President
"Our ancestors created an excellent tradition also in the fields of science, culture and the arts, which can surprise the world."
The Koryo people not only made a name for making Koryo ceramic that was unique in color, pattern and design, but also developed superb metal processing art whose excellence was no less than ceramic processing technology.
The white copper and the black copper that were made in Koryo dynasty were the materials made from bronze and were used to enhance the beauty of the craft piece by making its ground color white or black. No wonder they represent valuable cultural heritage that reveal rich and creative wisdom and outstanding skills of Koryo people.
Since the primitive times spanning ancient Joson and Koguryo dynasty our ancestors have dynamically developed copper alloy technology and finally have come up with bronze materials of different beautiful colors in Koryo dynasty.
The white copper of Koryo dynasty, a type of tin bronze with beautiful white color, was widely used in making various kinds of ornaments.
Generally copper makes good alloy with such metals as gold, silver, tin, lead and zinc and its color and physical nature vary according to which element it is alloyed with. The white colored copper alloy, i.e. white copper, well known in modern industry is a type of copper alloy that contains 10~30% of nickel in it and its color turns from reddish to silver white when nickel content increases.
In the same way when copper makes alloy with tin, we get various-colored tin bronze alloy and if the content of tin is increased to 25-32% the color of the alloy turns into silver white. The white copper alloy and white copper mirror cast by Koryo people contained more than 25% of tin and 0.005% of nickel, which means that the white copper of Koryo dynasty was tin-copper alloy, not nickel-copper one.
The white copper of Koryo dynasty had similar color, resistance to rust and mechanical nature to those of today's copper-nickel alloy. The people of Koryo dynasty who attained rich experience and technology in their long history of developing bronze materials, found out that one could get different colors of bronze materials with varying degrees of tin content and managed to get silver white copper by simply changing the content of tin in the copper alloy.
This is a good manifestation of wisdom and talent of Koryo people who successfully made the white copper similar to that of modern times by making copper alloy not of nickel, but of tin.
Black copper, reddish black tin bronze alloy was used to create various metal craftsmanship.
The surface color of copper-tin alloy changes also when it is oxidized at different temperature. When the alloy is heated in 650~750℃, in particular, it turns into reddish black with more smooth surface. And this is how the black copper of Koryo dynasty come into being.
Indeed, the white and black copper are the products of creative wisdom of intelligent and skillful Koryo people and together with Koryo ceramics the craftsmanship made from white and black copper testify to the high level of development of science and culture of our country.
