Gold is a precious metal available in various shades of color and different levels of fineness. The value of the jewel or other object will largely depend on its purity or the presence of plating. To identify the quality of a metal object, start by looking closely at its surface. If you are still not satisfied, move on to more specific tests, such as using vinegar. As a final option, you could apply acid to the metal and observe the reaction.
Steps
Method 1 of 3: Inspect the Surface
Step 1. Look for a brand
A gold item will usually have a stamp indicating its type. A "GF" or "HGP" mark indicates that it has a gold plating (so it is not pure). On the other hand, a pure gold jewel could have a “24K” mark or other hallmark indicating its fineness. The branding can usually be found within the band of a ring or near the clasp of a necklace.
- However, be aware that some brands may be counterfeit. For this reason, you shouldn't just look at the brand as an indicator of authenticity.
- The brand may be very small. You may need a magnifying glass to see it clearly.
Step 2. Look for any discoloration on the edges of the object
Turn on a rather powerful lamp and observe the object closely near its light. Turn it over in your hands, so you can examine all sides of it. If you see that the gold appears discolored or missing at the edges, then the item is probably just plated, which means the piece is not pure gold.
Step 3. Look for small spots on the surface of the object
While holding the piece in bright light, do you notice white or red speckles scattered across its surface? These spots may be very small and difficult to detect, so the help of a powerful light and perhaps even a magnifying glass is important. These signs indicate that the gold plating is wearing out, revealing the underlying metal.
Step 4. Bring a magnet close to the potential gold object
Hold the magnet directly over the piece and lower it until it almost touches the surface. If you feel that the magnet is drawn down, then the piece is not pure. The other metals in the object, such as nickel, are responding to the magnet. A pure gold piece of jewelry would not attract the magnet, as gold is not ferrous.
Method 2 of 3: Conduct More In-depth Tests
Step 1. Apply vinegar to the surface and see if the color changes
Take a dropper and fill it with white vinegar. Hold the piece firmly in your hand or lay it on a table, then drop a few drops of vinegar on it - if they change the color of the metal, then it's not pure gold. If the color remains the same, then it is pure gold.
Step 2. Rub your gold object against a touchstone
Place a black touchstone on a table. Hold the gold piece firmly in your hand and rub it firmly on the stone, in order to leave a mark; if this sign is compact and golden in color, then the object is pure; if, on the other hand, it is slight or even absent, then the piece is probably plated or there is no trace of gold.
Be careful with this method, as it could damage your jewelry. You will also need to use the right stone, otherwise the marks will not be clear. You will be able to find a touchstone at an online jewelry store or you could ask a local jeweler
Step 3. Rub your gold on a ceramic plate
Place an unglazed ceramic plate on a countertop or table. Pick up your gold item and rub it against the plate. Check if you see a stripe or mark of any kind - a black line indicates that the piece is not gold or is plated.
Step 4. Test your gold with liquid foundation
Spread a thin layer of liquid foundation on the back of one hand and wait for it to dry. Rub the metallic object on the foundation layer - the authentic pure gold will leave a line on the cosmetic. If you don't see any marks, then the piece is plated or some other metal.
Step 5. Use an electronic gold tester
This is a portable device with a probe pen that you can buy online or at a jewelry store. To examine the piece, apply a conductive gel to its surface (usually the gel is available with the tester). After smearing the gel, rub the pen against the object. The response of the metal to the electrical impulse will indicate whether the metal is pure or not.
Read the instructions that came with the tester to determine the exact result. Gold is a conductive metal, so a pure gold item will have a higher reading than a plated one
Step 6. Insert your gold into an XRF spectrometer
This is a device used by many jewelers to instantly determine the quality of a sample. This method is a bit expensive, so it is not recommended for home use unless you plan to use it regularly. To use the spectrometer, put the object inside it, turn on the device and wait for the result to be read.
Step 7. Have your gold analyzed by an assayer
If you continue to have unclear results, or if you want to verify your result, talk to your trusted jeweler for another professional opinion. An assayer will conduct in-depth analyzes of the metal content. This option may be expensive, so only use it if you think it's worth it.
Method 3 of 3: Run Acid Tests
Step 1. Purchase an acid test kit for a more accurate estimate of gold purity
You will be able to buy one of these kits from a jewelry tool supplier. The kit will contain everything you need and instructions for proper use. Before you begin, read these instructions carefully and check that all components are present.
These kits could be quite affordable when purchased online. The price should be around 27 euros
Step 2. Check the karat rating labels that you will find on the needles
In the kit there will be various needles to test different types of gold. Look at the carat mark on the side of the needle; each needle will also have an example of gilding on the tip. Use the yellow one for yellow gold and the white needle for white gold.
Step 3. Make a notch with an engraving tool
Find a hidden spot on the piece. Make a light engraving on the metal. The aim will be to expose the deeper layers.
Step 4. Put on protective gloves and goggles
It is important to wear thick but tight-fitting gloves, because you are handling acid. For greater safety, it would be good to also protect the eyes. Avoid touching your face and eyes while you work.
Step 5. Put a drop of acid in the incision
Choose the right needle for the type of gold, then direct the needle tip directly over the incision. Push the needle plunger until a single drop of acid falls into the incision.
Step 6. Read the result
Look closely at the incision where you just applied the acid. The metal, reacting, should generate a color change. Usually if the acid turns green, the result indicates that it is not pure metal, but gold plated or even some other material. These kits have different color indications, so read the guide carefully to correctly interpret the test result.
