A ring for life together. Why MITUBACI chooses only "K18 (18K gold)"

When visiting jewelry shops and accessory stores, you increasingly see displays such as "K18," "K10," and "K5." We receive more and more questions from customers shopping for gold jewelry, such as "They all look like the same gold color, but what's the difference?" and "K10 and K5 are more affordable, but should I choose K18 or one of these?"

All gold jewelry created at MITUBACI is made exclusively from "K18 (18-karat gold)". We do not handle lower purity golds such as K10 or K5.

This is not simply because it is an expensive material, but because as a handmade ring workshop and jewelry brand that walks alongside our customers throughout their long lives, we have important commitments that we cannot compromise on.

This time, we will provide a detailed and careful explanation from the basic knowledge of gold as a material, to the reasons why MITUBACI continues to focus exclusively on K18, and the points for enjoying your rings as lifetime pieces for many years to come.

What is "K (Karat)" in the first place? Basic knowledge of gold purity

The "K" in the notation of gold jewelry stands for "Karat," which represents the "purity of gold" - indicating what percentage of gold is contained within the product.

It is a different unit from the "Carat" used to express the weight of diamonds and other gemstones. Gold purity is expressed on a scale of 24 parts, which is the worldwide standard. In other words, pure gold with 100% purity is expressed as "K24".

Using this as a standard, calculating the percentage of gold contained in the main types of gold yields the following:

・K24 (24-karat gold): Gold content 100% (pure gold)

・K18 (18-karat gold): Gold content 75% (18/24)

・K10 (10-karat gold): Gold content approximately 41.7% (10/24)

・K5 (5-karat gold): Gold content approximately 20.8% (5/24)

When arranged in numbers like this, you can see there is a significant difference. K18 is made up of three-quarters (75%) pure gold, but with K10 and K5, metals other than gold account for more than half of the total composition.

The non-gold portion is made up of a mixture of metals such as copper, silver, and palladium. These are called alloy metals (warigane). K10 and K5 have the advantage of being able to lower the price by reducing the proportion of gold, but at the same time they have the characteristic that the properties of metals other than gold become more pronounced.

Four reasons why MITUBACI continues to focus exclusively on "K18"

The reason we do not handle K10 or K5 and create only with K18 stems from our "responsibility to our customers' futures" gained through years of jewelry creation and maintenance experience. We will explain the four specific reasons.

1. Because it is unlikely to cause allergies and can be worn every day with peace of mind

Gold (yellow metal) is a metal with extremely stable properties. It is unlikely to deteriorate when exposed to sweat or air, and is a representative precious metal that is unlikely to cause metal allergies.

However, when the proportion of alloy metals (copper, nickel, etc.) increases as with K10 and K5, the metal components are more likely to dissolve when reacting with sweat and sebum, increasing the risk of skin trouble and metal allergies.

Wedding rings and special rings handmade at the workshop touch the skin every day for many years - for decades. Considering those with sensitive skin or potential changes in skin in the future, we choose K18 with high gold purity to ensure everyone can wear our pieces with confidence.

2. Because it resists discoloration and maintains beautiful luster with depth even as time passes

Pure gold does not discolor, but alloy metals such as copper and silver oxidize and discolor when reacting with oxygen, sulfur, sweat, and moisture in the air.

K10 and K5, having more alloy metals, may gradually become darkened or turn reddish as they are stored long-term or worn daily. In contrast, K18, being 75% pure gold, is highly resistant to discoloration and maintains the beautiful golden shine characteristic of gold for many years to come.

The major appeal of K18 is that you can enjoy unchanged beauty not just in the immediate term, but 5 years from now, 10 years from now, and beyond.

3. Because it has the durability for craftsmen to beautifully repair it repeatedly

MITUBACI is a workshop where our customers can handcraft their own rings. The one-of-a-kind ring created with care grows in sentimental value as you walk through life with it.

However, over the course of a long life, body shape changes, children grow, and finger size may vary with the seasons. In such cases, aftercare services such as ring resizing and re-polishing become necessary.

K10 and K5, which contain a high proportion of alloy metals, have properties that make the metal itself very hard and brittle. Therefore, when resizing a ring by cutting, expanding, or shrinking it, there is a high risk of cracks forming in the metal or welding marks becoming visible.

On the other hand, K18 combines appropriate strength with malleability (ductility).

Through the skilled hands of professional artisans specializing in metal engraving, resizing and re-polishing can be performed beautifully even after many years. K18 is an essential material to continue maintaining your handmade, treasured ring in perfect condition decades into the future.

