Top pic:
Late Spring and Autumn / Early Warring States Period bronze sword (around 500 BC), utilizing laminated construction -- using bronze alloy with higher tin content for the cutting edges and bronze alloy with lower tin content for the median ridge or spine.
Increasing the percentage of tin in the bronze alloy (bronze is made from copper alloyed with tin) actually increases the physical hardness of the bronze alloy, while lowering the tin content actually makes the bronze alloy softer and less hard.
In general, these swords would have edges and spines cast from bronze alloys with tin contents of 20% and 10% respectively.
The intended purpose was to create harder cutting edges for enhanced thrusting/slashing performance plus a softer and more flexible spine to absorb shock and prevent breakage.
The actual manufacture involves first the creation of a stone or pottery mould with the hollowed section in the shape of the spine of the sword. Molten bronze with 10% tin content is then poured in and allowed to cool. Afterwhich the newly cast end-product, the spine of the sword, is removed from the mould and placed within another specially-created mould with hollowed sections along both sides of the spine. Molten bronze with 20% tin content is then poured in to make up the cutting edges of the sword and allowed to cool. The molten bronze cools and fuses with the preliminary spine of the sword and the whole manufacturing process is completed.
This bronze laminated construction we encounter here was the ancestral prototype of the forge-welded/laminated construction seen later in the steel swords of the Han and Tang Dynasties.
For other bronze and steel swords of this period, go to: http://chineseswords2.freewebspace.com/custom2.html
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Bottom pic:
Qin Dynasty bronze swords (221-206 BC). Distal-tapered and coated with a corrosion resistant protective layer consisting of a chromium compound, these swords can be used with a 2-handed grip.
This type of bronze sword was also manufactured during the early part of the Han Dynasty. One of them, from the Han era, was reported to have been exceptionally long -- with a overall total length of 111 centimeters and a 2-handed grip length of 23 centimeters.
