Ammonium persulfate is one of many compounds available for copper etching, and is often used for etching circuit boards in particular. It is available in a dry or powder form and must be mixed with water to create the etching solution. In addition, the solution must be hot to etch copper efficiently, and heat causes ammonium persulfate to decompose. Therefore, you must mix a fresh solution every time you want to etch copper. Mixing an ammonium persulfate solution is not difficult, but it is important to take proper precautions to ensure safety when handling this chemical.
Put on the gloves, goggles and mask. Ammonium persulfate can cause serious skin irritation and unpleasant or irritating fumes. It can also cause allergic reactions in some people.
Pour 100 milliliters of distilled water into a clean glass container. If you want to use the solution immediately, heat the water. The metric system is standard for the sciences, including chemistry, and working with grams and milliliters enables you to calculate ratios more easily. (see Reference 2)
Put a clean glass container or disposable container for weighing chemicals onto a scale and tare it, or reduce the weight to zero so the scale does not take the weight of the container into account.
Add ammonium persulfate powder to the empty glass container using a clean plastic spoon or a chemistry spoon until you have 10 grams of powder.
Carefully add the powder to the container of distilled water and stir thoroughly with a glass stirring rod. The powder makes a clear solution, so stir until you do not see any powder. Make more of the solution, if necessary, until you have enough to cover the item you are etching.
- Chemistry goggles
- Glass containers
- Distilled water
- Plastic spoon
- Ammonium persulfate
- Glass stirring rod
Adding 10 grams to 100 milliliters of water makes a standard 10-percent solution. This is typical for etching, although you can make a stronger solution if desired, up to about 20 percent. In addition, some companies sell this chemical in tablets that create a 10-percent solution when added to the proper amount of water and do not need weighing.
Always work with clean materials and use glass containers, which have low chemical reactivity. While less dangerous than many other etching chemicals, ammonium persulfate is a strong oxidizer and can have very negative reactions with other chemicals. Work outdoors or in areas with good ventilation to disperse irritating fumes.