Gold Testing: How to Tell What Karat Your Gold Is
Ways to Determine the Karat of Gold
1. Look at the color
The deeper the orange-yellow color, the higher the karat.
2. Check the hallmark
Are the assay marks clear and are they from a country that you can trust?
3. Carry out an assay test
Take care. Wear protective clothing as you will be handling acid.
Karat Is a Measure of the Purity and Value of Gold
The value of gold is determined by its fineness or karat rating. An object made from 18-karat gold will cost you more than the same object made from 9-karat gold. An experienced jeweler will often be able to guess the value of an item just by looking at it, but they also carry out tests to determine the karat rating of gold. Knowing how a jeweler determines the karat value will help you, should you ever be buying or selling gold.
Karat (spelled "carat" in the UK) is a measure of the fineness and quality of gold. That is, the amount of gold relative to other metals that make up an object. In US and Canada, the most frequently used karat values are 14 karat and 18 karat (meaning 58.5% and 75% gold respectively). In UK, 9, 18 and 24 carat gold are the most frequently used alloys.
The higher the karat value, the greater the proportion of actual gold metal in your object. For example, an 18 karat gold ring will be made from 75% pure gold and 25% base metal (or alloy). A 9 karat gold ring will contain only 37.5% pure gold.
Assay Marks and Hallmarks
"Assay" means “a test." A gold assay test shows the percentage of gold in relation to other metals in an item. It is a test of value rather than of quality. Expensive materials can be poorly manufactured and, similarly, cheaper metals may have been worked with exquisite craftsmanship. An assay or hallmark is an objective chemical test. Deciding the quality of an object is subjective.
Hallmarks show that an assay test has been carried out on the gold object to confirm its karat rating. The reliability of the hallmark depends upon the country of origin. State-controlled assay offices imprint a mark onto the gold showing the year and place of assay together with the percentage of gold found, or the karat rating. The hallmark is very small so you may need a magnifying glass or jeweler's loupe to see it clearly.
If the hallmark is clear and easily readable, this is the quickest way to check the gold content of an item. However, over time some of these marks can become worn, and some may have been deliberately tampered with. So how do dealers determine how much a gold item is worth if the karat mark is indistinct or missing? There are several ways to do this, as explained below.
Test the Karat of Your Gold at Home
The only way to determine for sure an object’s karat value is to carry out an assay test. All jewelers and gold dealers will use an assay test kit before they purchase a gold item.
The kit consists of a number of different solutions of dilute acid and a touchstone. The touchstone is made of a dark acid-resistant rock such as slate. The jeweler rubs the gold object gently across the stone so that it leaves a streak mark. He or she then applies the acid solutions in turn to the mark. The higher the gold content of the metal, the less of it will vanish when acid is applied.
These chemical kits can be bought on-line for home use if you want to check the karat of your own gold items. I use the with scratch stone. The kit consists of six small bottles of acid (one for each type of metal to be tested), a scraper tool and a testing stone. The video below shows how simple the test is to carry out. Puritest Acid Gold Jewelry Test Kit
How to Test Gold Karat Using Assay Chemicals and Touchstone
Differences Between Fake and Real Gold
Real Gold Item
Fake Gold Item
Should clearly show the year and location of the assay test center. Consult reference books to confirm that you have a genuine hallmark.
Hallmark may be illegible or missing.
Gold is heavy. You can feel the weight of it in your hand.
Be suspicious if the object is lightweight. Gold-plated items may fool you by looking like solid gold until you judge their weight.
Compare prices before buying so that you have a good idea of the correct market value.
Remember the old adage. "If the price sounds too good to be true, then it probably is."
Pure gold is a very soft metal and will dent easily.
A gold-plated item will be harder because the gold is just a thin coating over a tougher base metal.
Gold does not react with nitric acid.
A lesser metal will foam or dissolve when a drop of nitric acid is applied.
How to Tell if Gold is Real or Fake
If you don’t want to do the acid test described above there are other ways to tell if your gold is real. However, they are not as easy to do and may not give such a clear result. The video below describes a few of them.
Indicators that show whether your coin or jewelry is pure gold or fake.
- Its weight will show if it has been adulterated with a lesser metal.
- Pure gold or silver has a distinct acoustic signature. This can be tested using an app or by using a special acoustic verifying machine.
- A magnet will reveal if there is any iron present in the metal. Gold is not attracted to a magnet.
4 Easy Tests to Spot Fake Gold or Silver
How Do Jewelers Test Gold and Why Do You Often Only Get Scrap Value?
Jewelers are shrewd business people. The value of gold fluctuates from day to day. Their ability to accurately assess the value of gold items is essential for them to turn a profit. Their offer to you will be related to the price they can achieve when selling on the item. They use science (objective) and experience (subjective) to test gold.
- They will examine your gold trinket using a loupe magnifying glass. They will check the authenticity of the hallmark and feel the weight of the item.
- Using acid and a touchstone, they will check the karat value of the metal. The chemical reaction of nitric acid on gold demonstrates the alloy content of the object.
- If the jeweler is satisfied with the result thus far, he will look at the quality of workmanship and the integrity of the item. If it is badly damaged, or of poor (tourist) quality, you are unlikely to be offered any more than scrap value.
Bars of gold are an investment vehicle by themselves and turning them into jewelry often does not increase its commercial value. The resale value of secondhand gold jewelry depends on supply and demand and there may be little demand for old-fashioned or dated pieces. Unless an item is individually crafted and of exquisite quality, second-hand values are low as the jeweler will simply be selling them on to be melted down into gold ingots for investors.
Gold Is Inert
- One of the reasons why gold is such a prized metal is that it is chemically inert. This means it does not react with air. Gold does not oxidize (i.e. rust) like many other metals.
- Gold also does not cause skin irritation if worn as jewelry. Discoloration or rashes on the skin next to the jewelry indicate that the gold has been adulterated with a base metal.
Can Vinegar be Used To Test Gold?
Vinegar (ascetic acid) can be used to clean some metals. It is not really a testing fluid, it is more of a cleaning agent. If you rub an object made of pure gold with neat vinegar it will remove marks and leave your jewelry shiny and clean. However, if the metal is not real gold, the acid will cause pitting (small holes) on the surface and your ring or bracelet will be damaged.
- Pour some white vinegar into a glass container. Do not dilute with water.
- Place your gold item into the liquid and leave for 15 minutes.
- Remove your gold pieces and rinse well in clean water.
Gold Varies in Color From White to Red
There are many variations in the color of gold, ranging from white through to deepest red. Pure gold is a deep golden yellow orange. In its purest state it is very soft and although this makes it very easy to work with, for everyday use a harder metal is needed. Pure gold is therefore combined with a cheaper base metal to form an alloy.
Copper or silver are commonly used in combination with gold to strengthen it. Thus what is commonly referred to as white gold has a high proportion of silver in the alloy. Similarly red gold contains a lot of copper in the alloy.