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How To Test Gold, Silver, & Platinum
Everything You Need To Know About Testing Precious Metals Check out the DETAILED TESTING GUIDE For More
Tools You Will Need
Get all of your testing tools out and ready. You will need your testing acids, testing stone, jewelers loupe, needle file, & rare earth magnet (optional). Take a look at our DETAILED TESTING GUIDE for a description of each tool and how they are used.
Finding Manufacturers Markings (Hallmarks)
Jewelry manufacturers are required to place a small stamp on their items showing the purity of the precious metal. This is called a Purity Hallmark. Many times the actual karat marking is listed, but sometimes you will see a number (ex. 417, 585, 750). This represents the percentage of gold in the piece (ex. 18K may show 750 = 75.0%). Reputable costume jewelry manufacturers will also stamp hallmarks showing the type of plating used on the piece. Knowing what you are looking for can save you a great deal of time and money when buying and testing precious metals. Use a jewelers loupe to find the marking on the piece and consult the hallmark guide below to identify the purity. Take a look at our DETAILED TESTING GUIDE to translate your findings.
Used for testing precious metals with nitric acid for purity. To use the stone take the item in question and rub it back and forth against the testing stone leaving a strongly visible line of the metal on the stone. This is called a streak. If the item is suspected to be gold the streak should be a gold color and will feel slightly softer than most metals would when rubbing across the stone. If the streak left behind is copper colored or white the item is most likely not gold. With white gold the color of the streak may initially look white, due to rhodium plating that is applied to give it its white color, but the acid test will fade the white to a light gold color. If the item is suspected to be Silver or Platinum the streak left behind should have be white/silver color. Silver will also feel a little softer than most other metals when testing. Platinum is much more dense and will feel harder. You will get a feel of the metals the more you test. For items that may be heavily plated try to test deeper into the item by making multiple streaks from the same spot. The last streak should test just as well as the first. Always use a clean stone when testing. First rinse the stone under water to remove any leftover acid from prior testing. Use a piece of wet/dry ultrafine grit sandpaper to sand the wet stone clean. It is good to sand your stone when cleaning. The smoother the stone, the easier it is to get a smooth streak across your stone.
Acid Testing Solutions
These are used in testing precious metal purities. Gold will not be penetrated by nitric acid, so the test uses acids diluted to specific purities that correspond with how they will react with the metal in question. If an item is 14K gold it will stand up to the 14K acid test, but will be eaten away by the higher strength acids. Always wear gloves when testing with acids. The acid will burn your skin if exposed to it. If you do get acid on your skin, immediately run water on the affected area.
Rare Earth Magnet
The rare earth magnet is a quick way to weed out the pieces that are plated. If available, wave the magnet over the piece. Gold, Silver, and Platinum are non-magnetic. If the item is strongly attracted to the magnet it is not a precious metal. If only lightly attracted to the magnet, but hallmarked, it may be due to other alloys that are added to create purity. White gold is often attracted due to its magnetic rhodium plating. The magnet is used to save time and money on wasteful testing and should never be solely relied upon. Always further test all items that are not magnetic using the acid test.
This tool can be used when you suspect an item may be heavily plated. This test will damage the piece, especially if not gold. Take the needle file and file into an inconspicuous spot. Place the item down on the testing stone and place a drop of the corresponding acid directly to the spot you filed into. If the acid reacts to the piece by changing different colors and/or eating away at the item it is plated. If an item is real it will not have a reaction and will cause very little damage to the item. Clean, buff, and polish the item and the test will not be as noticeable.
Testing Gold & Platinum
After determining what to test for, place a single drop of the closest matching karat acid directly to the streak on the testing stone. If it is an odd karat item, use the closest lower strength acid. Wait 30 seconds and wipe away acid (the opposite direction of the streak) with a napkin. If the streak is still clearly visible the item is likely to be of at least that purity. If the streak is no longer visible the item is not gold or of a lesser purity. If the test was a positive result and you can visibly see the streak left behind, test the streak with the next higher level of acid. If the item is stamped with a purity hallmark the item should not be able to stand up to a higher strength acid and will disappear. If the streak does not disappear the item is most likely not gold. If there is no stamp on the item, you should immediately be suspect. If the item passes all of the prior testing, start with the 10K acid and work up in strengths until the streaks wipes away. The last visible streak is likely the purity of the item, but be extremely cautious when purchasing items that do not have a manufacturers purity hallmark. Using a needle file to cut into these items is usually necessary.
When testing for Silver you will use the 18K Gold testing acid. The acid will react to the silver in a different way than gold does. When testing silver be sure to get a very good streak on the stone. Place one drop of 18K solution on the streak and wait for the reaction. If the item is silver it will turn different shades of white-blue. Lower percentages of silver will give you a white/creamy color and higher percentages will be brighter blue. You may also use a silver testing acid which will change different colors for different purities. I find the 18K acid test to be more reliable, but use both when a piece is suspect.
Next Step: Determining Value
Now That You Know What You Have Make Sure To Check Out WHAT'S IT WORTH To Find The Value