The English nobility of the 17th century were reputed to be inquisitive and did not shy away from science. King Charles II even died from his passion for alchemy: already in our time, mercury was discovered in his hair in a concentration incompatible with life. Charles II's cousin, Prince Rupert, was famous for his passion for scientific wonders, both theoretical and practical.
It was this Prince Rupert, also known as Duke Ruprecht von der Pfalz, who brought drop-shaped glass castings with long curved tails to London. Presenting them as a gift to the king, Rupert said that this was a recent German invention, and that the strength of glass drops exceeded the strength of steel.
Rupert hid the production method from the king, citing ignorance. Although now we understand: the prince was silent solely for the sake of greater mystery...
Charles II gave the resulting drops for analysis to the Royal Scientific Society. From that moment on, the glory of Rupert's drops began.
Properties of Rupert's Drop
The strength of unprecedented glass surprised English scientists. Rupert's drop withstood even the blow of a burly blacksmith, and dents remained on the steel of the anvil and hammer. Can glass have such hardness and strength? - the court scientists marveled. 
The strength of Rupert's glass drops was, however, uneven. While 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, it will decay explosively, with the instantaneous scattering of the smallest fragments!
Members of the Royal Scientific Society sent letters asking about the nature of the unusual glass to all available areas. The popularity of the unusual toy among the London nobility began to grow. Prince Rupert made a good business, either selling amazing glass drops at a high price, or strengthening ties with interesting gifts.
Soon the situation began to become clearer...
Rupert's Drops come from...?
The prince never insisted on his authorship of the funny trinket, and attributed the credit for the invention of glass drops to German artisans. It turned out, however, that in nearby Holland such curiosities have been known for a long time - they know them and do them for the amusement of the public. Moreover, the Dutch carry drops of glass around the world, and everywhere they are called “Batavian tears”, named after the Batavia shipyard on the shores of the Zuiderzee Bay. 
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 “Bolognese flasks” and sees nothing complicated in making glass drops.
Rupert's Drops are easy!
To obtain drops of a characteristic shape and unprecedented strength, glassmakers reported, glass heated enough to fluid viscosity should be dropped into a container with cold water. The hardened casting is the Bolognese flask, also known as Rupert's drop - from the point of view of serious artisans, an empty trifle and a transfer of expensive material. 
After conducting a series of experiments, scientists of the Royal Society of London determined: to obtain the most successful Rupert's drops, glass should be taken as clean as possible, and heated no higher than to the degree of complete softening - otherwise a drop falling into the water will become covered with cracks.
We were satisfied with that...
A modern take on Rupert's drops
Physics explains the appearance of Rupert's drops as a result of the long-known tempering - a technology widely applicable to steel products, but in this case it concerns glass. Amorphous in structure, semi-liquid glass hardens without crystallization, but with a decrease in volume. 
Rapid cooling of a glass drop in an environment that effectively lowers the temperature leads to compaction of the outer layers of the body, compression of the mass with simultaneous stretching of the still hot core of the casting.
The strength of Rupert's drop is not at all infinite, and is only four times stronger than glass produced using conventional technologies. However, strength indicators strongly depend on the composition of the glass charge, and dense quartz glass in tempered and droplet form is really capable of withstanding the blows of a forging hammer.
But only if you don’t hit Rupert’s drops on the thin, fragile tail!
Break Rupert's Drop
Breaking Rupert's drop is not difficult. If you break off, beat off, shoot off the thin glass tail of a Rupert drop, it all instantly scatters almost like dust! Moreover, the speed and distance of scattering of the smallest fragments of a drop are such that the danger of damage to the skin and eyes of the observer is very real. 
That is why, by the way, in ancient Europe, Rupert's drop of content quickly migrated from the category of amusing curiosities to the category of dangerous entertainment.
Modern experimenters do not stop experiments with Rupert's drops. Particularly spectacular are attempts to destroy glass droplets with a rifle shot. A soft lead bullet hits the head of Rupert's drop with a force significantly greater than the force of a blacksmith's hammer, but the bullet is unable to break the tempered glass.