4. It has "reliable asset value" that transcends time and never loses its worth

Gold is a metal with universal value recognized worldwide. Despite recent global circumstances and economic changes, the asset value of gold continues to be highly appreciated.

K18 is firmly recognized internationally as a "high-quality precious metal," and owning it itself holds certain value. When passing rings down to your children or future generations in the future, an 18-karat gold ring can be proudly passed on as a valuable treasure.

The charm of K18 colored gold available at MITUBACI

When you hear "18-karat gold," many people may think of dazzling yellow gold, but by adjusting the alloy composition ratio, we can create various beautiful color variations.

At MITUBACI, while maintaining the superior quality of K18 throughout, we offer a diverse palette of colors that suit our customers' preferences and skin tones.

・K18 Yellow Gold: A golden hue with classic brilliance and elegance.

・K18 Pink Gold: A warm-toned color with good skin compatibility that imparts a soft and gentle impression.

・K18 White Gold: Often called blue gold, this is a gold with a brilliant impression.

・K18 Champagne Gold: A natural color that seamlessly blends with the skin, with an exquisite balance of yellow and silver tones.

Whichever color you choose, all contain 75% pure gold in 18-karat quality, so the depth of color and smoothness of touch are truly exceptional. At our workshop, you can handle actual sample rings and experience the difference in color and texture when placed against your skin.

The "tactile sensation of genuine materials" that can only be felt through hands-on creation

At MITUBACI's workshop, you can experience the creation process where you yourself use a hammer to tap the ring, stamp engravings, and carefully polish the surface.

During this creation process, the difference in materials is clearly evident in the "tactile feedback" when striking the metal and the "beauty of the hammer marks."

K18 provides a uniquely pleasant tactile sensation when struck with a hammer—neither too hard nor too soft. As you tap it, the metal's density increases, making the ring more resistant to scratches and stronger. The time spent using craftsman's tools with your own strength to impart patterns and form to authentic K18 gold is a luxurious and special experience found nowhere else.

A ring you have created from scratch with your own hands generates far more attachment than purchasing a ready-made product. That is precisely why we want to provide you with the finest K18, a material worthy of a lifetime of love.

Tips from our craftsmen! Daily care for K18 rings and frequently asked questions

We introduce frequently asked questions from our customers and simple daily care methods you can do at home.

By having the correct knowledge, you can keep your K18 ring beautiful and pristine for much longer.

Q1. How should I care for my ring on a daily basis?

After wearing, the basic step is to gently wipe away sweat and oils using a soft cloth or eyeglass cleaning cloth. If you notice oils or tarnish, dissolve a small amount of neutral detergent (such as dish soap) in lukewarm water and gently wash with a soft brush (such as a toothbrush), and the brilliance will be restored as if it were new. After rinsing, make sure to wipe away moisture thoroughly with a soft cloth.

Q2. Should I remove it when taking hot spring baths or swimming in the ocean?

K18 is a material that resists discoloration, so it is generally safe to wear in hot springs. In rare cases, components contained in hot spring water—particularly sulfur—or salt contained in seawater, or chlorine used in pools may cause a slight discoloration of the surface. Even if discoloration does occur, the color can be restored by polishing the surface, so please rest assured.

Q3. What should I do if my ring gets scratched in daily life?

When worn every day, fine scratches inevitably accumulate from daily life. However, these scratches are also evidence of the time you've spent together as a couple, and they give the ring character and depth. If you ever wish to "return it to its sparkling original state," please rest assured. MITUBACI offers after-sales polishing and finishing services by skilled craftsmen. With K18, you can restore it to a beautiful, like-new brilliance no matter how many times it is polished and refinished.

Summary: A Compromise-Free Choice as a Gift to Your Future Selves

When selecting jewelry, price and design are certainly important factors. However, because handmade rings are something you will continue to wear as "lifelong memories," we do not want to compromise on material quality, durability, and future maintenance.

The "gentleness on the skin," "resistance to discoloration," "ease of resizing," and "timeless value" that only K18 offers—qualities not found in lower-purity K10 or K5. All of these lead to customer satisfaction and peace of mind years and decades from now.

"I'm so glad we chose this material." "Even now, after 10 years, it remains as beautiful as ever." So that our customers can say these things, MITUBACI will continue to insist on K18, the finest material, and will continue to help create rings with care and dedication.

At MITUBACI's workshop, you can actually hold K18 sample rings in your hands and confirm their substantial weight and deep, radiant brilliance. If you have any questions or concerns, please feel free to reach out to our staff or craftsmen at any time.