The correct option is 1, 2, 3 and 4.
Explanation
The Harappans practiced the art of bronze casting extensively using the 'lost wax' technique, technically known as Cire Perdue. This method was essential for creating intricate metal sculptures, such as the famous 'Dancing Girl' found at Mohenjodaro.
Statement-wise Analysis:
- Statement 1 is Correct: The process commenced with the creation of a wax model of the desired figure. This wax model was subsequently covered with a thick coating of clay and allowed to dry to form a rigid outer mould.
- Statement 2 is Correct: Once the clay coating dried, the assembly was heated. The heat caused the wax inside to melt, which was then drained out through a tiny hole made in the clay cover, leaving a hollow cavity.
- Statement 3 is Correct: The hollow clay mould was then filled with molten metal (typically bronze or copper) poured through the same aperture.
- Statement 4 is Correct: The metal was allowed to cool and solidify within the mould. The clay cover was removed (broken off) only after the metal had completely cooled, revealing the final cast figure.
Key Takeaway:
The Cire Perdue or 'lost wax' technique involves a four-step process: wax modeling, clay encasing, de-waxing via heat, and metal casting, which was the standard metallurgical practice for art in the Indus Valley Civilization.