Patina: It's just a change in color of the metal. Beautiful Patinas can be created naturally on the surfaces of the copper due to Oxidation. The copper color changes to Blue or green patina overtime when the metal reacted with Oxygen (Exposes to Air).
The change in color is the natural process happening on the metal like pure copper. Only when the color changes overtime, then it's a PURE copper.
There are several methods to observe whether it's a copper or not.
METHOD 1: COLOR TEST
Procedure: Place Few drops of mixture table salt (1) ,vinegar (1) & water (3) (1:1:3) on the surface of copper . Let it dry as it is for 12-24 hours. Wipe it out using clean cloth.
Result:
Have a close look and able to see the color changes to reddish brown or Orange along with little greenish or blue combination shiny look, it’s definitely copper.
Why the color gets changed?
If the material is copper, it eventually oxidizes from exposure to oxygen, water and carbon dioxide. This creates a color change on surface of the copper.
METHOD 2: SOUND TEST
Procedure:
Hit slowly your copper item against something. You now listen to the sound.
Result:
Real copper should deliver a deep and mellow sound where as other materials produce different sounds.
It’s difficult to judge one who is not familiar with the copper sound.
METHOD 3: MAGNETIC TEST
Procedure:
There is no magnetic power on copper item. If the magnet sticks then it won't be a copper.
When you go for shopping, take a small piece of magnet and check it out before purchasing.
Result: Copper never sticks to the magnet.
METHOD 4: CHEMICAL TEST
You can pass the samples to experts to conduct chemical test to find out the % of copper present in it.
A simple video to clean COPPER Dactylo using Vinegar and Salt Mixture
There are several ways to clean copper using homemade simple solutions. Always ensure to dry with a clean cloth (without any drop of water on it after cleansing).In case any acid or water left on the piece will create uneven splotches and water marks.
Lemon & salt Mixture. Cut half a lemon and add a salt on top of it. Rub it on the copper surface. Rinse with water & dry with a clean cloth.
Lemon & salt paste. Mix lemon juice and salt (or baking soda), rub on the copper with a cloth, rinse with water and dry with a clean cloth.
Ketchup. Apply ketchup all over the area, Leave for 5-10 minutes and rinse clean!
Solution to make & keep. This is one you can make up and store in a glass jar with a secure lid for future use.
Mix ½ cup each of flour, salt and powdered detergent. Add ¾ cup white vinegar, ¼ cup of lemon juice, ½ cup warm water.
Mix well and pour into the glass jar, label and seal.
To use, add a small amount onto a cloth and apply it on Copper surfaces. Use a toothbrush for hard to reach areas.
Rinse with water and rub dry with a clean cloth.
Hot water. In case the copper piece doesn't shine, let us proceed with the heat water treatment. In a large pot, mix 3 cups water, 1 cup vinegar and 1 tablespoon salt together. Add your copper piece into it and allow boiling until tarnish begins to fall way from the copper. Once it cool down completely, take the piece out of it and scrub gently if needed. Take a clean cloth and dry it completely without any drop of water on it.
Vinegar & Salt Mixture: Mix 1 cup of vinegar with 3 cups of water and 1 tablespoon of salt. Add you copper piece on it. Leave it for 5 minutes. Then scrub using hands or soft cloth to remove the stains if any. Wash with water. We will get the copper glow back. Dry with a clean cloth without any drop of water on it.
By following the above simple steps, you will get the polished look of copper for so many years.
But who love the natural color changes in copper, skip polishing and allow your copper age naturally.
References
https://www.thoughtco.com/metal-profile-copper-2340132 https://www.themetalpeddler.com/index.php?route=blog/article&article_id=6