Final answer:
The 1839 invention by Achille Colas for creating scaled copies was related to the process of bronze casting using lost-wax casting, a method where a clay model is turned into a unique bronze statue through a series of detailed steps.
Step-by-step explanation:
The invention of a machine that allowed for scaled copies of sculpture in 1839 by Achille Colas relates to a specific process known as bronze casting through the lost-wax casting method. This ancient process involves sculptors creating a clay model of their intended sculpture, often carried out in several smaller pieces, as described in the historical context provided. The method consists of creating a mold in clay, covering it with wax, and then applying a plaster layer with metallic rods for reinforcement and channels for the wax to flow out when heated. After this setup, intense heat is applied to melt away the wax, creating hollow spaces within the mold that are then filled with molten metal. Once the metal solidifies, the mold is destroyed to reveal the unique bronze statue, which after several finishing steps, such as filling, smoothing, and polishing, is ready for display.