The shock wave arising in the glass mass turns out to be destructive for the thin tail of Rupert's drop. When the vibration pulse passes through thin glass, rapidly expanding cracks appear. At a speed of more than 1 km/s, the cracks grow throughout the droplet body, multiply, expand and actually explode the glass.
Explosive glow of Rupert's drop
Particularly interesting is the flash of light that accompanies the wave of disintegration of tempered glass. This kind of glow phenomenon is called triboluminescence. Triboluminescence, in contrast to the usual luminescence, occurs not in the bulk of the material, but in the boundary environment.The bluish-red flashes of triboluminescence of the disintegrating Rupert drop are the glow of atoms of atmospheric gases excited by weak electrical discharges. Electricity is generated by molecules
Prince Rupert's tear, Batavian or Dutch drops, the devil's tear - all these are names for the same physical phenomenon. The round part of such a tear is super-strong glass, and its tail is its Achilles heel, which, when broken, turns the entire structure into dust.
Opinions regarding the origin of Prince Rupert's drops vary widely. Some sources indicate that they were invented in 1625 in Germany. But they are also called “Batavian tears” and here’s why.
How the Prince Rupert Drop was discovered
Once in Holland, a scientist unfamiliar to us conducted some interesting experiment. He melted a glass stick on a powerful burner, and shook the liquid molten droplets into a container with ordinary water. Glass drops, freezing in cold water, acquired a bizarre shape, reminiscent of tadpoles with a round head and a thin snake-like tail. The discovery impressed the researcher, and he gave his discovery a name - Batavian Tears in honor of Batavia - the former name of his homeland. As it turned out, the scientist’s discovery did not stop there, because later he discovered their most interesting property.It is believed that glass is a fairly fragile material. But the property of these glass drops is such that even with numerous blows with a hammer on the rounded part, they do not break. Moreover, if during the experiment you place this drop under a press on a metal plate, then a drop-shaped imprint will remain on it. But as soon as you break the tip of its thin tail, it instantly explodes into a million tiny fragments.
One way or another, the Batavian Tears became widely known after the British Duke Rupert of Palestine presented them as a strange gift to the King of Great Britain, Charles II. The king then commissioned the Royal Scientific Society to investigate their mysterious and amusing nature. In honor of the Prince of Palestine, the Batavian tears began to be called nothing less than the glass drops of Prince Rupert. The method of their creation was kept in the strictest secrecy for a long time, but anyone could buy them as a funny souvenir.
Why does Prince Rupert's drop explode?
Today, the reasons for the unusual behavior of glass droplets have already been scientifically proven. The fact is that when glass drops get into cold water, they quickly freeze. High mechanical stress is generated inside each of them. If you imagine that a drop consists of a shell and a core, you can understand that it begins to solidify first at the surface, that is, its shell decreases and contracts while the core continues to be hot and liquid.
When the internal temperature of the drop decreases, the core also begins to compress, but now resistance arises due to the outer frozen layer. Close intermolecular bonds allow it to compress the nucleus, which already occupies a larger volume.
A very strong tension arises between the shell and the core, respectively - compression on the outer layer and tension on the inner. If molten glass is placed in water that is too cold, 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 compression and tension 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 in full force, and the glass drop will be blown to dust. This internal tension is so great that the explosion occurs literally in an instant. Therefore, when conducting an experiment, be sure to stock up on safety glasses.
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 an explosion occurs when the tail of the Prince Rupert Drop breaks off.
The fact is that when the outer shell is damaged, a crack appears, penetrating directly into the “heart” of the drop, where that same stress force is concentrated.
Bearing in mind the scientifically proven fact that the outer layer is compressed and the inner layer is stretched, scientists looked at how exactly the pressure is distributed inside the tear. It turned out that the compression force at the outer shell exceeds atmospheric pressure 7000 times and reaches 700 megapascals. This is incredible, considering that the surface of a glass tear is unusually thin and its area is only 10% of the entire body of the drop.
The researchers also found that in order for the Prince Rupert Drop to explode, cracks must reach its center. When struck with a hammer 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.
