Colouring metal can have a dramatic effect on a piece of jewellery or other metal art. The three basic forms of colouring are patination, applied colour and heat. Patination is the reaction between the metal and a chemical that results in coloured chlorides or oxides. Patination is hard to regulate and may produce different results every time.
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 colour changes. Rinse well.
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.
Create a green colour 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.
Heat copper with a torch to create a rainbow of colours. Overheat the copper to create dull grey. Achieve a deep red colour by coating your copper with flux and heating on both sides until the entire piece glows red. Use a light touch to get colours other than red. Heat brass to create a rainbow of subtle colours and heat aluminium to gain a rainbow toward the blue end of the spectrum.
Colour aluminium pieces. Degrease the metal with alcohol on a paper towel. For a brown to black colour, mix 10g of potassium permanganate, 25g of copper nitrate, 4g of nitric acid (38 Be) and 1L of water that has been heated to 100 degrees C. Immerse your piece for 5 minutes to get light brown, 15 minutes for dark brown and 30 minutes for black.
Achieve a golden yellow colour on your degreased aluminium by mixing 20g of potassium permanganate with 1L of water heated to 80 degrees C. Add 5g of copper sulphate for bronze colour. Produce a red colour with 25g of potassium sulphide, 3g of potassium bichromate, 1g of alizarin and 1L of water that is room temperature or greater.
Colour 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 rustproof piece of metal. Put both pieces in the tank and let the current flow. The colour 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 colour titanium; heat the titanium to 337 degrees C to colour 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.