Are you experiencing blackening or powdering issues after gold plating, similar to what Pete described with his coin experiment? Many hobbyists encounter this problem, especially when starting out with gold plating kits. Let’s dive into why this happens and how to troubleshoot it, ensuring you achieve that perfect gold finish every time.
Understanding the Blackening Issue in Gold Plating
Pete, like many newcomers to gold plating, observed an initial success followed by an unexpected blackening of the gold layer. He noted:
“For my first experiment I did the old “copper coin connected to the cathode” test which resulted in a nice shiny golden coin. However, I then left the coin in for a further 20-30 minutes only to find that, instead of the gold plating getting better, parts of the coin were now turning black.”
This scenario is quite common and points to a key aspect of gold plating, particularly with hobbyist kits: plating time sensitivity.
Over-Plating: The Culprit Behind Black Gold
Chris, an experienced gold plater, astutely diagnosed the issue:
“What do the instructions say about plating time? Most of those gold plating solutions sold to hobbyists contain little gold and are therefore very sensitive to plating time. Most are limited to plating times of less than 1 minute (commonly, somewhere between 20-45 seconds, depending on the solution makeup). Otherwise, the plating will look good at first, but then, when left in the solution too long, it will start darkening and will become powdery, as yours has done. The longer you plate, the worse it gets. The black powder is essentially finely divided gold.”
The core problem is over-plating. Hobbyist gold plating solutions, and even many jeweler’s solutions, are designed for a thin layer of “color gold.” They contain a limited amount of gold and are intended to deposit just enough gold to achieve the desired color, typically around 4-7 millionths of an inch.
Alt text: Close-up of a gold plated coin, illustrating a typical subject for hobbyist gold plating, relevant to troubleshooting articles.
When you exceed the recommended plating time, especially at a constant voltage like Pete’s 6V, several things happen:
- Gold depletion in solution: The limited gold in the solution gets used up quickly, especially with extended plating times.
- Poor deposit quality: Instead of a smooth, even gold layer, you start depositing finely divided gold, which appears as a black powder. This is essentially the gold breaking down and not adhering properly to the base metal.
- Weak and powdery finish: The extended plating doesn’t strengthen the gold layer; it weakens it, making it powdery and easily rubbed off, as Pete discovered when polishing his coin.
The Importance of Manufacturer Instructions for Gold Plating
Chris emphasizes a crucial point for successful gold plating:
“Read the manufacturer’s operating instructions and follow them to the letter.“
Gold plating solutions are formulated differently and require specific operating conditions. Key factors outlined in the instructions are:
- Plating time: This is critical. Hobbyist kits often have very short plating times (20-60 seconds).
- Voltage: While Pete used 6V, the optimal voltage can vary. Instructions will guide you.
- Current density: Some instructions may mention current density, which is the current per unit area of the object being plated.
- Temperature: Certain gold plating solutions operate best at specific temperatures.
- Agitation: Some processes require movement of the solution or the object being plated.
Ignoring these instructions is a recipe for plating problems, including blackening, poor adhesion, and wasted gold solution.
Understanding “Color Gold” in Plating
Chris also clarifies the concept of “color gold”:
“These hobbyist plating solutions and most jeweler’s plating solutions are generally designed to only deposit “color” gold, i.e., just enough thickness, about 4-7 millionths of an inch, to “color” the object. Once the full gold “color” is achieved, the part should be removed from the solution.”
“Color gold” plating is about aesthetics, not creating a thick, durable gold layer like solid gold jewelry. It’s a thin flash of gold to enhance appearance. Attempting to build a thick layer with these solutions is not their intended purpose and leads to issues like blackening.
Troubleshooting Steps and Getting Back on Track
To avoid the black gold problem and achieve successful gold plating, follow these troubleshooting steps:
- Consult your kit instructions: Locate and meticulously read the operating instructions provided with your gold plating kit. This is your primary guide.
- Pay close attention to plating time: Strictly adhere to the recommended plating time. Use a timer to ensure accuracy. Start with shorter times and observe the results.
- Verify voltage and current: Double-check the recommended voltage. If current density is mentioned, understand how to calculate and control it.
- Solution condition: Consider if the solution is still usable. If you’ve been plating for a long time or suspect contamination, the solution might be depleted or compromised.
- Provide more information (if needed): As Chris requested, if you’re still struggling, provide details about your kit and solution. Sharing the manufacturer’s instructions or solution details (concentration, price) can help experts provide more tailored advice.
By understanding the limitations of hobbyist gold plating solutions, the importance of plating time, and diligently following instructions, you can overcome the blackening issue and enjoy successful gold plating results in your hobby projects.
