How to Darken Copper

Copper is a natural chemical element. It is related to silver and gold, in part, because it is highly ductile and conductive and virtually unbeaten at conducting heat and electricity. Heavily used in electrical wiring, building components, plumbing, and industrial applications, copper is also used in pharmaceuticals and nutrition. Its natural reddish-brown color is mixed in numerous alloys, such as brass and bronze. This look makes it useful and desired in decorative arts, including furniture, artworks, and jewelry. Copper and its' alloys will discolor over time with varying degrees of oxidation into what is called a "patina" or coating of color. The consumer market for copper and related products wants a variety of patinas and antique finishes, so it is helpful for the designer, creator, and customer to know how to darken copper.

Darken copper naturally

1. Expose copper to environmental elements: air, rain, sun, cold, smog, etc.
   • Copper materials will reach a darkened end-state in time partly depending on their copper content.
   • Patina is the blue-green film that often appears on roofs and other architectural features; it is very difficult to duplicate artificially.

Darken copper with liver of sulfur

1. Clean the item with a clean lint-free rag dampened with clear, grease-cutting household cleaner.
2. Apply liver of sulfur to create oxidation on copper surfaces.
   • Liver of sulfur is sulfurated potash which is a mixture of potassium sulfide, potassium polysulfide, potassium thiosulfate, and potassium bisulfide.
   • Liver of sulfur is easily available online and can be purchased in dry lump and gel forms.
   • Liver of sulfur turns copper black quickly and deeply, so experiment with applications that have been thinned with distilled water to secure the finish you prefer.
3. Wipe item clean and dry with a clean lint-free rag.

Darken copper with green patina

1. Wipe item clean with a clean lint-free rag dampened with clear, grease-cutting household cleaner.
2. Mix darkening solution of 2 parts white vinegar, 0.50 part non-iodized salt, and 1.5 parts of clear, detergent-free ammonia.
3. Spray item with darkening solution.
4. Allow to set for 1 hour.
5. Reapply solution with special attention to areas missed on first try.
6. Allow patina to dry to green powdery finish.
   • Do not rub powder finish off; patina will set permanently in time.
7. Allow to sit overnight.

Darken copper with brown patina

1. Clean item with a clean lint-free rag dampened with clear, grease-cutting household cleaner.
2. Add baking soda to hot water until it will no longer dissolve, and fill spray bottle with this darkening solution.
3. Spray item with darkening solution.
   • Use cotton swabs dampened with the solution to wet hard-to-reach places.
4. Allow to sit for an hour, and reapply to achieve the brown, copper penny finish you want.
   • Brown darkening solution will not powder like green solution.

• Lump form liver of sulfur has a very short shelf life.
• Copper will not respond to magnets, so if a magnet attaches to your copper, it is likely copper-plated and may not respond well to these darkening treatments.
• If using green patina solution, reduce salt content to reduce intensity of green.
• A dry environment will hamper patina; humid climates and environments promote patina.

• Wear safety equipment, including work gloves, goggles, and masks, and minimize skin exposure to avoid negative effects these products can cause.
• Metal darkening solutions can be dangerous to eyes, skin, and respiratory system; have first aid and emergency measures in place.
• Metal darkening solutions, waste, and clean-up rags are hazardous wastes and must be disposed up according to regulation.
• Lump form liver of sulfur is flammable and an inhalation hazard.

• Liver of sulfur
• Hot water
• Baking soda
• White vinegar
• Non-detergent ammonia
• Non-iodized salt
• Clean soft lint-free rags
• Spray bottles
• Distilled water
• Clear, detergent-free ammonia