Usually when engraving metals, the best results can be achieved using a pre-coated metal that has been surface treated; anodised, lacquered, powder coated, or spray veneered. The laser will then remove this surface to reveal the metallic surface below.
To mark a bare metal surface, we must run the laser very slowly at a high power. When doing this, the laser is not actually removing any of the material, it is altering the surface structure of the metal. This results in different colour variations ranging from gold to purple (depending on the metal used). Different powers / speeds produce different results.
We do not advise using this process if you are after a very slick clean finish, but it is great for more artistic applications.
Using a variation of powers and speeds we can build up a rich depth of subtle colour variation.
Another method of marking bare metals is Compound engraving.