Cleaning Badly Tarnished Brass, Bronze and Silver




About: I'm a biologist interested in all things sciency. I love to figure out how things work and to make my own stuff, be it food, woodworking, electronics or sewing.

This is a easy way to electrochemically clean up brass, bronze and silver items that are badly tarnished.

I have used it quite a bit to clean up boat hardware and items I have picked up while diving.

The method is simple, and leaves you with a nice clean item without having to do much work.

Brass, bronze and silver tarnish because the metal reacts with compounds in the surroundings. This can be oxygen, sulfur compounds, carbon compounds or chlorides.

The tarnishing actually preserves the metal below by sealing it in, so it can not react further with the surroundings. This is the effect that protects statues, and roof cladding that are exposed to the elements for centuries. Sometimes, however, we wish to remove this tarnishing, like in the example of the bronze handle pictured here.

One way to remove tarnishing is to use abrasives like sand paper or polishing creams. Any such mechanical polishing removes some of the metal every time you do it. This can be seen on old silverware, where the patterns and engravings are usually rounded and have lost detail.

The electrochemical way of removing tarnishing, that we use here, is gentler in this respect. In short terms it turns the surface metal back to its original state by removing only the compounds that reacted with it in the first place.

This is a good way to clean up detailed items, where mechanical polishing could cause damage. It could also save you a lot of polishing work if the metal is badly tarnished.

The simple theory behind this method is that different chemicals have different affinities toward each other.

Aluminum has a higher affinity for the sulphur, oxygen and chlorides mentioned above than brass, bronze or silver does, so when you put them in contact with each other, the atoms are going to recombine. In the end, you get tarnished aluminum, while the tarnish is removed from the brass, bronze or silver you started with.

To help the reaction run, we add salts as reactants, and use hot water to speed things up.

Be aware that this method removes all of the tarnish on your items, so on silver, you will also loose the tarnishing in the deeper parts of patterns and engravings.

Most of you have probably tried cleaning copper coins in ketchup or cola at some point in your life. This is a different type of reaction. In both cases the oxidised metal will react with the acid. For household use this is usually acetic acid (vinegar) citric acid (lemon juice) or tartaric acid. This is a very efficient way to remove tarnish, but similar to polishing, it removes metal and should be used with care on delicate objects.

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Materials

Non-metal container
Aluminum foil
Baking soda

Table salt

Hot water



Dishwashing soap

Use a container that is not made of metal. This is to ensure that your items don't react with the container. Glass, plastic, porcelain or enamelled containers are super.

Step 2: Start the Magic

Crumple up som aluminum foil and put it in your container.

Put the item you want to clean on the foil. The metals need to be in direct contact for this to work. For larger items, like this handle, pack the foil around it, so you get a larger contact surface.

Mix baking soda and salt with hot water and cover everything with it. The proportions are not crucial, but about 1 tablespoon of salt and 1 tablespoon of baking soda to 3 dl water should do the trick.

Lightly tarnished objects should clean up in a few minutes, and you just rinse them of and dry them.

For more heavily tarnished objects, you just have to give it some time. You will see tiny gass bubbles rising from the metal as an indicator that the magic is happening.

Now, the bronze handle I have used here is an extreme case. It has probably been laying on the sea floor for decades, and in addition to the tarnishing, it is encrusted in the carbonate shells of marine organisms and other forms of grime. This kind of cleanup requires some extra juice.

In this case, I also added some vinegar and a little dishwashing soap to the water.

The vinegar serves two purposes in this case. The first is that it dissolves the carbonate shells formed by different creatures over the years. The second is that it removes some of the tarnishing by reacting with the metal. In a solid object such as this, I'm not worried about the tiny amount of metal removed by this process.

The dishwashing soap is just there to help remove residues of oils.

Even this heavily tarnished and encrusted handle only needed three hours in the mixture to clean up completely.

As you can see in the third picture, it looks pretty much the same upon removal from the bath. The difference is that the grime no longer sticks to the metal. On the forth picture I have simply rubbed the grime of under running water with my fingers, and on the last picture, I have removed the last of it with a scrubbing sponge to reveal a nice and shiny bronze handle.

Instead of hours of polishing, this required less than five minutes of actual work to clean up.

This method does not leave you with a shiny surface in the end. To achieve that, you have to do some final polishing.

Trash to Treasure Contest 2017

Participated in the
Trash to Treasure Contest 2017

1 Person Made This Project!


  • Made with Math Contest

    Made with Math Contest
  • Cardboard Speed Challenge

    Cardboard Speed Challenge
  • Multi-Discipline Contest

    Multi-Discipline Contest

10 Discussions


4 weeks ago

vinegar in with the bicarb soda... for the heavily calcified bronze...??? Doesnt that simply give a neutral mix again?


Question 1 year ago on Step 2

I have an old ships steering wheel that I picked up from the sea bed that is very badly tarnished. It has a lot of wood in it so I can’t submerge in compounds. Is there a paste I can make to put on the brass parts?
I also have brass port and starboard lanterns that are in need of serious cleaning

1 answer

Answer 1 year ago

If this is an old steering wheel that has been in seawater for some time, I would consider seeking professional help in conserving it, and keep it in freshwater in the meantime. Crystalising salt can utterly destroy wood that has been submerged for a while. Another thing that tends to happen with submerged brass is that the zinc gets washed out of the alloy, leaving it brittle. Worst case, this makes it brake apart. Best case, it just pits the surface. I have cleaned up some badly tarnished items by applying a paste of vinegar, salt and flour. Wash of the paste after a while, and reapply as needed. This is not the electrochemical reaction described above though, just the acid removing the tarnished metal.


2 years ago

Your instructable really helped. Thank you.

I bought this ring in 1974 at the Spokane Worlds Fair. You can tell its age by the hippie-dippie shape of the letters. I haven't been able to wear it because it's brass and it turns my finger green. I am planning to nickle plate it, but I have to get it clean first. I've got a bit more work to do…

before and after.jpg
1 reply

2 years ago

Great article! I attach a photo of a brass bell. It's about 9" round. I have done 10 or more of the vinegar/salt/flour mix and still, as you can see, have a very dirty piece. Should I use your method?

Sould I use your

1 reply

Reply 2 years ago

No picture visible here. As mentioned, the electrochemical method is very gentle, so it will not harm the bell. Are you certain there is nothing on the bell that prevents the vinegar from working? I cleaned up a large bronze bilge pump some years ago, and it required a lot of work as there was a lot of oil on it that helped preserve the tarnish.

Eric Brouwer

2 years ago

Thanks for sharing this. Always nice to have more options.

I usually use the following non-abrasive method to clean copper, bronze & brass:

1 Packet tartaric acid (found between baking aids)

10ml Dish-washing liquid

300ml warm water.

Mix all into a plastic container.

Leave until shining (2 - 4 hours)

1 reply
schouwEric Brouwer

Reply 2 years ago

It is always good to have different options available. :-)

The tartaric acid option also removes some of the metal from the item you are cleaning, so for finer details it might not be the best option.


2 years ago

For a high polish use something like Brasso (or any proprietary metal polish) and cardboard - ideally corrugated box stuff. It is very slightly abrasive and gives a deep shine, without excessive wearing