Plating is an affordable alternative to crafting your jewellery entirely of expensive metals, but get any of the steps wrong and you risk wasting precious money and time. Here are a few crucial pointers that should not be overlooked:
Ensure surgical cleanliness of all articles and equipment
In all electroplating or colour gilding processes (and also in electropolishing or stripping) it’s essential that all surfaces are chemically clean. If a polished finish is required, the original surface must be polished prior to plating, followed by electrolytic cleaning in a hot or cold alkaline cleaner. Where necessary, an acid dip should follow to remove tenacious oxide films. It is important to note that as little time as possible should lapse between cleaning and plating, since deposits on parts that spend long intervals between stages often do not have good adhesion or as bright appearance as those parts which pass uninterruptedly through the plating sequence. If there is any reason to delay its being placed in the plating solution, the object should be immersed in clean distilled water to prevent the formation of surface oxidization from air contamination.
You can check the quality of your cleaning by doing a simple “droplet test” with your squeeze bottle by drenching the article with clean distilled water. If it runs off in an even film the article has been cleaned properly. If the water disperses into droplets that cling to the surface, this indicates the presence of grease or other foreign substances, and the article should be cleaned again.
Electropolishing and stripping: the temperature is key
If your item first requires electropolishing or stripping before plating, it must be perfectly clean and grease-free in order to obtain a good result. The chemical reaction involved in this process of anodical electrolytical stripping generates considerable fumes and therefore a well ventilated work area and preferably a ventilation hood should be used. Regardless whether you’re after a polished or stripped result, the stainless steel cathode should be immersed up to at least 10cm and the article should be completely immersed in the solution.
The optimum conditions specific to each individual plater’s needs come from ‘play’ (using a spare piece of work) and experience. The general guidelines however are that if the electropolishing / stripping solution is used at high temperatures and voltages (±80°c / ±6 to 15 volts) it acts as a stripping solution and is very effective in the removal of projections or rough surfaces which frequently appear on castings. If used at low temperature and voltages (±40°c / ±3 to 6 volts) it acts more as a polishing solution in refining the surface of the object.
The stripping action should be watched carefully! Once the surface metal is stripped the base metal will be attacked and etched, which may not be desirable. Periodic reversal of the current is sometimes employed to keep the surface smooth.
Buffing and polishing: avoid burns
Buffing and polishing are important steps to quality plating because scratches, imperfections and discolouration are never hidden by the plating and must therefore be removed at this stage. When polishing, remember that a light pressure on the buff or circular brush is sufficient to obtain a good result. Silver is the softest of the precious metals and hence care must be taken when buffing as burns can easily occur. Avoid heavy pressure on the buff, and always use a light polishing compound.
Masking for a two-tone effect
Masking lacquers offer you the possibility of doing two-tone work. Simply cover the part of the article that is to remain the original colour (which you may or may not have previously plated) with the masking lacquer, not forgetting to leave a small section free of the lacquer to which the handling wire is to be attached for the electrical connection. This is because the masking lacquer acts as an insulator. After plating, the lacquer can be removed by rinsing in acetone and a wash-out brush. Finally, rinse in water.
Plating tips specific to each metal can be found on the CPM site in our resources section. Let us know if you’d like to see tips for any metals that are not already there.
