How do you check the purity of Yellow Gold or K Gold? Explain the detection, calculation and judgment method of gold purity in detail! | JEWEL CAFÉ Malaysia

Date published: September 14, 2020

How do you check the purity of Yellow Gold or K Gold? Explain the detection, calculation and judgment method of gold purity in detail! | JEWEL CAFÉ Malaysia

Gold has been loved all over the world as jewelry and assets since ancient times. However, apart from being a well-known material, few people understand the difference in the meaning and purity of engraving.

The Value of Gold Depends on “PURITY”.

We will introduce information about the “purity” that determines the gold price standard from different angles, and “how to check the purity of gold by yourself” for your reference.

What is the meaning of “K” in “Koo” ? About Gold Unit and Indications

Have you ever seen the “K24” or “K18” engraving as a gold mark on gold products? The “K” in “K○○” refers to the abbreviation of “karat”, and the so-called “K○○” symbol indicates the “gold purity” used in the product.

What is “GOLD PURITY”

“Gold purity” refers to the gold content. That is to say, “what percentage of gold (pure gold) is contained in the product”. In fact, many gold products are not made of “only pure gold”. If it is made of “only pure gold”, it is made of “pure gold”, but jewelry and other gold ornaments are mostly made of pure gold and other metals.

The purity of gold is indicated at a rate of 24 points

Japan uses a 24-point rate to indicate the purity of gold. In other words, 100% pure gold (pure gold) = K24 (24 gold). (Actually, in Japan, 99.99% or higher purity gold is labeled K24.) Every time K1 is increased, the pure gold content will increase by 4.17%. If it is K18, the pure gold content will reach 75%.

Note 1 – The difference between “K Gold (karat)” and “Carat”

The spelling of “karat” and “carat” used for gems are different, and they are completely different units. The “karat” of gold means “purity”; the “carat” of gems means “weight”. It is said that when the purity of gold is expressed in Japanese, it will be marked as “18 gold” to avoid confusion with the “carat” used for gems.

Note 2 – About “24 points rate” and “1000 points rate”

Why use “24 points” to represent gold purity? There are different opinions on this point. It’s said that because the locust bean has 24 equal parts, the 24 equal parts were used as the unit of gold trading in the early days, and it was determined as the unit of pure gold. Another said is that there are 24 hours a day, and using the 24-point rate as a general unit, this unit continues to this day. After humans began to come into contact with gold, the concept of so-called 100 points began to appear. Also because of the emergence of the 100-point rate, just like the popular platinum and silver “Pt900” and “Silver925”, the more precise 1000-point rate is used to indicate the 100-point rate. If 1000 points are used to mark gold, K24 is marked as 999.9. This method is most commonly used for ingots (gold bars, bullions).

The intention of mixing gold with other metals

The higher the purity, the more valuable and beautiful appearance. But why do jewelry use alloys blended with other metals? In fact, pure gold has the disadvantages of soft texture, heat resistance, deformation and damage. But on the other hand, because it has the characteristics of being easy to blend with other metals, it can be made into a mixed alloy. It’s to make up for the shortcomings of pure gold. Furthermore, it also has the advantage of changing the type and proportion of the blended metal to make the color of rose gold and platinum different. Here we will introduce the mixing ratios of pure gold and mixtures of gold (YG), rose gold (PG), and platinum (WG), which are most commonly found in jewelry, for reference.

YG | when it’s K18 | (75.00: 15.00: 10.00%)
PG | when it’s K18 | (75.00: 10.00: 15.00%)
WG | when it’s K14 | (58.33: 41.67: 0.00%)

*The numbers in ( ) indicate the ratio of pure gold: pure silver: pure copper
*It is only a general value, the correct ratio will vary depending on the product

Incidentally, platinum, which is often confused with platinum, is an alloy of pure gold mixed with silver, nickel, and palladium. In fact, the two are completely different.

Will it vary by purity? Uses and characteristics

Most of the gold products circulating in the market are one of five types: K24, K22, K18, K14, and K10. The following will introduce the pure gold content ratio, characteristics and uses.

K24 ・ 24 GOLD ( PURE GOLD 99.99% ~100%)

It will not decay or change color because the pure gold content is nearly 100%, and it can maintain its luster forever. However, due to its soft texture, it is not suitable for jewelry, and is mainly processed into products with asset value such as gold bar/ bullions or coins. The gold leaf with the impression of pure gold is usually K23 containing 4.90% pure silver and 0.66% pure copper.

K22 ・ 22 GOLD ( PURE GOLD 91.7% : MIXTURE 8.3% )

Usually this kind of purity is rarely heard, but in recent years it has begun to attract attention, and its main use is to make jewelry. Although it is harder than K24, it still has the characteristics of softness and easy damage due to its high gold content, so be careful when using it. In Asian countries outside of Japan, they preferred dark golden, so K22 jewelry with close to pure gold tone and brightness seems to be quite popular.

K18 ・ 18 GOLD ( PURE GOLD 75% : MIXTURE 25% )

While maintaining high purity, K18, which has easy processing softness and appropriate hardness, is very suitable for jewelry. Even the color variations of rose gold and platinum are extremely attractive. In addition to jewelry, it is also used for a wide range of purposes such as watches, lighters, cameras, and smart phone cases.

