You asked if you "were doing something wrong" when the nickel plate came out dull and not bright. Perhaps it is something you are doing and perhaps it is the solution you are using. First of all, please keep in mind I am far from expert in nickel plating. I work in a small shop, likely not too different from your work area. Almost all the plating we do is rhodium over white gold. Nickel plating is only needed once in a rare while.
Still, I will give you my 2 cents worth. THE SOLUTION. Nickel plating solutions as available in the small quart sizes used by small shops come in two varieties. One is simply called "nickel" and the other is called "bright nickel".
I don't know the specifics but the makers say special "brighteners" are included in the bright nickel solutions. The solutions I have used are not called "bright" but with proper voltage have produced bright coatings on polished metal. There might be something to using the "bright nickel" solutions.
I do not have these solutions in our shop. The additives may help overcome some of the faults we may have in the process. VOLTAGE, AMPERAGE AND TEMPERATURE. What I see from industrial websites and other info in the importance of amperage in plating. Of course, voltage and amps work together in a sort of volt/amp curve.
In small shop setups, amperage is not so controllable as in industrial applications. We must rely on voltage as the guide for proper plating. Most rectifiers of small sizes do not have milliamp gauges and have an almost crude amp meter so unless amps are going much over full amps, like 1 to 2 to 3 amps, we cannot read the gauge accurately. I installed a milliamp meter on my personal rectifier but found little info with solutions or from solution makers to make the gauge very useful. With nickel plating, as I understand it, low amperage is desired.
Voltage recommendations are best used as the ones with the solution you have. Generally, a low voltage of about 2 volts is desired to produce a bright, smooth plate. The item should be agitated in the solution, a little shake is ok. There will be little visible action on the item and only perhaps a few bubbles showing on the anode. This lack of visible action makes the plating more difficult since time in the bath will affect the coating.
Still, do not exceed the recommended voltage for the solution you have on hand. Temperature is recommended from 70 degrees f to perhaps 120 f. I always had the best results at low temps, closer to room temperature. The plate was immersed at the recommended voltage, agitated and removed after about 30 sec and inspected.
Then a following plate was applied with a bit more time allowed to go beyond a simple flash thin plate. Nickel can produce a quite dense plate when repeated and not hurried. Inspection should be done to insure things are not going to grainy or discolored appearance. BRIGHTNESS OF THE ORIGINAL ITEM TO BE PLATED.
Contrary to what some of our customers believe about "dipping" an item in gold, in rhodium or even in nickel, we know we do not dip into hot metal! We dip into electroplating solutions. When active in the plating bath, the metal ions moving to the object follow every curve and crevice in the object. Scratches and dull surfaces will be repeated by the plate. It is imperative that the item to be "bright" plated be polished to the utmost degree. Once polishing is done, the item should be immediately cleaned and readied for the plate bath. You do not want to allow sterling, in your case, any time to develop even the slightest tarnish which would interfere with good plating result.
Yet, from experience, what I have said rings truth. Please be certain the silver item is well polished and cleaned and plated very soon. Be patient with the plating process and do not try to rush it. Too much voltage can cause a rough and dull surface on a polished item.You might want to try an experiment by masking a piece of silver stock with fingernail polish.
Red colored polish is easy to read. Plate an item in the nickel and use a nail polish mask for part of it. Remove the lacquer with acetone and look at the surfaces to compare and note brightness and color difference. This is a good test. You might want to do the masking to preserve silver as unplated silver and rotate a piece of silver stock to plate one end at one length of time and the other at another time allowance or even use multiple plating.
You will have a direct comparison on the same piece of silver which makes reading the differences much easier. ALTERNATIVE. Did I mention palladium already? Palladium solutions are available and generally at a much lower cost than rhodium.
The plate will go on silver directly, for most solutions. The palladium does not have the hardness of rhodium but will provide a tarnish barrier layer to the sterling. This might be attempted. The color is generally bright and in the thin plated layer is close to the original color. Solid palladium has a blue/grayish tint compared to some other metals. In electroplate, the color is just fine in my experience plating on to white gold.
The following web sites offer some but not really important info. When you have time, you might want to check out what is said. PARTS PLATING.NOT JEWELRY. Interesting Info.
After searching the internet, we found a website that mentions buffing to polish. You might try this. Since nickel does plate with a dense layer, often the surface is gently polished then recleaned prior to other plating, such as rhodium. I have done this with success. I polished with a soft brush in a flex shaft machine using a non-abrasive rouge.
The nickel polished from a semi-dull to a bright finish and was dense and thick enough not to be polished away. Polishing of nickel plate is not at all uncommon and should be given a chance.
Victor Epand is the owner of JewerlyGift.biz, a huge online jewelry retailer featuring the largest and best selection of jewelry including personalizable items...