The flowering of grapes - the third phase of vegetation - begins with the separation of the flower and ...
Let us conditionally single out the outer layer and the inner core in the drop. The droplet is cooled from the surface, and its outer layer shrinks and decreases in volume while the core remains liquid and hot.
After the temperature inside the ball drops, the core will also begin to shrink. But the already hard outer layer will resist the process. With the help of intermolecular forces of attraction, he tenaciously holds the nucleus, which, having cooled down, is forced to occupy a larger volume than if it had cooled freely.
As a result, forces arise at the boundary between the outer layer and the core, pulling the outer layer inward, creating compressive stresses in it, and the inner core outward, creating tensile stresses in it.
These stresses are very high during too rapid cooling. So the inner part of the balloon can break away from the outer part, and then a bubble forms in the droplet.
Very high residual stress results in unusual qualities, such as the ability to withstand a hammer blow on the head of a Prince Rupert drop without breaking its integrity.
But if the tail is slightly damaged, then the drop is destroyed at great speed. The destruction occurs at a speed of 1658 meters per second, which is approximately 5968.8 kilometers per hour.
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.
How Prince Rupert's Drop Was Discovered
Once in Holland, a scientist unknown 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, solidifying in cold water, acquired a bizarre shape resembling tadpoles with a rounded 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 discovery of the scientist was not limited to this, because later he discovered their most curious property.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.
One way or another, the Batavian Tears became widely known after the British Duke Rupert of Palatinate presented them as an outlandish gift to King Charles II of Great Britain. After the king instructed the Royal Scientific Society to investigate their mysterious and funny nature. In honor of the Prince of Palatinate, Batavian tears began to be called nothing more than the glass drops of Prince Rupert. The method of their creation was kept in the strictest secrecy for a long time, but everyone could buy them as a funny souvenir.
Why does Prince Rupert's drop explode?
To date, the reasons for the unusual behavior of glass drops have already been scientifically proven. The fact is that falling into cold water, glass drops quickly harden. Inside each of them a high mechanical stress is formed. If we imagine that the drop consists of a shell and a core, we 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 shrink, but now resistance arises due to the outer frozen layer. Close intermolecular bonds allow it to squeeze the nucleus, which already occupies a larger volume.
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.
Bearing in mind the scientifically proven fact that the outer layer is compressed and the inner layer is stretched, the scientists looked at exactly how pressure is distributed inside the tear. It turned out that the compression force at the outer shell exceeds atmospheric pressure by 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 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.
Modern Application of the Prince Rupert Drop Effect
The principle of Prince Rupert's drop behavior has already been successfully applied in industry. Such glass is familiar to everyone as “tempered”.Previously, “hardened glasses” were produced. They could be dropped on the floor without a twinge of conscience - it never broke on impact. But a chink that accidentally appeared on the edge could provoke its explosion at any time. Therefore, such dishes should be handled even more carefully than with ordinary glass.
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.
Video of the Prince Rupert Drop Effect
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 abrupt 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.
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 ...
What are Prince Rupert drops
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.
How to make Prince Rupert drops
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 the 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:
When and where were Prince Rupert's drops discovered?
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 a drop of Prince Rupert, 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!
