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Homemade Brass Plating for a Bath

Creating brass plating baths is considered as much an art as a science in the finishing industry. That is because brass is a combination of copper and zinc and can form a brass plate over other substances despite significant variations in the types of ingredients in the bath. Even variances in the inputs, such as the amount of current directed through the bath or the pH of the solution, can change some aspects of the final plate. Many finishers adopt a strict formula in order to provide a uniform quality of brass plate, but you can experiment with that formula at home to create different brass finishes.

Process
- There are many formulas for brass plating baths, some dependent on the substance to be plated. The essential process involves dissolving copper and zinc cyanides in either sodium or potassium cyanide. Ammonia is almost always added to dissolve the precipitants of copper and zinc to help form an even plate. Other substances are often added to stabilize the solution or create specific qualities. Direct current is run through the solution after the substance to be plated is put into the bath. The zinc and copper form ions, positive electrically charged particles, that are drawn to the substance to be plated, which forms a negatively charged cathode. The substance to be plated usually remains in the bath for 10 to 25 minutes.
Ingredients
- The brass plating bath contains about three percent total metal. If the deposit that coats the substance to be plated gets too red, more zinc salts will brighten it. If it gets too white, more copper salts can be added. If the solution takes on a blue or greenish cast, it needs more cyanide. Sometimes, the coating can become dull and uneven. When this happens, the addition of arsenious acid will correct it if the other variable ingredients are in sound proportions.
Current
- The amount of current run through the path has a big impact because the two types of metal salts present different levels of resistance to the current. A deposit that is too red can also be corrected by an increase in the current, and one that is too white can be corrected by a decrease in current. For coating ferrous metals or lead, a heavier current is required. The anodes, through which the current is run through the bath, should always be at about the same distance from any cathodes, or pieces to be plated, in the solution.
Heat
- Some substances require a hot bath to properly accept the plate. Temperatures for a hot bath normally range between 130 to 140 degrees Fahrenheit but can go as high as 160 degrees Fahrenheit. For lead, a warm bath of 90 degrees Fahrenheit is usually used. In any bath, but particularly in hot baths, you should watch the specific gravity of the solution, which can range between 5 to -1 degree on the Baume scale. If it gets further into negative territory, the flow of current can be impeded. Add fresh water to bring the specific gravity back into working range.

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