Achieving a smooth, even patina on metals like copper, brass, or bronze requires careful technique and attention to detail. Streaking or uneven coloration often occurs due to inconsistent application or environmental factors. Here are the best methods to prevent these issues:

1. Surface Preparation: Clean the metal thoroughly with a degreaser or mild abrasive to remove oils and residues. A pristine surface ensures uniform patina adhesion.

2. Controlled Application: Use a spray bottle, brush, or sponge to apply patina solutions evenly. Avoid pooling or excessive liquid, which can cause streaks.

3. Environmental Control: Work in a stable environment with consistent temperature and humidity. Sudden changes can disrupt patina formation.

4. Layering Techniques: Apply thin, multiple layers rather than one heavy coat. Allow each layer to dry completely before adding the next.

5. Neutralizing Residues: After achieving the desired patina, rinse the metal with distilled water or a neutralizing solution to halt further chemical reactions.

6. Sealing the Patina: Protect the finish with a clear wax or lacquer to prevent oxidation inconsistencies over time.

By following these steps, you can minimize streaking and achieve a professional, even patina. Experiment with different techniques to find what works best for your project.