The finishing.com Hotline -- Serious Education ... plus the most fun you can have in metal finishing
I am painting on copper with some copper remaining unpainted. I want the copper to oxidize and and add a natural color to the painting. After the muriatic acid do you have to rinse the copper with water? If so, do you rinse right after the acid treatment or after it oxidizes?Daniel Root
- New York, New York
Did you ever find an answer to your question? I am also looking for the right oxidizing agent. I would love any insight. Here is another answer I found that may help.
I don't yet know if this works but while looking for the answer to the same question you both have I came across this. I will try it and I hope I have helped you guys out. Brushing the copper sheet with a dilute solution of Sulfuric Acid [H2SO4] will form copper sulfate, the aqua blue tint seen on old copper [due to the action of acid rain]. Use protective gloves and eye protection (goggles) and adult supervision [if necessary]. Sulphuric acid is available from automotive supply centers as battery acid. Start with a dilution of at least five parts water to one acid. ALWAYS ADD THE ACID TO THE WATER WITH STIRRING NEVER ADD WATER TO CONCENTRATED ACID [it could explode in your face]. Brush the solution on and wait a few moments for results. You'll have to experiment a bit to get the effect you seek. To stop the coloration, rinse the acid off with a lot of fresh running water. Felicity Stevenson, Australia
Hope this helps,JD [last name deleted for privacy by Editor]
- Newport Beach, California
- Ed. note: for those who remember best with rhymes --
- "Do as you oughta [spoken with a Kennedy accent]
- Add acid to water".
I am a 21 year old student and artist, and I am preparing a similar action at my home studio in Michigan. However, I am going for a particular end result... Malachite. I know that it is made from oxidized copper (thank god for high school chemistry), but is COPPER SULFATE the same thing as Malakite/Malachite? (sp). I believe that it is the same reaction, but perhaps, if it isn't, is there another method, aside from Sulfuric Acid, to oxidize copper, or at least attain a similar action?
And, is a patina finish, the same substance as well, of Malachite? Does the patina finish have anything more to do with the reaction from the sulfuric acid? Is that why our externally-placed copper will eventually turn green faster than an indoors copper piece will brown? Perhaps Sulfuric Acid in acid rain?
Thanks again!Will Thompson
- Holly, Michigan
February 11, 2008
To Will Thompson: Actually, I believe that Malachite is a stone which is slightly rare. I happen to have a small carved pyramid of Malachite. Perhaps the green coating (copper sulfate) is the same as Malachite, just in a different form? I don't know as I am very young and probably completely wrong. So while I don't think that you can create Malachite, you most definitely can acquire it and use for many beautiful pieces of art. I hope someone will correct me if I'm wrong.Matthew Melander
- Saint Louis Park, Minnesota
March 27, 2010
To William Thompson
just read this distinction of oxidised copper
rochantite, a green, hydrated copper sulfate, Cu4SO4(OH)6
malachite, the green, hydrated copper carbonate Cu2CO3(OH)3
azurite, the blue, hydrated copper carbonate Cu3(CO3)2(OH)2
hope that helps
- Exmouth, Devon, England
I am a young student in an art class. Our class is trying to find a formula that oxidizes copper without using sulfur in it. Can anyone help?Aubrey S [last name deleted for privacy by Editor]
- New York City, New York
The blue/green patina of old copper roofs, etc is copper sulfate, so sulfur is a necessary ingredient. The only way to achieve it in a reasonable amount of time (that I know of) is with a dilute solution of sulfuric acid (battery acid.) Depending on how strong the acid solution is the formation of copper sulfate will take anywhere from minutes to years. A solution dilute enough to form copper sulfate in a few days is pretty safe. Even if you get it on your skin it won't burn if you wash it off right away. Perhaps your chemistry teacher would enjoy participating.
The dark brown color of old pennies is copper oxide. That's pretty easy to achieve just by heating the copper in an oven for a while. You'll have to experiment to get the effect you're looking for.
- Middlesex, New York
I have for years used a solution of sodium dichloro-s-trazinetrione and water- common chlorinating concentrate for hot tubs or pools. brush it on 2 or 3 times and let it sit outside. much easier than sulfuric acid, not to mention safer.Thomas Licrem
- Portland, Oregon
About a year ago I found this info on oxidizing copper online:
Mix white vinegar with as much salt as will dissolve in it. Heat to barely tepid. Paint copper with it and let sit for 24 hours. Wash with warm water until it's the right color.
