Colour, shine, texture and smell are properties that were much appreciated by ancient societies, and they played an important role in their technologies.

To control them, goldsmiths developed various metallurgical innovations and techniques, such as creating a selection of alloys with a wide range of colours, or sophisticated finish processes which brought new tones and contrasts to surfaces.

When a tumbaga object is heated, the copper that is present in the alloy oxidises and forms a dark stain on the surface. The craftsman removed the oxidised copper with vegetable acids until a thin surface layer rich in gold was left, which he then polished in order to achieve an intense gilding.

Sheep sorrel, Oxalis pubescens, was used to obtain oxalic acid for removing oxides from the surfaces of objects oxidised by fire. With use or with the passing of time, the surface gilding of these objects has deteriorated, revealing the tumbaga that is inside them.

In objects like Nariño spinning disks, contrasting colours were obtained by scraping the thin surface layer of gilding in certain areas, to reveal the reddish colour of the alloy. When the surface of an object was attacked with a salt or acid paste, it became porous and turned a matt colour. Other parts, which were protected beforehand with resins, remained shiny.

Ornaments that reflect light were carefully polished and burnished by the metalsmith with stone polishers; other objects were left unpolished and trap the light. The goldsmiths of the Eastern Cordillera, for instance, did not polish objects that were to be given up as offerings.

Gold artefacts were greatly valued by pre-Hispanic societies, because of both the meanings and stories attached to them and the materials, knowledge and skill involved in working them. Many of these objects were therefore repaired by goldsmiths.

Some got damaged through constant use and were remade using wires, bands or rivets, while others, which had manufacturing defects, were repaired using new metal pourings or, as in the case of the filigree earrings from the Caribbean Plains, by mending the weave with metal threads.

Time and nature do their best to reclaim the materials used by the goldsmith. Most metals and their alloys, apart from gold, tend to suffer major transformations when they are being used, and also afterwards when they are buried.

The copper that is present in pre-Hispanic alloys reacts with the moisture and salts in the ground and produces oxides, in a process known as corrosion. Conservation and restoration in the Museum set out to halt this deterioration, so that our heritage can be preserved.
The warp and weft of the blanket that covered a deceased person on the high plains of Nariño were left imprinted in the layer of oxides on the back of this breastplate. The marks left by the person's seed necklace can be seen on the front.