A modern application of the Prince Rupert drop effect
The principle of behavior of the Prince Rupert drop has already been successfully applied in industry. This type of glass is familiar to everyone as “tempered”.Previously, “tempered glasses” were produced. They could be dropped on the floor without a twinge of conscience - it never broke on impact. But a chip that accidentally appeared on the edge could provoke its explosion at any time. Therefore, such dishes had to be handled even more carefully than ordinary glass.
Automotive glass is made using a similar principle today. In addition to being more durable, it has another important advantage for passenger safety - if damaged, it crumbles into small pieces with rounded edges. When wet glass breaks, it forms sharp and large fragments that can cause serious injury.
Side and rear windows are made from tempered glass, while windshields are made by gluing several layers of such glass using a special polymer film, which will prevent them from flying apart in the event of an accident.
Video about the Prince Rupert drop effect
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Today I found something new and interesting for you, although perhaps it’s new only for me, but it will definitely be interesting for everyone - Prince Rupert’s drops. Let's figure out what these drops are and why they are interesting...
What are Prince Rupert Drops
Prince Rupert Drops are glass drops with a thin tail that are created by placing molten glass in water. And the interesting thing about them is that they are almost impossible to crush, trample, break or destroy in any other way accessible to people, but this applies only 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 a real glass explosion occurs. See for yourself how they unsuccessfully try to crush Prince Rupert’s drop with a hydraulic press:
and how it easily explodes if the thin tip is damaged:
Well, an interesting effect?
Let's figure out how such an interesting result is obtained? To do this, you need to understand how Prince Rupert's drops are made.
Prince Rupert drops how to make
In order to make Prince Rupert drops, you need to place molten glass in water. When molten glass enters cold water, it hardens very quickly with the simultaneous accumulation of enormous internal stress. Moreover, cooling occurs at least quickly, but not instantly, so when the surface layer has already cooled, hardened and decreased in volume, the inner part of the drop, let’s call it the core, is still in a liquid and molten state.
Next, the core begins to cool and contract, but intermolecular bonds with the outer, already solid layer prevent it from compressing, as a result of which, after cooling, the core occupies a larger volume than if it were cooled in a free form.
Because of this, forces act in the opposite direction at the boundary of the outer layer and the core, which pull the outer layer inward and the core outward, creating, respectively, a compressive stress for the outer layer and a tensile stress for the inner core. As a result, we have a huge internal tension, which makes the drop very strong, but at the same time, any damage to the outer layer leads to a breakdown of the structure and a glass explosion, and 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:
When and where were Prince Rupert's drops discovered?
Prince Rupert's drops were first discovered in Germany in 1625, however, as often happens, there was an opinion that they were discovered by the Dutch, or maybe it sounded more beautiful, because everything foreign arouses more curiosity, in this times do not change, hence the second name for these drops - Dutch tears.
What does Prince Rupert have to do with this, the reader may ask? The fact is that Prince Rupert, the British Duke, was the man who brought these drops to England and presented them to the English monarch Charles II. The king really liked the interesting glass drops and gave them to the British Royal Scientific Society for study. In honor of these events, the curious drops began to be called Prince Rupert's drops, and this name has been perfectly preserved to this day. Here he 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 selling them 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 was finishing the post, I found an interesting and relevant video, in which the entire process is shown from beginning to end - from the creation of Prince Rupert’s drop to the glass explosion:
Now the topic of Prince Rupert’s drop is completely covered and you can calmly show off this knowledge in company or even make similar drops (just be careful). That's all for today, see you next time!
Prince Rupert's Drop
This is one of the interesting properties of glass, which is popularly called “Prince Rupert's drops” (also known as Rupert's balls or Dutch tears).
Making a Prince Rupert drop is very easy. Simply take hot glass and drop it into a bucket of water. As the water quickly cools the outer surface of the glass, the temperature inside remains significantly high. When the inside of the glass finally cools, it shrinks inside the already hard outer shell. This creates a lot of tension.
Interestingly, the drop has amazing strength. The strength is simply amazing:
Yes, by breaking its tail, you will cause instant explosive destruction, similar to what causes the explosion of any glass product that was not placed in an annealing furnace after casting - simply by breaking the tail you start this process yourself.
