Creating contrast between smooth and rough metal surfaces is a powerful design technique that enhances visual interest and tactile appeal. Here are the most effective methods to achieve this striking effect:

1. Mechanical Finishing: Use grinding or polishing for smooth areas while leaving other sections untreated or sandblasted for roughness. This method highlights the duality of textures.

2. Chemical Etching: Apply acid or chemical treatments to selectively roughen specific areas, creating a deliberate contrast with polished sections.

3. Laser Engraving: Precision laser techniques can produce intricate rough textures alongside smooth surfaces, ideal for decorative metalwork.

4. Anodizing or Coating: Combine glossy anodized finishes with matte or brushed sections to amplify the contrast in both texture and reflectivity.

5. Mixed Media: Incorporate other materials like wood or stone alongside metal to emphasize its smooth or rough qualities through juxtaposition.

By strategically combining these techniques, designers can create dynamic metal surfaces that engage both the eye and the touch, elevating the overall aesthetic impact.