Coloring, Bronzing & Patination of Metals

    CRAFTS CLASSES
    TO INSPIRE CREATIVITY
    by Pam Raymer-Lea

    About the Author

    Pam Raymer-Lea is based in Los Angeles. She holds a M.F.A. in film and television, a master's degree in education and a B.S. in fine art. Raymer-Lea has taught a variety of subjects including filmmaking, writing, art, art history and science. She is a jewelry maker and is skilled in a variety of crafts ranging from glass blowing to home improvement.

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    Coloring metal can have a dramatic effect on a piece of jewelry or other metal art. The three basic methods of coloring are patination, applied color and heat. Patination is the reaction between the metal and a chemical that results in colored chlorides or oxides. Patination is hard to regulate and may produce different results every time.

    Things You'll Need

    • Liver of Sulphur (potassium sulphide)
    • Non-metal bowl
    • Plastic container with a tight-fitting lid
    • Small plastic bowl
    • Salt
    • Ammonia
    • Vinegar
    • Torch
    • Flux
    • Alcohol
    • Paper towels
    • Potassium permanganate
    • Copper nitrate
    • Nitric acid (38 Be)
    • Copper sulphate
    • Potassium sulphide
    • Potassium bichromate
    • Alizarin
    • Batteries
    • Anodizer
    • Acid or alkaline solution
    • Titanium wire
    • Titanium alligator clip
    • Standard wire
    • Standard alligator clip

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    Liver of Sulpher is particularly effective in changing the color of silver.

    Dissolve Liver of Sulphur (potassium sulphide) in a non-metal bowl of hot water. Bathe silver in it to achieve a light golden brown to black. Use it on copper to turn it black, or on brass for a deeper gold after a bath of more than 15 minutes. The hotter the water, the faster the chemical works. Try heating the metal, instead of the water, for the same reaction. The longer the metal is in the water, and the more chemical you use, the faster the color changes. Rinse well.

    Copper and brass obtain a blue patina when exposed to amonia and salt.

    Produce a blue patina on copper and brass by exposing it to a tank of ammonia fumes and salt. Find a plastic container with a tight filling lid and another small plastic bowl that fits inside. Spread a 1/4- to 1/2-inch layer of salt on the bottom of the large container. Fill the smaller bowl with at least 1/4 inch of ammonia and set it in the middle of the salt. Bury the pieces you want to patina in the salt, put the cover on tightly and leave it undisturbed for at least two days. Rinse well.

    Accelerate the weathering process of copper and brass with amonia and vinegar.

    Create a green color on copper or brass by mixing three parts ammonia and one part vinegar in a plastic container with a tight fitting lid. Submerge your piece in the chemicals for two days. Rinse well. This method is less reliable than salt and ammonia.

    This is the type of red achieved when flux is heated on copper.

    Heat copper with a torch to create a rainbow of colors. Overheat the copper to create dull gray. Achieve a deep red color by coating your copper with flux and heating on both sides until the entire piece glows red. Use a light touch to get colors other than red. Heat brass to create a rainbow of subtle colors and heat aluminum to gain a rainbow toward the blue end of the spectrum.

    Aluminum can chemically change color to brown or black.

    Color aluminum pieces. Degrease the metal with alcohol on a paper towel. For a brown to black color, mix 10g of potassium permanganate, 25g of copper nitrate, 4g of nitric acid (38 Be) and 1L of water that has been heated to 212 degrees F. Immerse your piece for 5 minutes to get light brown, 15 minutes for dark brown and 30 minutes for black.

    Create a gold or red color on aluminum.

    Achieve a golden yellow color on your degreased aluminum by mixing 20g of potassium permanganate with 1L of water heated to 176 degrees F. Add 5g of copper sulphate for bronze color. Produce a red color with 25g of potassium sulphide, 3g of potassium bichromate, 1g of alizarin and 1L of water that is room temperature or greater.

    A rainbow of colors can be produced on titanium by using an electric current.

    Color degreased titanium with batteries or an anodizer. Fill a plastic container with an acid or alkaline solution. Connect your positive terminal to the titanium using a titanium wire and alligator clip. Use any kind of wire and alligator clip to attach your positive terminal to a rust-proof piece of metal. Put both pieces in the tank and let the current flow. The color change depends on the voltage. Achieve a light yellow with 9 V, light blue with 18 V, deeper blue with 50 V, and bright green at 110 V. Use a torch or kiln to color titanium; heat the titanium to 640 degrees F to color the metal.

    • The acid or alkaline solution used with titanium can be anything from trisodium phosphate to vinegar. Do not use chlorides, nitrates or sulphates, which are toxic when electrified.
    • The chemicals used in patination can be toxic, torches are hot and titanium can spark when it is heated. Use care to avoid injury.

    References

    • “The Jeweler's Directory of Decorative Finishes: From Enameling and Engraving to Inlay and Granulation”; Jinks McGrath; 2005
    • “The Colouring, Bronzing and Patination of Metals”; Richard Hughes & Michael Rowe; 1991
    • Holly Gage: Adding Color to Titanium with a Torch

    Photo Credits

    • colorful rusty metal texture image by Andrejs Pidjass from Fotolia.com