Electrolytic etching, also known as electro-etching or anodic etching, is an alternative etching technique that doesn't involve the use of dangerous acids such as nitric acid, hydrochloric acid and ferric chloride. The method using electrolysis is more environmentally friendly. The process of electro-etching was first mentioned in 1855. The technique allows you to work on small sections of the plate at once and repeat the procedure as many times as needed until you obtain the desired effect.
Things You'll Need
- Pencil or crayons
- Mask, gloves, goggles
- Battery or car battery charger
- Metal plates
- Plastic container or glass tank
Sand the metal plate on which you plan to create your etching with a fine-grit of sandpaper, or a coarser grit, depending on the effects you want to obtain.
Clean the metal plate with turpentine on both sides and dry the it to remove any fingerprints or grease.
Apply varnish on the side you sanded. Draw on the varnished side. Use a pencil for precision drawing or crayons.
Get another metal plate to use in the electrolysis. The plates should be made of the same metals to reduce the chemical effects during the electrolysis. Clean this plate with turpentine to remove impurities and grease and facilitate the electrolysis.
Place the plates in a plastic container with the lid cut off, or a glass tank if the metal plates are larger, that contains an electrolysis solution and ensure that the plates are parallel. The solution should contain the same metal the plates are made of. For instance, if using copper plates, use a solution of copper sulphate. Use 1.35 pounds of copper sulphate powder in 1 gallon of water.
Connect the metal plate you want to etch to the positive pole of the battery or a car battery charger. This is known as the anode. Connect the other metal plate, which is the cathode, to the negative terminal.
Turn on the current source. The solution conducts electricity and the positive ions of copper from the solution draw towards the cathode, while the negative ions of sulphate will be attracted by the anode. The ions of sulphate attach to the copper plate that contains the drawing and corrodes it, having a similar effect as acid. The copper ions will be deposited on the cathode.
Switch off the current source once your plate is etched and remove the plates from the tank. The amount of time it takes for the ions to corrode the plate depends on the size of the plate and the composition of the solution you use.
Tips & Warnings
- Place the metal plates at a distance of two and a half to four inches in the solution.
- Even if copper sulphate is not toxic, protect your hands with gloves when you handle the metal plates.
- Use zinc plates, which are less expensive than copper or steel, but ensure that you use a solution of a suitable electrolyte such as zinc sulphate. Zinc sulphate is more dangerous than copper sulphate, so protect your skin and eyes.
- If using steel plates, opt for a solution of ferrous sulphate or ammonium ferrous sulphate.
- You may switch off the current at any point during the process and turn it back on in case you cannot supervise the electrolysis or have other engagements.
- You may reuse the electrolyte solution for several years because the electrolysis doesn't make the solution weaker. Etching acids can be used only a few times because the acid weakens with each use.
- Store the electrolyte in sealed plastic bottles.
- Never use metal tanks for the electro-etching. Use only glass or plastic tanks.
- Don't inhale copper sulphate powder or other powdered sulphates. Wear a mask when handling these powders.
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