered glass.
The shock wave arising in the glass mass proves to be fatal for the thin tail of the Rupert drop. When an oscillatory pulse passes through thin glass, rapidly expanding cracks are created. At a speed of more than 1 km / s, cracks grow throughout the body of the drop, multiply, expand and actually explode the glass.
The bluish-red flashes of triboluminescence of the decaying drop of Rupert are the essence of the glow of atoms of atmospheric gases, excited by weak electric discharges. Molecules generate electricity
), or "Danish tears". The drop head is incredibly strong, it is very difficult to mechanically damage it by compression: even strong hammer blows or a hydraulic press do no harm to it. But it is worth slightly breaking the fragile tail, and the whole drop will shatter into small fragments in the blink of an eye.
This curious property of a glass drop was first discovered in the 17th century, either in Denmark, or in Holland (hence another name for them - Batavian tears), or in Germany (sources are contradictory), and an unusual little thing quickly spread throughout Europe as a funny toy . The drop got its name in honor of the commander-in-chief of the English royal cavalry, Rupert of the Palatinate, popularly known as Prince Rupert. In 1660, Rupert of the Palatinate returned to England after a long exile and brought with him unusual glass drops, which he presented to Charles II, who transferred them to the Royal Society of London for research.
The technology for making the drop was kept secret for a long time, but in the end it turned out to be very simple: just drop molten glass into a bucket of cold water. In this simple technology lies the secret of the strength and weakness of the drop. The outer layer of glass solidifies quickly, decreases in volume and begins to put pressure on the still liquid core. When the inner part also cools, the core begins to shrink, but this is now counteracted by the already frozen outer layer. With the help of intermolecular forces of attraction, it holds the cooled core, which is now forced to occupy a larger volume than if it had cooled freely. As a result, opposing forces arise at the boundary between the outer and inner layers, which pull the outer layer inward, and a compressive stress is formed in it, and the inner core outward, forming a tensile stress. In this case, the inner part can even break away from the outer, and then a bubble forms in the drop. This opposition makes the drop stronger than steel. But if, nevertheless, its surface is damaged by breaking the outer layer, the latent force of tension will be released, and a rapid wave of destruction will sweep from the place of damage along the entire drop. The speed of this wave is 1.5 km/s, which is five times faster than the speed of sound in the Earth's atmosphere.
The same principle underlies the manufacture of tempered glass, which is used, for example, in vehicles. In addition to increased strength, such glass has a serious safety advantage: when damaged, it breaks into many small pieces with blunt edges. Ordinary “raw” glass shatters into large sharp fragments that can seriously injure you. Tempered glass in the automotive industry is used for side and rear windows. The windshield for cars is made multi-layered (triplex): two or more layers are glued together with a polymer film, which, upon impact, holds the fragments and prevents them from flying apart.
Veronika Samotskaya
Prince Rupert's tear, Batavian or Dutch drops, devil's tear are all names for the same physical phenomenon. The round part of such a tear is heavy-duty glass, and its tail is its Achilles' heel, which, breaking off, turns the entire structure into dust.
Opinions regarding the origin of Prince Rupert's drops are very diverse. Some sources indicate that they were invented in 1625 in Germany. But they are also called "Batavian tears" and here's why.
It is believed that glass is a rather fragile material. But the property of these glass drops is such that even with numerous hammer blows on the rounded part, they do not break. At the same time, if during the experiment this drop is placed under a press on a metal plate, then a drop-like imprint will remain on it. But one has only to break the tip of her thin tail, and she instantly explodes into a million tiny fragments.
A very strong stress arises between the shell and the core, respectively - compression on the outer layer and tension on the inner one. If you lower the molten glass into too cold water, then the voltage level will reach a maximum and allow the inside of the drop to separate from the outside, forming a bubble.
It is the internal forces of compressive and tensile stress that resist any impact force. By breaking off the “tail” of the drop, we will destroy the top layer, which will allow the internal tensile pressure to work to its full potential, and the glass drop will be blown to dust. This internal stress is so great that the explosion occurs literally in one moment. Therefore, when conducting an experiment, be sure to stock up on goggles.
Recently, a group of scientists from different parts of the world set out to “get to the bottom” of the truth and find out why and how exactly the explosion occurs when the tail of Prince Rupert’s drop breaks off.
The fact is that when the outer shell is damaged, a crack appears that penetrates directly into the “heart” of the drop, where the same stress force is concentrated.
The researchers also found that in order for a drop of Prince Rupert to explode, it is required that the cracks reach its center. Upon hammer blows or any other impact on the drop head, cracks disperse over its surface without penetrating into the internal tension zone. This is what explains the strength of the ball. When the “tail” is destroyed, the cracks manage to penetrate into the inner part of the glass tear, which entails an explosion.
Auto glass is made on a similar principle today. In addition to being more durable, it has another important benefit for the safety of passengers - in case of damage, it crumbles into small pieces with rounded edges. Raw glass breaks, forming sharp and large fragments that can seriously injure.
Side and rear windows are made from tempered glass, while windshields are made by gluing several layers of such glass with a special polymer film, which in the event of an accident will prevent them from flying apart at all.