Unlike ordinary glass, this drop cannot be broken even by hitting it very hard with a hammer - if you hit the main part of the “drop”. At the same time, if the “tail” of a tear is slightly damaged, it explodes like a grenade - but this can only be seen with a camera capable of filming at a speed of 100,000 frames per second. This is exactly what you can see:
The speed of the fault is approximately 4 thousand 200 km per hour.
Prince Rupert, cousin of King Charles II, had about as many titles as he had natural talents: Count Palatine of the Rhine, Duke of Bavaria, Earl of Holderness, Duke of Cumberland, part-time cavalryman, sailor, scientist, administrator and artist.
His father, Friedrich von Palatinate, was king of the Czech Republic for exactly one winter, and spent his entire subsequent life in Holland. Even as a child, Rupert mastered the main European languages, demonstrated good mathematical abilities and a talent for drawing. Rupert began his military career at the age of 14, accompanying the Prince of Orange at the siege of Rinberg. Two years later, during the invasion of Brabant, he entered the service of the prince's guard, and the next year, together with his older brother, visited English relatives, making an extremely favorable impression on Charles the First. From this trip he returned with an honorary Master of Arts degree, awarded to the distinguished guest at Oxford.
In 1637, Rupert took part in the siege of Breda, after which, together with his brother and a detachment of Scottish mercenaries, he went to fight in Westphalia, where in the fall of 1638 he was captured. He languished in prison until 1641, and at that time Lord Arundel, the English ambassador in Vienna, gave the prince a dog, which later gained great fame.
It was a white poodle, allegedly smuggled from Turkey, where the Sultan had prohibited foreigners from purchasing dogs of this breed. “It was extremely interesting to watch how this impudent and restless man amused himself by teaching a dog a discipline that he himself had never known.” The poodle, who received the simple nickname Boy, invariably accompanied Rupert until his death at the Battle of Marston Moor. The poodle was fondly remembered in the pamphlets of the "Roundheads", for example, in one engraving he is depicted growling at members of Parliament, dissolved by Cromwell. Boy enjoyed many privileges - he slept in his master's bed, used the services of more barbers than Rupert himself, and received the most tidbits from the hands of King Charles, who condescendingly allowed Boy to sit in his chair. According to rumors, the dog was very smart. So, at the word “Karl” he began to jump joyfully and loved to listen to the liturgy, turning his face towards the altar. This, obviously, gave rise to rumors that a spirit follows Rupert in the form of Boy, saying that the dog can become invisible and participates in necromancy sessions conducted by its owner. And the poor fellow was killed. The fight, as they say, was a silver bullet.
Back to the Prince In addition to training Boy during his years of imprisonment, Rupert also held theological conversations with confessors, resisting attempts to convert him to Catholicism, improved his skills as an engraver, read books on the art of war, and began an affair with the governor’s daughter. Thanks to the efforts of Charles the First, Rupert received his freedom on the condition that he would never again turn arms against the emperor. In August 1642, the prince and his younger brother Moritz arrived in England at the head of a detachment of English and Scottish veterans of the continental wars to act on the side of the king in the civil war with Parliament. Awarded the Order of the Garter, Rupert stood at the head of the royal cavalry, but soon the joy of his arrival became far from universal.
Although Rupert was an experienced soldier, he was characterized by youthful ardor, which, along with his foreign manners, repelled the king's respectable advisers. In particular, their understandable discontent was caused by the prince’s statement that he wanted to receive orders exclusively from his august uncle. Youth had served Rupert badly. At the Battle of Edgehill in October 1643, his cavalry completely destroyed the Parliamentary cavalry, but, carried away by the pursuit, Rupert abandoned the field, thus denying the Royalist force the chance to inflict a decisive defeat on the Roundheads.
The prince showed remarkable energy, combining administrative work with military operations throughout 1643-44: he took Bristol, ruled Wales, lifted the siege of York... After the defeat at Marston Moor, Rupert stood at the head of the royalist army, nominally led by the Prince of Wales. Internal disagreements and a number of objective reasons led to defeat at Naseby, after which Rupert doubted the successful outcome of the war for the king and advised Charles to reach an agreement with Parliament.
