If you want to give a rustic or antique touch to your copper jewelry and objects, you can cover them with a patina by oxidizing them. You can do this without having to buy expensive kits at craft stores; The methods described in this article allow you to coat the copper with a brown, green, or blue-green patina. Each technique produces slightly different results, so you can experiment to find the one that best suits your needs. If you want to maintain good control of the result, use the liquid solution method.
Steps
Method 1 of 3: Aging the Copper with Hard Boiled Eggs (Light Brown or Dark Brown Patina)
Step 1. Boil two or more eggs
Unless you need to age a large amount of copper, two or three eggs should be enough. Put them, with their shells, in a pot of water and bring them to a boil for at least 10 minutes. Don't worry if you overcook them, in fact what you need is the smell of sulfur and the green ring that forms in overcooked eggs. Sulfur is the element that alters the color of copper.
Step 2. Use kitchen tongs to place the eggs in a plastic bag
Choose a bag that can be sealed and be sure to use tongs or another similar tool to avoid burns. If you don't have a bag large enough for the eggs and the copper item, then get a tapperware container, bucket, or jar that has a lid. The larger the container, the greater the number of eggs needed.
In theory, the container should be transparent in order to control the oxidation process without having to open it
Step 3. Crush the eggs into small pieces
Close the bag halfway to avoid splashing the egg pieces all over the place. From the outside of the bag, poke the eggs with a spoon, cup, or other heavy object. Break the shell, egg white and yolk into small pieces.
Do not seal the container completely, otherwise an air pocket will remain and prevent you from working carefully
Step 4. Place the copper object on a small plate
This prevents it from coming into direct contact with the eggs, which will save you from having to wash it and no darker spots will form in the contact areas.
Step 5. Put the plate with the copper object inside the bag and seal the bag
It is not important that it is near the egg pieces, the key thing is that you do not touch them directly. Close the bag to trap the sulfur fumes or put the lid on the container. The bag will increase in volume due to the heat given off by the eggs but should not break.
Step 6. Check the contents regularly to assess the color of the copper
Sometimes it takes 15 minutes to see the first results but more commonly it takes 4-8 hours to achieve a nice dark brown shade. The copper should become darker as it remains in the bag and the surface acquires an aged and uneven appearance. Remove the item from the container when you are satisfied with the result.
Wash the copper to remove any pieces of egg that are stuck and to evaluate their appearance once cleaned
Method 2 of 3: Oxidize Copper with a Liquid Solution (Green, Brown and Other Colors)
Step 1. Scrub the copper with a scouring pad and water
Make linear movements to give the metal a certain grain, so the patina develops without blemishes. You can skip this step or just try on some areas if you want to create an art object that juxtaposes new copper sections and aged sections.
Step 2. Clean the metal with mild dish soap and rinse it thoroughly
Eliminates foam, greasy residue and patina. Dry it with a clean cloth.
Step 3. Prepare a solution based on the color you want to achieve
There are many possible mixtures that you can use to oxidize copper and they vary according to the desired end result. Below you will find a list of liquids that require the use of normal products present at home or that can be purchased at the supermarket.
- Warning: Always wear rubber gloves and work in a well-ventilated room when using ammonia. Protective goggles and a respirator are also recommended. Carefully wash your skin or eyes with running water for at least 15 minutes in case of accidental contact.
- To get a green patina, mix 480ml of white vinegar with 360ml of pure ammonia and 120ml of salt. Mix everything in a spray bottle until the salt has dissolved. If you want a “less” green patina, reduce the amount of salt.
- To get a brown patina, mix baking soda in a spray bottle filled with hot water. Keep adding it until it no longer melts.
- You can also try purchasing copper antiquing solutions and following the instructions on the package. This way you will get the color you want. The most used product is a mixture of potassium sulfide.
Step 4. Take the copper piece outdoors or work in a room with good ventilation
Arrange newspapers on the ground to protect the ground from any splashes.
Step 5. Spray the copper with the solution at least twice a day
After spraying the metal, wait about an hour to evaluate the reaction. If it shows early signs of oxidation, continue to wet it every hour, focusing on the spots that seem most reluctant to form a patina. If not, spray the object twice a day until the patina becomes visible. Leave the object outside to speed up the oxidation process.
- If you want to check exactly where the patina should form, scrub these areas with a scouring pad, a brass brush or a cotton swab immediately after wetting them. Put on rubber gloves and put on safety glasses if the solution contains ammonia or other dangerous chemicals.
- If you live in a dry area, cover the metal with a plastic bag or tarp to trap moisture. Help yourself with a frame or other large object to prevent the sheet from coming into contact with the copper.
Method 3 of 3: Use Alternative Techniques
Step 1. Make the copper green and blue with fertilizer
Use a concentrated one to oxidize copper quickly. Mix one part of fertilizer with three parts of water if you want a blue sheen, or use red wine vinegar if you prefer a green tint. Apply the mixture with a sprayer or rag; try to work evenly over the entire surface if you want a natural aged look. In about 30 minutes a patina will develop which will be permanent in 24 hours.
Step 2. Coat the metal with white vinegar
This way you will get a green or blue oxidation. To maintain contact between liquid and metal, you can simply immerse it in a bowl full of vinegar and salt or cover it with sawdust and then put it in vinegar. Close the container for 2-8 hours and check the color transformation regularly. When you are satisfied with the result, remove the copper from the container and allow it to air dry. Use a soft brush to remove solid residues.
Step 3. Create a bright blue with ammonia and salt vapors
Fill a container with 1.25 cm of pure ammonia, take it outside or to a well-ventilated room. Spray the copper with salt water and place it above the ammonia level, resting on a block of wood. Cover the container with the lid and check the process every hour until you get a brown color with blue streaks. At this point remove the object from the bucket and let it dry in the open air, it will turn blue.
- Attention: Always wear protective gloves and goggles when handling ammonia. Do not use old ammonia containers to store food or water.
- The greater the amount of salt, the more vivid the color will be.
Advice
- Mix the solution in a container used only to create the patina and use the sprayer only for this purpose.
- If you have a small chemistry set you can try more complex oxidation blends. Do some research online, but be aware that some combinations may generate an unexpected color.
- The oxidation patina will last longer if you protect it with wax or a specific sealant. Do not use a water-based finishing product if the patina was created with ammonia.
Warnings
- Never combine ammonia with bleach or other detergents or household products.
- If you use ammonia in an enclosed space, make sure it is well ventilated. Beware of contact with eyes.
