STORY 7: "People in ancient times are great!"

Sure! Think about this. A "low melting temperature" simplifies soldering work. For soldering work, we must heat up the target metal to the solder's melting temperature or higher temperature, as well as heat up the solder. For this purpose, the soldering tool must be heated up to a higher temperature. If the solder's melting temperature is high, it is difficult to heat up the target metal and the soldering tool. Furthermore, if the target metal is excessively heated up, the metal may be damaged.

I see. Also, which types of soldering irons were used in that time without electricity?

They used metallic irons heated with coal and so on.

Oh, really? People in ancient times were really intelligent. When was soldering used first in Japan?

It is not exactly known but it is said that soldering was used before the eighth century. I hear that soldering was used for Shoso-in and the Great Buddha at Nara. In that time, various handicrafts related to building of the Great Buddha had been created and soldering was used for these handicrafts. In addition, a description of soldering was found in a document created in the Edo era. Do you know about book called "Wakan-sansaizue"?

What is it? Is it an illustrated book for children or something like that?

No! This book, named "Wakan-sansaizue", is an encyclopedia from the Edo era. It is a great book that "Ryoan Terashima", a doctor in Osaka, spent thirty years or longer to edit. All the text was written in classical Chinese, but this book contains many illustrations so we can enjoy it just by browsing through them. Look at this! Ha-ha-ha (Laughing)

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This book says that "lead of one kin is mixed and kneaded with Chinese tin of ten ryo, and the mixture is used?."; "one kin" corresponds to about 600 g and "ten ryo" corresponds to about 375 g. So, this is the description of soldering that uses lead and tin at a ratio of 6 to 4.

Why was such an old technology subjected to little change until now? Other technologies have rapidly changed, haven't they?

That is because ·····. Oops, it's time for me to go out now! Sorry, I'll answer your question another time. You have to go now.

Huh?!