It truly amazes me how many people have problems with plating, yet don’t really understand, and sometimes even it seems don’t want to understand why they continue to have problems. I often wonder why this is. Maybe it is because the plating process is quite technical and it can be difficult for a non professional to come to grips with it, maybe it is because good plating – which deposits significant amounts of precious metals on your items is actually quite expensive, and it might also be because most people do not have access to equipment which allows you to actually test the quality of your plating.
I would like to, in easy terms today talk about what is needed to get a good plating result, and along the way try to give some pointers that might help to de-mystify plating and give you a better understanding of the plating processes and how you can work with your plating supplier to get a better result, – and also how to keep him honest! A quick little story here, I had somebody come to see me last week with an item they claimed was plated at 10 microns and it cost X, but they were distressed as the quality was not good!
Firstly plating at 10 microns is unheard of and totally unnecessary, and after looking at the item and a quick calculation of the surface area x 10 microns I could see that the value of gold, if deposited at 10 microns on the total surface area of the item, would have been more than 10 times the price this particular person paid their plater for the item…! My guess from looking at the item was that there was less than 0.5 of a micron thickness there… It is important when buying plated items that you have some understanding of how to get the quality you want and at the correct price, a little bit of knowledge here can really help you make better choices.
Good plating quality actually starts before you start plating, so let’s go back to the beginning and walk though the plating processes and see where the quality pitfalls are and what we can do to avoid them.
Plating or more specifically electro-plating is the chemical bonding of ions of one material onto ions of a substrate material, (in our case it is usually, gold, silver, or rhodium onto a silver or brass substrate) using electrical current at a specific voltage and amperage to facilitate the correct process. The most important requirement of this process is that the plating agent and the substrate can come into direct contact with each other, this means fresh clean metal surfaces. Oxidized surfaces effectively present a barrier to the plating process. So freshly polished items, well cleaned, ultrasonically and steam cleaned, and a good degreasing process are absolutely essential if you are going to get a good plating result, be aware, oxidation (especially on brass!) starts the very second polishing stops, so how you look after your items after that final polish is extremely important if you want to get good results. A rule of thumb, no longer than 24 hours from polish to plating, and if you are able to reduce exposure to oxygen of your jewelry in any way possible – do it! Contact with oxygen in the air causes oxidation/tarnishing on the surface of your items and create a barrier to plating, the plating will not adhere and will rub off, or even in bad cases flake off very quickly.
Now we get to the plating part and I will try to keep it simple and not get lost in technical mumbo jumbo. The big point here is plating is not jewelry making! It is chemistry! And just like you would not employ jewelers in a pharmaceutical laboratory you should also not have jewelers in your Plating laboratory, you need… Chemists! People who are qualified to mix chemicals correctly, calculate parameters for voltage and amperage to ensure you get the correct and specified plating thickness, analyze results, rebalance chemical solutions etc… to be able to ensure your plating quality comes out with stable color and thickness time and time again. Hit and miss quality does not work!
To achieve that little list above requires some complex chemical analysis and calculations, way beyond the scope and knowledge of a jeweler, it amazes me how many times I see jewelers trying to do plating. Another point I must bring in here also is health and safety, plating chemicals are hazardous, highly acidic or alkaline and therefore highly corrosive, and some are cyanide based, these chemicals should only be used by professionally trained lab workers and in a secure clean and well ventilated lab, and with all persons entering that room being well briefed and aware of the risks, and all wearing correct protective clothing. Equally important here is your ability to rebalance or replenish your chemicals, not only does this save you money but it also means you are not throwing highly toxic matter down the drain when your plating results become not so good. It scares me to think of how many small non-trained platers around the world do this and the risk to humans and the adverse effect on the environment it creates.
