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Prince Rupert's Drops (also known as Dutch tears) are glass objects created by dripping molten glass into cold water. The glass cools into a tadpole-shaped droplet with a long, thin tail. The water rapidly cools the molten glass on the outside of the drop, while the inner portion of the drop remains significantly hotter. When the glass on the inside eventually cools, it contracts inside the already-solid outer part. This contraction sets up very large compressive stresses on the surface, while the core of the drop is in a state of tensile stress. It is a kind of toughened glass. The very high residual stress within the drop gives rise to counter-intuitive properties, such as the ability to withstand a blow from a hammer on the bulbous end without breaking but explosive disintegration if the tail end is even slightly damaged. == Description == While the head of the drop can be hit with a hammer without breaking, when any portion of the tail is damaged, the large amount of potential energy stored in the internal structure is released, causing fractures to propagate through the glass toward the head at very high speeds which break the entire structure into flakes and powder. An examination of the shattering of Prince Rupert's Drops by the use of high speed video〔(【引用サイトリンク】title=Mystery of Prince Rupert's Drop at 130,000 fps )〕 has revealed that the "crack front" which is initiated at the tail end propagates in a disintegrating drop within the tensile zone towards the drop's head at a very high speed (). Because of the transparency of glass, the internal stress within these objects can be demonstrated by viewing them through polarizing filters, a technique used in the study of photoelasticity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Prince Rupert's Drop」の詳細全文を読む スポンサード リンク
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