Now, let us see how they made the bell. To do so, we need to know the basic characteristics of bronze. Bronze is an alloy of tin and copper. And bronze melts at a lower temperature than copper. But tin actually makes copper harder. So, bronze is harder than copper. And the most important characteristic of bronze is that it's much less brittle than cast iron. So, ancient people chose to make a bell with bronze, not with iron, because iron bells are too brittle. They break easily. And another important factor is that bronze is highly resistant to corrosion as you can see in this picture. So, the right picture shows various swords made in the 50th century. Those are iron swords. And the are mostly actually corroded with rust. But the left bronze swords are still in good shape as you can see. But they were actually made much earlier. They were made around the 2nd or the 3rd century BCE. So, bronze is much more resistant to corrosion. And that's the reason, that's one of the reasons why this bell is still in its original shape, making beautiful sound. And there is this secret about what was the combination of tin and cooper. So, the higher the percentage of tin, the clearer the sound of the bell becomes. But the problem is that more tin makes the bell brittle. It makes the bell break easily. So they tried. We expect, we believe that actually they tried various methods to find the right combination. And the secret was this. So, they used 18% of tin and 82% of copper. This composition is a little bit different from the composition of most bronze bells made in the West, in Europe, and in China actually. In Europe, people made bells with bronze with 23% of tin. But ancient Silla people used bronze with 18% of tin, making the bell more long-lasting. And this is how they made the bell. So, this process is basically the same as the one we currently use. First, they make this basic structure, like this, with clay and straw and various other things. And they put beeswax and lard on the surface of this basic structure to make an exact model of the bell. So, this is the exact model of the bell. And then, they put this model onto this hole. And they put clay on the surface of this beeswax to make a mold, and then applied heat to melt the wax away. So, they removed the wax so that the mold have hollow space in it with the exact negative image of the bell. And they poured molten bronze onto the mold to make the bell. This sounds easy, you know, when you make... This is relatively easy when you try to make a small object. But this is a bell weighing 19 tons. It was extremely... It was really extremely difficult to control every element of this whole process. And somehow... As we remember, if you remember, it took 30 years to make this bell. And in the 90s, two exact copies of this bell were made. And one of the copies is currently in Los Angeles in the U.S. It is named the Korean Bell of Friendship. It looks like... The Korean Bell of Friendship looks like the Sacred Bell of King Seongdeok. Very very alike. But it does not make as good sound as the Sacred Bell does. Another copy is in Bosingak in Seoul. But it does not make as good sound either. So, the secret of making this bell making this beautiful... beautiful-sound-making bell is still unknown.