Plating solutions are comprised of the metal to be added to substrate in ionic form and a liquid conductor solution, when you plate to remove metal ions from the solution – they adhere to the substrate, and so your metal ion concentration in the solution reduces, and the concentration of the toxic conductor solution increases, a professional chemist will be able to analyze this and add more metal ions to re-balance your baths, and keep your plating quality consistent from day to day, a non professional will not have the chemical knowledge to enable him to measure his solutions and replenish them, they will either wait until they see a drop in quality and randomly add in more metal ions, which results in big variations in quality, or they will throw out this old solution and buy a new one! Wow!! Expensive and dangerous. – A note here, when disposing of your solutions it is important to work with a certified hazardous goods neutralizer and disposal contractor. And remember to store all chemicals both new, and those waiting for disposal, in double walled safety containers under lock and key and in a controlled environment. You should really check to see if your plater can do this and follow through to see that they are performing these procedures correctly. If you are concerned, you should ask to visit the workshop and see for yourself, if they don’t allow this, then the chances are high that they are not following the correct operational procedures.
Another key point in getting good plating results is investment in plant, good machines and good chemicals, and this does cost money. Using small plating baths or beakers is OK if your plating is just being done to change the color of an item but if you are looking to get (and selling) micron quality plating you need to use a lager bath – minimum bath size is 25 liters. Any smaller than this and you will get what is called shadowing, this is where the electric current you send from an anode suspended in the bath is shadowed from reaching certain parts of the items being plated. In a small bath you can only fit one anode which delivers current, and like the sun, it shines on one side of the item, this item plates thicker and the other side which is in the shadow plates less, in a larger bath you can place multiple anodes in the bath and prevent shadowing. Also it gives you space to put your items to be plated on a moving arm that moves back and forth though the solution during the plating procedure and further enhancing a uniform deposition of plate on the surface.
But as you can image to set up a machine like this costs some money, and the real kicker is that to be able to plate at micron quality you need to suspend around 5 grams of gold per liter of solution, so for a 25 liters bath that’s 125 grams of gold and a $ 50.00 gold market that is $ 6,250.00 of gold floating in your bath…You can do the maths on 100 liters bath!
Which brings me to the next point which is how can you tell how thick your micron plating really is? Your supplier tells you it is 3 microns, and you sell it to your customer as vermeil quality, but is it? How do you know, do you just have to take your suppliers word on this, and the answer in most cases is unfortunately yes, unless you or your supplier has the budget to buy an AAS (Atomic absorption spectrometry) machine, and last time I looked the cost was around $ 250,000.00. This machine will accurately be able to give you a reading of the composition and thickness of your plating and at the same time the composition of the metal base. This is really the only accurate way to test, and if your customer does this test and your product does not reach the level, your guarantee then you have a problem. This is one of the reason many suppliers will not sign a guarantee document on plating thickness. We don’t have such a machine… yet! So the way we get around it is by using very accurate scales, accurate to 0.0001gms and then we do calculations. We weigh the item before plating and after plating and then we know the difference in weight is the amount of gold deposited, which we then need to divide by the surface area (in mm2) to get the actual thickness of the plating (doing it this way I can assure you, you don’t just need to be a chemist but also a mathematician!) If a customer is asking for say 3 microns we can use this system and be reasonably accurate say within 10% and as we only charge based on weight difference i.e. the value of the gold deposited, our pricing is correct, but I am not brave to guarantee this as 3 microns… It might be 2.8 it might be 3.2, the big difficulty here is actually calculating the correct surface area plated, especially on items using chains or with filigree or repousse style textured work. So if you want a guarantee regarding the micron thickness then we need to work on the safe side: if you want 3 microns guaranteed then maybe we need to set our plating parameters to 3.2 its better to be a little bit safer and with a better quality than having a lawsuit!
However if you are just looking for a good quality level to satisfy your customer without a guarantee then we can analyze your item and agree on what thickness will give you the quality level you want at a price that suits your market. As a rule of thumb items like rings and bracelets receive more wear and tear and need a higher micron level than say earrings and pendants, But no matter how much care you take and effort you put into it, you will always have that customer who will not follow your care instructions and will lay the new concrete driveway wearing your lovely plated ring on complain… but I do hope this letter will help you to make better decisions with regards to plating production and you end up with less of those complaining customers!
Many good wishes,
Ben