From 1889 until 2019, the kilogram was defined as the mass of a physical object. The International Prototype of the Kilogram, a platinum alloy cylinder measuring 3.917 centimeters in height and diameter, remained the sole metric unit linked to a tangible artifact. However, due to inevitable changes in the physical properties of an object, using the International Prototype and its replicas stored in various countries to standardize and regulate weight measurements proved unreliable. In his ongoing series, Andrés Ramírez Gaviria presents an image of the International Prototype of the Kilogram, as well as some official copies.
