Knowing how to test gold on your own is a must when it comes to buying jewelry and bullion. In a world where a missing gram can cost thousands of dollars, there is no one you can trust better than yourself. Testing gold at home can seem like a complicated process, but we’ll walk you through how to do it safely in this guide.
Forgers, Forgers Everywhere!
Even if you see a visible purity mark on your gold bar, you can’t always be sure of its true gold content. Many products have an inflated fineness mark. Moreover, the market is saturated with gold-plated jewelry hiding metals of lesser value underneath.
To know the value of your investment, you first need to appraise it accurately. There are many ways to do this without the help of a professional, although it’s a good idea to do it with supervision the first few times. Here are some of the things to look out for when appraising gold.
Know Real Gold
Gold is a metal that’s resistant to most corrosive elements, like rust and moisture. You can bury it underground, keep it in zero gravity, or hide it in the ocean, and it will retain its original form for thousands of years.
- Gold doesn’t rust like any other metal because it’s resistant to the effects of oxygen.
- Gold has little to no magnetic properties, so while it’s technically magnetic, it will not stick to fridges or stronger magnets in the manner of cobalt, nickel, and iron.
- Gold is a great conductor of heat and electricity, which is why it’s priceless in the field of circuits and electronics.
- Gold is only capable of dissolving in a mixture of 25% hydrochloric acid and 75% nitric acid, otherwise known as nitrohydrochloric acid or aqua regia.
- Gold is soft and malleable, so it must be fused with some percentage of silver, platinum, copper, or nickel to attain rigidity.
Measurements to Keep in Mind
Gold is sectile, which means it can be cut into pieces and molded into shape with tools you can find in a hardware store. The purity of sectile metals is measured by karats, and one karat is equal to 1/24 parts of gold in a metal fusion, also called an alloy. When gold is designated as 24-karat, that means 24 out of 24 parts of the material is gold, making it 100% pure.
The millesimal fineness system breaks this down more accurately, as it indicates the exact percentage of gold in an alloy. For example, in a 21-karat gold bar, 21 out of 24 parts are made of actual gold, while the remaining three parts come from other metals. That makes it an 875 in the millesimal system because it’s 87.5% gold and the highest you can attain is 999 or 99.99% purity.
That’s everything you need to know about gold properties and measurements. You’re now ready to venture into the different testing methods you can do at home.
How to Put Gold to the Test
The Magnifying Glass Method
This test only requires jewelry or bullion and a magnifying glass. Look through the lens carefully to inspect the visual quality of your gold. Here are some things to spot:
- Unless subjected to specific processes, your gold should never be discolored. Discoloration only occurs with a low concentration of gold in an alloy, because silver, copper, and other metals are reactive to oxidation.
- Unlike the gold we see in movies, gold bars are not that shiny, and in fact, have an almost soft matte yellow finish. If your bullion is too vibrant or has some visible discoloration, it may not be pure, especially when you detect a reddish hue.
- Most gold items have a purity mark that indicates actual gold content by karat or millesimal fineness. These markings can easily be faked, so you should never rely on them alone. They are, however, very useful for finding gold below 10 karats, which is not considered true gold by US standards.
The Stamp Test
Purity marks are mandated by law on all gold items, including jewelry. These stamps are a great way to know just how much gold you’re getting for a particular item.
These markings are found in different places on jewelry. For example, on bracelets and necklaces you should find a stamp around the clasp, and on wedding rings and championship rings the marks are found on the inner surface. These markings include the manufacturer of your gold jewelry and its purity in millesimal units or karats.
Here are a few grades you should avoid:
- GF means gold-filled jewelry, which has a small layer of gold bonded to some base metal. An item only requires 5% of its weight in gold to be categorized as gold-filled.
- GP means gold-plated jewelry, in which a thin layer of gold has been electronically applied to the exterior of a base metal. These items can be marked HGP for hard gold plating or SGP for soft gold plating. An HGE or GEP mark is essentially the same, designating hydrostatic gold electroplating and gold electroplating, respectively.
- A grade of .925 is mostly reserved for sterling silver, and only a very small amount of the item in question will be made of gold.
The Scrape Test
Even though gold is pretty tough when alloyed with less precious metals, they can still be scratched with the right materials. The scrape test, also known as the scratch test, is mostly reserved for professionals because it can permanently change the value of your gold if performed incorrectly. Be sure to take extra caution.
You’ll need an unglazed porcelain tile/ceramic plate or a black jeweler’s stone, which you can purchase from a trusted jeweler. Slowly swipe the ceramic tile or jeweler’s stone on the surface of the gold with just enough force to leave a light dent. Look at the streak left behind.
A soft yellow color means you have genuine gold, while a dark, nearly black streak could signal that you have a piece of pyrite.
The Vinegar Test
A lot of metals and minerals react to vinegar’s acidity, and this is one of the easiest and most accurate tests you can perform on gold. All you need is some vinegar, a dropper, and the gold you’re testing.
Do this test in a place where no interior lighting can mess with your perception of color. Take a few drops of vinegar and place it on top of your bullion or jewelry. There should be no changes in the soft yellow color of your item.
After you’re done with the dropper test, soak your gold in a clear container filled with vinegar. Let it sit for about 15 minutes, then rinse it. Your jewelry should come out unchanged or slightly shinier; any discoloration would disprove its authenticity.
The Gold Acid Test
By far the most accurate and well-known test you can do at home, the gold acid test should be completely safe for jewelry and bullion that claims a high percentage of gold content. This is mostly reserved for non-decorative investments because some light scratching might occur on the gold’s surface.
To perform this test, you must first subject your item to a magnetism test, so you won’t cause any damage if it’s made of precious metals with a low concentration of gold. Get yourself a high-strength magnet from a hardware store and see if your gold piece is attracted to it. Gold has little to no magnetic charge since it’s a non-ferrous metal, so if it passes, you’re clear to go ahead with the gold acid test.
You will need:
- A paper towel, a clear piece of glass, protective eyewear, and rubber gloves.
- An acid kit that includes nitric and hydrochloric acid with droppers. Proportions may vary depending on the karat you’re testing.
- A black gold testing stone that’s rubbed with 320-grit sandpaper, then washed and rinsed.
- Two beakers: one filled with a water and baking soda solution and one with just water.
- Gold acid test needles with the correct gold tip for your item’s karat level.
This process tests your gold with increasing intensity until only pieces with the highest purity remain in the final stages. First, place your item on the paper towel, then create a small dent in an unseen spot that’s deep enough to see the metal underneath. Items with a high karat rating can be malleable, so you should have no trouble doing this.
Place a single drop of nitric acid onto the dent. If it starts to bubble and create a fizzing sound, this means it’s burning through whatever metal is mixed in with your gold or that your item may not be gold altogether. If it yields a cream-like substance, that means you have gold-plated silver, which is still fairly valuable.
If your item doesn’t pass the nitric test, no further testing is necessary. However, if you observe a rusty-looking spot forming inside the dent, you may still have gold, albeit of a lower karat number. Keep testing your item with different acids designed for different karats, starting from the highest.
Once you’ve found a testing kit that produces no discernible reaction to your item, you’ve found the right karat. Remember to wash off the karat acid with the water and baking soda solution before moving on to another concentration.
Find a Reputable Source for Quality Gold
Oxford Gold Group knows how to test gold, silver, and all manner of precious metals better than anyone can at home. Browse their catalog of gold products today for professionally tested bars and coins that make very wise investments. Call 833-600-GOLD (4653) for a trustworthy, reliable source of quality gold and other precious metals.