K14・ 14 GOLD ( PURE GOLD 58.5% : MIXTURE 41.5% )

Although the advantage of increased durability is that it can be increased through the proportion of the mixture, on the other hand, as the pure gold content decreases, the gloss will deteriorate and the risk of discoloration will increase. However, the reduced content of gold and its relatively low price have created its charm, so it is processed into many products such as jewelry and pens and is widely circulated.

K10・ 10 GOLD ( PURE GOLD 42% : MIXTURE 58% )

K10 has been launched in recent years due to affected by the high price of gold. The proportion of the mixture is higher than gold, so the brightness is not as good as the above-mentioned purity products, and there is a tendency to rust. But it is easy to process and cheap, so it appears in large numbers on the market. Most of them are processed into jewelry. As the purity of gold decreases, the risk of people with sensitive skin becoming allergic to metal products will increase. If you are worried about allergies, it is best to choose products of K18 or higher when buying jewelry products.

An easy way to check the purity of gold yourself

Is there any way to check the purity of gold? If you are an industry operator, you can use professional X-ray analyzers for identification. However, the cost is expensive, and it is not easy for individuals to buy. Therefore, the most appropriate way is to entrust an expert to appraise. In addition, the following will introduce three simple methods that individuals can also measure the purity of gold for reference. Whether you want to actually try it or read it based on knowledge or curiosity, please make good use of this opportunity to learn about the identification method of gold purity.

STEP 1, Confirm the Weight & Texture – Firstly, Understand about the nature of gold

This method is not used to investigate purity, but to investigate “fake or real gold”. First, I want to introduce how to understand the nature of gold.
Check Method
Based on the characteristics of “gold being heavy, easy to heat and cold”, the judgment can be made only by the touch of the hand. The characteristic of high-purity gold products is that they are heavier and heavier than the size of their appearance. In addition, there is a cold feeling at the moment of touching, but due to the high thermal conductivity, it will be warmed by body temperature immediately.

Disadvantages
• It takes experience to develop these feelings
• High-precision fake gold cannot be judged by this method

STEP 2, Submerged in water to measure specific gravity-an ancient method before the era

There is also a method to check the purity of gold from the specific gravity by using the characteristic of “heavy gold”. This is a popular method used in the time of Archimedes before the Era. Specific gravity means that when the weight of water is 1, use the same volume (1cm3) as the object to express the weight. When water is 1, the specific gravity of K24 pure gold is 19.13-19.51 (approximately 20 times that of water); K18 is 14.84-16.12 (approximately 15 times that of water), which shows how heavy the weight of gold is. So, how is the specific gravity measured? Although it can be easily measured with a professional hydrometer, the price of a hydrometer is more than 100,000 yen, so I will explain how to easily measure specific gravity using a kitchen scale that can be purchased for thousands of yen. (Please use 0.1 gram as the unit of measurement, with the “zero function” that can deduct the weight of the container). Here will be an example of gold products engraved with K18.

Check Method
1. Firstly, Measure the weight of the gold product under inspection (assume this value as A).
2. Next, place the container with water (a lighter weight container is preferred) on the electronic scale and use the “zero-return function” to display zero.
3. Put the gold product to be inspected into the water and measure the value (assuming this value as B). Water is 1cm3=1g, so the value of B becomes the volume of gold products.
4. B÷A=The proportion of the inspection object (assume this value as C).
The specific gravity of K18 is 14.84-16.12. As long as the C value is within this range, the possibility of belonging to K18 as indicated by the engraving is quite high.

This method should pay attention to is that at the aforementioned point 3, the gold product as the measurement object needs to be completely immersed in water and in a suspended state. In addition to not being exposed to the surface of the water, it is also not allowed to lean against the bottom and sides of the container. Therefore, if it is a ring, hung it with wire, if it is a necklace, a net must be prepared. At this time, whether it is a container or equipment that has been filled with water, it must be zeroed and displayed as zero in the in-position state. But this method also has disadvantages.

Disadvantages
• It is impossible to measure products with special shapes such as a hollow center and no room for water intake, and design products with jewelry.
• When using fake gold made of metal whose specific gravity is close to gold, such as “tungsten”, the measured value is almost the same as real gold.

STEP 3, Investigate using touchstones-an identification method passed down from the Edo period

The last thing I want to introduce is the method of using the touchstone, which has been used since the Edo period, and a very historical method of identification is to use the black slate of the so-called “Nachi Black Stone” as the touchstone.
Check Method
Rub the inspected gold product on the touchstone, and then observe the color, depth and residual condition of the scraped gold left on the stone surface to determine the purity. If it is pure gold, it will show a strong orange color, forming a deep dark color close to bright yellow, but the orange will fade into a bright hue as the purity decreases. When it drops from K14 to K10 or so, the copper content will be greatly increased and the color will become darker. However, it is difficult to judge by color, unless you have accumulated a lot of experience. As a comparison object, it is recommended to choose a “test gold bar” that confirms the golden hue according to purity for reference. A small touchstone can be bought for only a few thousand yen, and those who are interested can challenge it.

Disadvantages
• It is a destructive inspection, which will scratch the surface and sometimes damage the inspection object due to cutting.
• Novices can’t easily distinguish color by purity.

Conclusion

The value of gold depends on “purity”. Those who consider gold as an asset or buy gold jewelry, if they can really understand the purity knowledge, will be helpful when buying.

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