Caring for Bronze
We are often asked how to care for bronze and the answer isn't straightforward because it depends on the type of look you want. For instance some want the character of aged bronze, some want the green corrosion, some want shiny gold. Whatever you want, this guide is for you.
Bronze is a metal that is alive. It has character, it grows blemishes, it ages, it reacts to its environment. Take for example the Crab Claw Bottle Openers below, the one on the right is how they look after they have just been polished on our polishing machines, the one on the left is what they look like if they have been used for a few months. The one on the right looks silver in comparison to the one on the left. In person, the one on the right is a bright gold color and the one on the left has the color of an old brass key.
Leave our bronze outside for a while and you get a completely different result. The below photo is one of our 35cm Mud Crabs that has been outside for over a year as a garden ornament and it has held up incredibly well. It is still highly visible in the garden, creating conversations whenever a guest sees it.
You can see the greeny white corrosion around the eyes and edges of the shell and the different colored spots from the tree sap, rain, bird droppings and other corrosive materials dropping onto the crab.
We have tested the impacts of ocean water on our bronze and it has a big impact. We submerged a number of bronze pieces in ocean water for a number of hours and then let them dry and left them outside in a humid environment. The level of corrosion was approximately 5 times faster than our bronze being left outside in the elements in a humid environment. Unfortunately at the time of writing this article, we cannot find the photos.
All of our bronze can be bought back to a brand new mirror finish gold using materials you can purchase from your local hardware store of grocery store.
To remove any green corrosion caused by the copper, you can use vinegar. We recommend mixing some vinegar and water and either wiping it on the bronze with a wet cloth and then washing it off once it has done its job or spraying the vinegar onto the bronze and then washing off the vinegar. You do not want to leave vinegar on your bronze or it will leave marks that you will need to polish out.
If you have an aquarium, you can leave your bronze underwater as an ornament. There have been comments about the copper having an impact on water quality for the fish so we tested that. We put several of our pieces of bronze in an outdoor pond for several months. Whenever it rained the pond got a water change. As far as we could tell, the fish were never impacted and they continued to breed and feed around the location.
Brasso is a great way to polish your bronze back to mirror finish shine. An example of what a bottle of Brasso looks like is below. Simply follow the instructions on the bottle.
Sometimes you get a piece of Bronze that has been very corroded. This can happen by leaving bronze underwater for a long time, outside for a long time or with certain chemical processes.
A good example of very strong, hard to remove corrosion is the heat and chemical process of corroding the bronze in a very specific way to give it color and protect it. We use this process for all the bronze that is brown colored, like the Cyclist below.
Removing the heat and chemical treatment from this cyclist can be done in several ways but the one we would recommend is electrolysis. You could remove the brown by sanding and polishing and that would take many hours and you would be removing significant amounts of the metal. Electrolysis only removes the tarnished brown from the outside, leaving all the metal.
To use electrolysis on bronze, you scrunch up some aluminium foil and put it at the bottom of a non conductive bowl (plastic/glass/ceramic) that can hold your bronze. Put the bronze on top of the aluminium foil, making sure there are gaps underneath your bronze/aluminium for liquid we are about to pour in.
Mix up enough hot water, table salt and baking soda that when poured into the bowl with your bronze and aluminium, it gets covered. Pour the water/salt/baking soda mix into the bowl.
Leave it to sit for a few hours and test to see if the corrosion rubs off easily. If it does, then buff it off using Brasso and a soft cloth. If not, put it back in the water/salt/baking soda mix for a few hours. For highly corroded bronze you can leave overnight or if you are really an expert, you can add 12v electricity