The finishing.com Hotline: Serious Education ... plus the most fun you can have in metal finishing. Ted Mooney, Webmaster
How can I oxidize copper without the use of a patina?
I'm a high school student. For a Design and Technology project I have to design and build a light. I want to use copper rods for my main shaft, which I will try to entwine around each other. But to suit the style of my design, it would be more aesthetic if the copper where rustic, i.e. green. So I would like to know if there were a quick way to oxidize the copper, and create an authentic layer of copper oxide around it, without using any patinas? I have already tried heating small samples of copper, which did turn the copper green for a while, but the oxide ions didn't stick to the copper and so dissipated away again. And on further heating it just created a layer of black carbon (or was it black copper oxide?). Anyway, I then tried bleach, which is working VERY slowly, and also it would not be practical to oxidize 180 cm copper rods in bleach.
So please does anyone have an answer? It would be a great help to know how to turn copper green without the use of a patina, because I will get extra marks for the oxidizing process.
Thanks a lot!Sienna M.
student - London, Great Britain
A. One way is to set it outside and spray it every morning and every night with a mist or acidified salt solution. Time, from 1-2 weeks. A guess would be a couple tablespoons of common table salt, 1 liter of water and acidify with a couple teaspoons of muriatic acid. Check with your facilities folks. Another source would be the chem lab, only here it will be labeled hydrochloric acid. Use a little less of this as it is about 20% stronger.
You could also try straight vinegar. This will form a copper acetate film. This also needs to set outside for the duration. The temperature changes with the humidity and dew seems to accelerate the process.
PS, this solution is relatively safe, but it will slightly etch concrete and it will promote rust on virtually any bare steel within several feet.James Watts
- Navarre, Florida
A. Sienna, there is a nice article in the Metal Finishing Guidebook and Directory on ANTIQUING OF BRASS, COPPER, AND BRONZE by Mark Ruhland of Birchwood Casey. I suspect it would be in a local library, and I'd suggest you start there.
A. The easiest,fastest, simplest way to oxidize copper is to either spray, dip or brush the copper with Sno Bol Toilet Bowl Cleaner [linked by editor to product info at Amazon].
The completed results are within a few hours.
- North Port, Florida
February 25, 2008
A. You might consider flame coloring, Sienna. If so, please see letter 2662 for a discussion and examples.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Amazon Instant Video
January 12, 2009
A. The best way to change the copper to green is to use muriatic acid. You normally use it to clean the grout between tiles. Do not dilute it and apply with a brush where you want it to turn green. It will do it over night. To prevent further tarnishing you can varnish your project.
Bocas del Toro Botanical Gardens - Bocas de Toro Republic de Panama
April 19, 2009
A. I have done a few coppers and have found the best two ways to change the colour is to use battery acid for green and muriatic acid for blue.You can get both without a problem. Muriatic acid is used to clean tiles and concrete. Clean off the copper with either of the acids and then wash with non-chlorinated water, dry and then paint on the acid of your choice. It will change over night . If you want the color permanently lightly brush off the access patina and leave for a couple of days. Then varnish with a satin polyurethane or varnish.
Hope this helps
Bocas del Toro Botanical Gardens - Bocas de Toro Republic de Panama
February 24, 2008
Q. I just bought a Copper Top Table with some scratches... got a reduced price and was confident I could remove them. Found that when I lightly sanded with 600 grit wet/dry paper, I left fine scratches and removed some of the red oxide. Thus removed everything using lacquer thinner [linked by editor to product info at Amazon] and 0000 steel wool [linked by editor to product info at Rockler]. At the stage of oxidizing and want only red not the green patina. Any suggestion on How to Do?John Obrey
hobbyist - California.
July 19, 2009
Q. Will this work on items that have been copper plated? Or chromed and then rubbed down to the copper base? I am building a motorcycle, and wanted to do some of the parts copper and then need the patina look (green).keith price
- puyallup Washington
January 29, 2010
A. It has been my experience the easiest way to achieve the patina you are looking is to use Liver Of Sulphur [linked by editor to product info at Mister Art] . It is available in easy to use gel form on line or at a metal art supply store..Tom McNutt
metal art - Livingston, Texas
December 20, 2011
A. PEE ON IT!CARLOS JUENKE
- Frederickburg, Texas
June 11, 2013
A. I design custom jewelry and was looking for a way to age copper fast and get a nice green patina. After trying several suggestions online with less than satisfactory results I decided to do a little research. I found an article discussing why chlorine will turn a pool green if copper is present in the water. I tried a little something and had terrific results. Here is the list:
1. quart mason jar
2. 3" chlorine tablet
3. pair long heavy duty rubber or vinyl gloves
4. pair safety glasses (goggles are better)
5. several zip lock baggies
7. 2) 3 inch headpins or 2) 4" pieces of wire
8. 2) copper washers thoroughly cleaned and textured if you like
Take the copper washers and clean them with 0000 steel wool, texture them if you like, drill any holes you may want and then wash them in dish detergent and rinse and dry without touching them with bare hands. Your skin contains oils that will inhibit the formation of patina on your copper washers.
Punch or drill 2 small tiny holes in the mason jar top.
Thread a headpin into each hole and make a hook on the end of each headpin which will hold the washers.
Place the mason jar on a level surface outside ( ventilation is important! )
Fill the jar half way with water.
Put the top on with the washers hanging on the headpins above the water. This is a test to make sure your setup is correct. The further away from the water and the closer to the mason jar top then the more they will be affected by fumes. Once you are happy with your setup then proceed.
Take the top off the mason jar and sit aside with the washers on the headpins ready to go.
Put on a long sleeved shirt, your gloves and safety glasses.
Place the unopened 3 inch chlorine tablet in a zip lock baggie.
Take the hammer and hit the chlorine tablet hard enough to break it into several pieces.
Open the zip lock and carefully open the chlorine tablet bag.
Take a couple quarter size pieces and carefully place in the mason jar into the water.
Immediately and carefully put on the mason jar top with the washers suspended above the water.
Depending upon the purity of your copper washers you will see a chemical reaction taking place almost immediately.
You can observe the chemical process as the washers darken then begin to develop a patina.
I left mine in an hour and they had a gorgeous green crust developing. I removed them and used blue scotch pad to buff them before applying a matt finish. I will use a gloss finish next time to see the difference. The green patina filled the textured voids very nicely.
You need to be very careful with the chlorine as the amount you are using was meant for 100s of gallons of water not a half quart. It will burn you severely if you do not take care to protect yourself. Do this in an area where children and pets will not be in danger. Do not stand directly over the top when you take it off, the fumes can burn and damage your eyes. Please, please be careful, be safe and have fun experimenting.
Design and build custom cabinetry, nature photography, steampunk and other jewelry, time traveler - Camarillo, California, USA