24 August 2024
Eben van Tonder

In ancient sword-making, pattern welding was a sophisticated technique that involved combining layers of steel with different carbon contents, forged together to create a stronger and more flexible sword. As H. Foll describes it, “Pattern welding is a special way of constructing a sword blade from a lot of iron/steel parts. Many different kinds of iron/steel parts are fire-welded in such a way that a pleasing pattern can be observed on one or both sides of a blade. The pattern results because two sufficiently different kinds of iron/steel that intersect the surface reflect the light differently, in particular after some special polishing or etching. You thus must use very special shapes of the parts to be welded to produce a specific pattern, and you must use quite different kinds of iron and steel to render the pattern visible. In other words: You must do structural and compositional piling, and you must do it in a way that produces the pattern you are after” (Foll, 2024). This intricate method not only enhanced the blade’s structural properties but also imparted a unique aesthetic quality, making the weapon a symbol of both craftsmanship and combat effectiveness.

Carburizing with Animal Droppings: Ancient Techniques for Creating Steel

One of the lesser-known yet remarkable methods used by ancient blacksmiths to enhance the quality of steel involved the process of carburizing using animal droppings. Carburizing is the process of introducing carbon into iron to form steel. In antiquity, materials rich in carbon, such as animal dung, were utilized to infuse iron with the necessary carbon content. The process involved packing iron in a mixture of charcoal and dung and then heating it in a forge.

The Process of Carburizing:

1. Preparation: The iron was surrounded by carbon-rich materials, including animal droppings and charcoal, which acted as the carbon source.
2. Heating: The packed iron was heated to a high temperature, typically around 900–950°C. This heat allowed the carbon from the droppings and charcoal to penetrate the surface of the iron, forming a layer of high-carbon steel. This process typically required several hours, with the depth of carbon penetration depending on the duration of heating.
3. Result: The resultant steel was harder and more brittle due to the increased carbon content, which was ideal for creating sharp edges on tools and weapons.

The use of animal droppings in this process shows the resourcefulness of ancient blacksmiths and the advanced understanding they had of material properties. The application of dung and urine in carburizing is further discussed in historical texts and records, such as those reviewed by Earthworm Express, where it is noted that these organic materials were essential in the early development of steel-making techniques (Earthworm Express, 2024).

Control of Hardness and Flexibility in Steel

Ancient swordsmiths needed to balance the hardness and flexibility of steel to create a weapon that could withstand the rigours of combat. High-carbon steel was used for the blade’s cutting edge, providing the necessary hardness to retain a sharp edge, while low-carbon steel was used for the core or back of the blade to impart flexibility and shock absorption.

• High-Carbon Steel (Hard and Brittle): Sections of the blade requiring a sharp edge, such as the cutting surface, were made from high-carbon steel. This steel held an edge well but was more brittle and prone to breaking if subjected to excessive force.
• Low-Carbon Steel (Soft and Pliable): Low-carbon steel, which had less exposure to the carburizing process, was used for the core or back of the sword. This steel was softer and more flexible, allowing the blade to absorb shocks without breaking.

The balance between these two types of steel was achieved by carefully controlling the exposure of iron to carbon sources (such as dung) and by adjusting the time and temperature of the carburizing process.

Pattern Welding: Combining Different Steels

Pattern welding is the technique of forging together multiple layers of steel or iron, typically with varying carbon content, to create a single blade with both strength and flexibility. This process results in the distinctive, often intricate patterns on the surface of the blade, which are both visually striking and functionally beneficial.

Step-by-Step Process:

1. Layering: After the carburizing process, the blacksmith would take alternating layers of high-carbon and low-carbon steel.
2. Forging: These layers were heated and hammer-forged together. The heat and pressure effectively welded the layers into a single block.
3. Folding: The block was then folded over and hammered again, creating more layers and increasing the strength of the steel. This folding process could be repeated multiple times, depending on the desired strength and pattern.
4. Pattern Creation: To create the desired patterns, the smith might twist or manipulate the layers before forging them flat again. The manipulation of the layers, combined with the different carbon contents, resulted in the beautiful, wavy patterns characteristic of pattern-welded blades.
5. Quenching: The blade was finally quenched, typically in water, oil, or even urine, a practice noted in historical texts, which rapidly cooled the steel, hardening it and locking in the properties created by the forging process. The harder outer layers remained sharp, while the softer core provided flexibility.

Purpose and Benefits of Pattern Welding

Pattern welding served multiple purposes in sword making:

• Strength and Flexibility: By layering different types of metal, pattern welding allowed smiths to create a sword that combined the hardness required for a sharp edge with the flexibility needed to prevent the blade from shattering during use.
• Aesthetic Appeal: The unique wavy patterns resulting from the process added a level of beauty to the sword, making it not only a functional weapon but also a symbol of the blacksmith’s skill and artistry.
• Combat Effectiveness: The combination of softer, flexible layers with harder, brittle layers provided a balance between a sharp cutting edge and a blade that could absorb impacts without breaking.

Conclusion: The Ingenuity of Ancient Blacksmiths

The use of animal droppings in the carburizing process, combined with the advanced technique of pattern welding, highlights the ingenuity of ancient blacksmiths in overcoming the limitations of available materials to produce high-quality, durable weapons. By controlling the carbon content of the steel through carburizing, and then skillfully combining different layers of steel through pattern welding, these craftsmen were able to create swords that were not only effective in combat but also aesthetically beautiful, with their distinctive patterned surfaces.

This process, detailed by H. Foll and supported by historical references, underscores the sophistication of ancient metallurgy and its enduring legacy in the art of sword-making (Foll, 2024; Earthworm Express, 2024).

References

• Foll, H. (2024). Pattern Welding: A Special Way of Constructing a Sword Blade. Retrieved from H. Foll’s Material Science
• Earthworm Express. (2024). A Reevaluation of the Discovery of Nitrate and Nitrite Curing. Retrieved from Earthworm Express
• All Images from Foll, H. (2024). Pattern Welding: A Special Way of Constructing a Sword Blade. Retrieved from H. Foll’s Material Science