Copper is a light-colored iron that is often used for decorative purposes, including furniture, art work, and jewelry. Over time, the copper surface will react with oxygen, heat, and other environmental aspects to cause a layer of color, or patine. While the patina is usually green, it may also turn a dark brown or even black patina on your copper. Each treatment produces a slightly different color, so you can try a few on your copper items to see which result you like best.
Step
Method 1 of 3: Darkening Copper with Boiled Eggs
Step 1. Use this method for easy and relatively minor adjustments
Egg yolks from hard-boiled eggplant can produce sulfur and other chemicals that react with copper to change the color to a darker brown or black. While this method will take longer and won't produce as dramatic results as using liver of sulfur, you won't need anything other than a hard-boiled egg and a sealed container.
Step 2. Boil two or more eggs until cooked
Use two or three eggs for copper jewelry or more if your item is larger or more than one. Place the eggs in a pot of boiling water and let sit for at least 10 minutes. The smell of overcooked sulfur and the greenish ring around the yolk are good indications that the eggs are darkening your copper.
Step 3. Break the egg into several pieces
Use a spoon or other tool to crush the egg into pieces. If the container you're using is a bag, it may be best to put the eggs in first.
Step 4.. Put the copper and egg in the container
Try not to touch the egg to the copper to avoid colored dots on your copper. Better yet, place the copper on a small plate or on the other side of the container.
Step 5. Seal the container
Install the cover or seal the plastic bag. The container must be airtight so that the gases produced by the eggs are concentrated enough to affect the copper.
Step 6. Check regularly
Depending on the freshness of the eggs and the quantity of eggs used, you may start to see results within 20 minutes or a few hours. Check every half hour or so, or if you want the copper to be darker, leave it overnight.
Step 7. Scrub excess stain if necessary
Use a clean rag to rub off excess color if the copper gets too dark, or if you want to create more variables, reducing the even effect.
Method 2 of 3: Darkening Copper with Liver of Sulfur
Step 1. Follow these instructions for significant changes
Liver of sulfur, made of potassium sulfide and other chemicals, reacts with copper to create different colors. Although this material is more expensive and potentially more dangerous than the ingredients used in other methods, it is the best opportunity to create a darker patina.
Step 2. Clean the copper
Wash the copper thoroughly with warm soapy water. Copper that is clean enough, without the luster of oil or dirt attached, can be scrubbed using a clean cloth or household cleaner.
Step 3. Get liver of sulfur in liquid, gel or dry form
Liver of sulfur can be purchased in several forms. Liver of liquid sulfur has been dissolved, but can only be stored for a few weeks. The gel and dry forms must be mixed with water before use, but if stored properly they last longer. Be aware that the dry form, sold as liver of sulfur "blobs" or "nuggets", can emit dust that can be harmful if inhaled.
Step 4. Work with gloves in a ventilated area
Wear latex or rubber gloves before handling liver of sulfur, as they can irritate the skin. Work outside or in a well-ventilated area, especially if you use dry liver of sulfur. Liver of sulfur has an unpleasant pungent odor, which ventilation will reduce. If you have eye protection, wear it.
- If liver of sulfur comes into contact with skin, remove clothing to expose the affected area and rinse under running water for 15 minutes.
- If this material gets into your eyes, rinse under running water for 15 minutes, occasionally moving your lower and upper eyelids to expose your eyes to the water. Seek medical attention.
- If you ingest liver of sulfur, force yourself to vomit it and seek medical attention.
Step 5. Dissolve the liver of sulfur
The dried liver of sulfur should be tapped gently until you break the pea-sized nuggets; an ingredient darker than the inside of the clot will be more effective. Mix these pea-sized nuggets with about 1 cup (240 ml) of water. The gel or liquid should be dissolved according to the instructions, as different brands contain different liver of sulfur concentrates or may have been dissolved at the correct strength.
Cold water and more soluble liquids should work when treating copper, and you'll have better control over the color. Using warm or hot water may darken your copper faster, but never mix liver of sulfur with boiling water, as this produces harmful gases
Step 6. Prepare the baking soda bath in advance
The baking soda will neutralize the liver of sulfur, preventing it from darkening your copper more than you'd like. Prepare a mixture of baking soda and water ahead of time so you can stop the discoloration as quickly as you'd like. In a separate bowl from the liver of sulfur, mix in about a ratio of one baking soda to sixteen water. Use a container large enough to soak your copper object in.
Step 7. Use tongs to dip the copper into the liver of sulfur for a second or two
Using tongs and gloves, or tweezers for smaller objects, briefly hold the copper under the surface of the liver of sulfur.
