The surface of rotating discs and other items produced in the Nariño area feature geometric designs made of gilded, polished areas alternating with zones that have been scraped or dulled through the application of salts and acids, or blackened zones formed through the oxidation of porous surfaces. 
  
Symbolically, the contrast between bright, reflective areas and opaque, darker ones is likely associated with the contrast between male and female energies, life and death. Functionally, disks like this were suspended by a string through the hole in the center and spun. The contrasting colors produce a dazzling visual effect, possibly used for inducing visions or producing a particular state of mind.

Video Transcript

Depletion Gilding

The ancient metalsmiths worked with different tumbagas, which were alloys of silver-bearing gold and copper. 

With just as little as 5% gold content and 95% copper they managed to produce objects with gilded surfaces. 

Fire oxidizes copper; the oxides migrate to the surface and cover it. 

The metalsmiths ground an herb to obtain an acid, which they mixed with boiling water and salt. 

When the object was submerged in this hot solution, the action of the acid removed the copper oxides.

The object was then cleaned and polished with water and abrasive materials. 

The final thickness of the gilding depended on how many times the process was repeated.