Take a lemon or lime, squeeze it into a bowl and remove the seeds from the juice. Take a clean, soft cloth, dip it into the juice, and then rub it on the copper item.
Using the leftover peel is especially helpful in cleaning the nooks of the copper item. Rub it directly onto the copper item. The peel contains fibres of the fruit, which carry sufficient juice for cleaning. This process can be very effective on its own too, without a cloth.
If additional polishing is needed, salt may be used in addition to lime. Once the item has been covered with lemon/lime juice, apply some salt directly onto the copper. Gently rub it on the copper surface using a soft cloth; table salt and Himalayan rock salt will work best.
It is important not to let the salt sit on the copper for long, because this can cause a reaction and dark spots may appear on the item. Make sure to continuously rub the salt all around the vessel with the cloth once you apply it.
Once your item is clean to your liking, you can rinse with water and pat dry with a clean cloth.
Tamarind Cleaning Method
Another effective, all-natural copper cleaning method is to use tamarind. A sufficient quantity of tamarind that can cover the surface of the copper item will be needed.
Remove the tamarind from its packet and separate and discard the seeds. Soak the seedless tamarind in a bowl of water for 20 mins. Squeeze the tamarind using your hands so as to mix the pulp with the water until it achieves a paste-like consistency. Strain the leftover tamarind water so only the paste remains. Keep the tamarind water aside; don’t discard it.
Apply the tamarind paste to fully cover the copper item. Let it sit on the copper item for 20 minutes. The tamarind will dry out onto the copper; this is okay. After 20 minutes, take a soft sponge and rub it on the dried tamarind paste to loosen the paste off of the copper item. Rinse with water and pat dry with a soft towel.
To clean the inside of copper bottles and vessels, you can pour the tamarind water inside. Make sure you have enough tamarind water to fully cover the sides. Let this sit for 20 minutes. This can be done after the paste has been applied to the outside. Once 20 minutes have passed, you can use a brush to rub the inside of the vessel. Rinse with warm water and pat dry with a clean, soft towel.