If your copper is too large to dip into the solution, use a brush to apply the solution, or transfer the solution to a wider, shallower container
Step 8. Repeat until you reach the desired color
Remove the copper from the solution and observe the color change, being careful not to hold it near or over the unprotected eye. Depending on the concentration of the solution, and the temperature of your copper, you may see any color from pink to black. Dipping it in the solution several times should produce a darker color, ending in a gray or black patina.
- If the discoloration is minor, try heating the copper in a pot of hot, but not boiling, water. Higher temperatures should produce more dramatic color changes.
- If the color isn't dark enough, try mixing 1 teaspoon (5 milliliters) of pure ammonia into the solution. Adding ammonia may produce a reddish color instead of black.
Step 9. Clean the copper with baking soda to stop the discoloration
Once you've reached your desired color, let your copper soak in the baking soda bath for a few minutes. Remove and wash using warm soapy water.
- If the discoloration is too far off, or if you want a more uneven and vintage appearance, rub the patina gently with iron wool or a paste made of baking soda and a few drops of water.
- Baking soda can also be added to the liver of sulfur solution after you're done. This will neutralize the liver of sulfur and allow you to safely flush it down the sink.
Step 10. Treat your copper with wax or varnish to maintain its color
Any wax or varnish made for iron can be applied over the new patina depending on the product's instructions. This will prevent or slow further discoloration as long as the wax or varnish is kept clean and not rubbed off.
Method 3 of 3: Dyeing Copper Green or Brown with Self-Mixed Solutions
Step 1. Mix your own solution to get a specific color
The natural green copper patina can be imitated using an ammonia solution, whereas the darker colors on American coins can be made with baking soda and water. Because the applications of these solutions are so similar, they are described in this section.
Step 2. Clean your copper
Scrub clean with a dry cloth. Dirty copper can be washed with warm soapy water, then dried thoroughly.
Step 3. Follow safety procedures when working with ammonia
If you are trying to make a green patina, you will need to use ammonia. Work outside or in areas with strong ventilation systems or fans. Ammonia vapors can be toxic, so ammonia should never be used in confined spaces. Rubber gloves and eye protection are recommended.
To make a chocolate patina using baking soda and water, no safety precautions are required
Step 4. Use ammonia for a green patina solution
Stir in 2 cups (or 500 ml) white vinegar, 0.5 cups (or 125 ml) non-iodized salt, and 1.5 cups (or 375 ml) clear ammonia. Ammonia can be found in some grocery and drug stores, but don't buy the weaker "detergent" types.
The more salt you add, the greener the patina will be
Step 5. Mix the brown patina solution
This solution will turn your copper into a dark brown, like the color of American coins. Simply stir the baking soda in a bottle of hot water spoonful at a time, until the additional baking soda doesn't dissolve.
Step 6. Spray the copper with this solution
Use a spray bottle to apply the patina to the copper surface. Spray more if you want a more even finish instead of smudging or patterning.
Step 7. Store in a damp area for 1-8 hours
This patina may take up to several hours to develop, but keeping it in moist air will speed up this process. If the copper is placed in a dry area, use a plastic bag or plastic sheet to cover the copper without touching the surface.
Step 8. Reapply the solution if the patina fades
Depending on the environment in which the copper is stored, and how often it is handled, the patina may fade or fade before settling permanently. If this happens, reapply as before, on all surfaces and areas where the patina has faded.
Green patina are usually more powdery and easy to rub than brown ones
Tips
- If using a green patina solution, reduce the salt to reduce the intensity of the green color.
- Prolonged exposure to a humid environment will cause your copper to oxidize slowly, resulting in a green patina. Consider leaving your copper outside to speed up this process.
- Copper will not respond to magnetism. If the magnet sticks to your copper, it's likely copper-coated or made of a different material, which may not respond well to darkening.
- Liver of sulfur should be stored in an airtight container in a dark, dry location.
- If you have access to a box or chemistry lab, consider trying this formula for different patina colors. Be aware that these were collected from many sources without careful experimentation, and should be applied to the invisible ends first.
Warning
- Iron darkening solutions can be harmful to the eyes, skin, and respiratory system; have first aid and emergency kits available.
- Liver of sulfur in lumps is flammable and dangerous if swallowed.
- Wear safety equipment, including work gloves, eye protection, and a mask, and minimize skin exposure to prevent the negative effects this product can have.
- Iron-dark solutions, dirt and cleaning cloths are hazardous waste and must be disposed of in accordance with regulations.