Wax or clear coat it or heat in oven on clean cycle.
I took some copper wire, knit it into a square and coated it with the vinegar/salt mixture and let it sit. It created a blue/green crust on the copper that's quite beautiful.
I did not wash, wax or heat it, so I have no experience with those steps. Perhaps that's the next try.
- Boulder, Colorado
Your site has been so helpful to us in doing our scientific experiment. We were looking for the best found at home solution that will oxidize copper the fastest. Although we planned to use copper sulfate acid, we were not able to get a hold of this substance. These are our results: the salt water solution started changing the copper the fastest (within 3 hours for some of our trials) but then it almost stopped and green particles in the water just settled on top of the surface of the copper. We also used bleach. It took longer to start oxidizing but it is now completely green (we started our experiment about a month ago, although it may have finished before that time). However, the following result was completely unexpected. The white vinegar CLEANED the copper to make it cleaner, shinier, and even farther away from turning and being green than when we started our experiment. We are just sending this to thank you and your site for all of your help and to let people know about our results.
Sincerely, Rose and Shane
- New York, New York
I built a cedar & copper pipe structure in my yard & want to try the bleach approach to oxidizing the copper green. Can you give some details on the dilution & how long you left it on? Mine will of course be out in the rain. Thanks.Springer Hunt
- Seattle, Washington
March 28, 2009
How do you wax oxidized copper? I purchased a necklace where someone oxidized the copper, designed it with colored pencils,and then waxed it. What product do you use for this?Janet Plumb
- Norton, Massachusetts
July 6, 2011
I have successfully oxidized copper using lemon juice, vinegar and salt, and am going to try it today with muriatic acid. Using the vinegar and salt worked great to form all three copper minerals - malachite, azurite, and chrysocolla. The only problem is that these form on the surface of the copper piping that I used. Actually I tried an elbow joint of copper making it so the two ends were up and the salt and vinegar could sit and evaporate - this produced some nice small crystals of azurite, but I thought if I added more vinegar and salt (I almost forgot, the water should be warm initially and the salt really needs to be stirred into the vinegar) the crystals would grow bigger - they disappeared and only malachite was left over.
This method will produce the malachite, azurite, and chrysocolla guaranteed - it takes a little patience. I used a spoon to drip the mixture over the copper and at first it oxidized by blackening parts of the copper. I continued to alternately add the mixture - stirring it each time thoroughly - and was rewarded.
When I said this was a process that forms the minerals on the surface I meant that the process does not oxidize through the copper. It is on the surface and will fall away as it dries. Not all falls away, though it doesn't take much to bump the copper and have flakes of malachite break away exposing the copper underneath.
I am currently conducting an experiment using pine needles to see it that works, and if it works better than the salt and vinegar. Malachite, chrysocolla and azurite form in cool damp environments over long periods of time naturally underground. Do some experiments and add to your knowledge of this cool process. I have learned a lot from this process and continue to pursue different experiments - I have a lot of fun and anxiety trying to make my own minerals, but that is part of life. If you are a painter, the salt and vinegar method work great to form the malachite that can be used for painting - though I am not sure if you add water to it and paint away, or if there is a process to making the paint. The only bad point is that the malachite might smell like vinegar lightly.
Lastly, once the malachite and other minerals form they are not permanent - adding more of the mixture to make it look better only washes it away. The process is to add the mixture, then let it dry, check, add the mixture and let dry, and repeat till you get something you really like.
Create the mixture, drip on some copper piping, joints, or sheets of copper. Ideally you should immerse any of these in the liquid after thorough stirring and let it evaporate and I think you will get the best results. Hope this helps!
- Lookout, California, USA
July 27, 2013
Miracle Gro plant food works well for me to turn it green. Mix it strong ... tablespoon to quarter cup hot water. To turn it black, I've always used sulfur flour in a zip lock bag. Shake article and let it set for 24 hours and wash it in tap water. It's dry and doesn't create a terrible smell.Elizabeth Spring
- Mountville, South Carolina, USA