This was regarded as a malicious intent, of which the king was finally convinced after the prince surrendered Bristol to parliamentary troops. The king dismissed Rupert, who came to Newark and demanded a trial, as a result of which his good name was returned, but not his command. In 1646, Princes Rupert and Moritz were expelled from England by order of Parliament.
On the continent, Rupert led detachments of English emigrants who entered French service and commanded them in military operations against Spain. After the outbreak of the second civil war in England, the prince tried himself as a sailor with varying degrees of success. In 1649, he and Moritz received command of 8 ships and went to Ireland under the command of the Marquis of Ormonde, where he continued the glorious English tradition - he robbed strangers and handed over the loot to his own.
Parliamentary Admiral Blake was sent to put an end to these outrages, and Rupert sailed to Portugal, where he was promised shelter, but Blake caught up with him in the port of Lisbon. Exposed as a pirate, the prince sets off on a free voyage across the Mediterranean and Atlantic. In the spring of 1652, Rupert sailed to the shores of West Africa, where he was wounded in a battle with the aborigines.
He sailed for the West Indies in the summer of 1652, only to find that the royalist enclave of Barbados, where he had hoped to find refuge, had capitulated to the Commonwealth. In the fall, on the way from the Virgin Islands, two of Rupert's four ships were lost in a storm, one of them was commanded by Moritz. Depressed by the death of his brother, the prince returned to Europe in 1653.
Rupert was warmly received at the court of the exiled King Charles II in Paris, but the pleasantries faded in proportion to how the exact amount of booty he brought from the West Indies became clear. The disillusioned prince spent the next six years in obscurity, having quarreled with his older brother over the inheritance.
After the restoration of Charles II in 1660, Rupert returned to England and was well received by the king, despite previous differences. He received an annuity and was appointed to the Privy Council in 1662, his special concern being the state of the navy.
Rupert also took an interest in overseas commercial ventures, becoming the first governor of the Hudson's Bay Company in 1670. The territory granted to the Company was named "Prince Rupert's Land" in his honor. He was also an active shareholder of the African Company. Rupert's contribution to the development of trade was recognized by the foundation stone of the new Royal Exchange.
The Prince, as an admiral, took an active part in the Second and Third Anglo-Dutch Wars, playing a significant role in the Battle of Lowestoft and in the victory of St. James's Day (25 July 1666). From 1673, Rupert devoted himself to administrative work at the Admiralty. He died aged 62 in 1682 and was buried with honors at Westminster.
Continuing his interest in scientific experimentation, Rupert became one of the founders of the Royal Society. In particular, he experimented with the production of gunpowder (the method he proposed made gunpowder 10 times more effective), tried to improve guns, invented an alloy known as “prince metal”, and also developed a device for, so to speak, deep-sea diving
The Prince formulated the mathematical problem of the "Rupert's Cube", achieved famous success as a cipher reader, built a watermill on the Hackney Marshes, developed a naval weapon which he called the Rupertinoe, invented a mechanism to ensure the balance of the quadrant when making measurements on board a ship, tried to improve surgical instruments and was the author extraordinary engravings.
As for his personal life, Rupert never married, but left behind two illegitimate children: son Dudley (1666) from Frances Baird and daughter Rupert (1673) from actress Margaret Hughes (Hughes). The latter, precisely thanks to her connection with Rupert, became the first professional actress in the English theater; in 1669, Margaret, along with male actors, enjoyed the privilege of “royal servants” - she could not be arrested for debts. This was very useful, because she led a wasteful lifestyle.
During their relationship, Rupert gave her jewelry worth 20 thousand pounds, including family jewelry from the Palatinate, and also bought a mansion for Margaret for another 25 thousand. Rupert liked family life - or the semblance of it - he noted with pleasure, watching his little daughter: “She already rules the whole house and sometimes even argues with her mother, which makes us all laugh.” It is believed that Margaret became Rupert's morganatic wife.
He bequeathed his property equally to her and his daughter.
