ZIRCONIA

Zirconia is a special material made from naturally occurring minerals. 

This page will explain some of its unique characteristics.

ジルコニアとは1
 

As Hard as a Gemstone

宝石の様な硬さ

People often wonder if zirconia is a metal.  Many are surprised to learn that it is actually a type of porcelain. 

 

Let’s go into a little more detail. 

 

Electricity is the movement of electrons.  An electric current flows through metal because of the motion of the electrons within the material.  The electrons are moving around because the metal is trying to let go of its electrons.  When these negatively charged electrons are released, the metal becomes positively charged and the metal atoms repel each other, much like magnets with the same poles facing one another.

 

The reason why metal atoms stick together is because the electrons that go around the atoms act like ropes and bind them together. This is called a metallic bond which is actually the weakest among all chemical bonds.  When another object hits the metal with enough force, the metal atoms can easily change position and transform the overall shape.  Since metal atoms are bound by the electrons rotating around them, even if the positions of the atoms were to change, the electrons would continue to rotate all around, and the overall structure would not fall apart.

 

On the other hand, porcelain and gems do not conduct electricity.  This is because their electrons are fixed.  For example, sapphire is made of aluminum and oxygen.  Positively charged aluminum atoms emit electrons, and negatively charged oxygen atoms receive these electrons.  Much like the S and N poles of magnets that come in contact with each other, aluminum and oxygen atoms become strongly linked. This is called an ionic bond. 

 

Porcelain, gemstones, etc. are in fact harder than metal because they carry bonds that are much stronger than metallic bonds.  This is also the case with zirconia, which is a type of porcelain made from combining a metal called zirconium with oxygen.

 

Suppleness of Metal

金属の様なしなやかさ

The relatively well-known transparent material that is used to make imitation diamond is actually called “cubic zirconia. The zirconia used at ZIKICO is a little different. In cubic zirconia, as the name implies, the shape of the crystal is cubic.  It is transparent because it is composed of only one type of crystal.

 

On the other hand, the zirconia used by ZIKICO (partially stabilized zirconia) is made by packing together two kinds of very small crystals.  Consequently, the light hitting the surface gets refracted in random directions making the material look white.

 

The average size of these tetragonal and monoclinic crystals is about 0.3 μm (about 1/100th of the thickness of a human hair).  However,  the volume, type, and size of the crystals can vary depending on the minerals added, their relative proportions, and the baking time. The utilization of the two types of crystals with different shapes allows zirconia to be as flexible as metal.

 

Non-allergenic like Porcelain

磁器の様なノンアレルゲン

As established earlier, the connection between metal atoms is weak because they want to give away electrons. When something pulls on the electrons from the outside, some metal atoms transfer electrons and become ionized. This causes those metal atoms to immediately break their bonds and escape.  When the ionized metal atoms come into contact with human protein, it can turn the protein into an allergen and cause an allergic reaction in some people.

 

Even if there is an oxide layer on the surface (as with stainless steel), the metal could become exposed if the layer is scraped by coming into contact with another object such as a plate. 

 

Conversely, porcelain is non-allergenic since the structure contains oxygen atoms that attract electrons, making the bonds stronger and more stable. Oxygen atoms have low ionization energy, so once they are bound, they will not react with other elements.

 

This is also true for zirconia, which is a type of porcelain made by combining a metal called zirconium with oxygen.

 

The Scientific Reason Why Food Is More Delicious with ZIKICO Cutlery

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Zirconia enables your taste buds to savor the full palette of subtleties of the cuisine for two main reasons:

 

 1.  Unlike conventional silverware which alters the flavor of certain dishes, zirconia does not alter the taste of the food.

 

It is said that there are five basic types of taste: sweetness, sourness, saltiness, bitterness, and umami. 

Unbeknownst to most, umami is actually the taste of amino acids. 

Amino acids are flavorless themselves, but they develop a certain taste when mixed with a small amount of metal ions.  Therefore, salt (which contains sodium, a type of metal) is added to enhance the umami of a dish.  The umami changes depending on the amount and quality of the salt.

According to the Umami Seasoning Association, a salt concentration of 0.4% to 0.8% is ideal in most dishes. 

 At ZIKICO we believe that it is important that food reaches everyone’s taste buds with the exact umami intended by the chef. 

 

2.  Zirconia itself is flavorless and does not impart a metallic odor to fine cuisine.

 

With conventional cutlery, that metallic odor you may experience is not actually the odor of the metal itself, but it is the organic matter in your mouth reacting with metal ions.

Metals tend to oxidize very easily. This is especially true for silver, copper, and iron (found in stainless steel).  The chemical reaction which causes that unpleasant metallic odor occurs when organic substances come into contact with oxidized metal ions.  So this means that fats and other elements contained in food as well as in your mouth can react and cause that metallic odor.

Since the atoms in zirconia are not ionized, they do not alter the flavor of food or react with organic matter to impart a metallic flavor.

Referrences
※1 (Umami Seasoning Association)

※2 (Science Daily)

 

The Color of Zirconia

ジルコニアの色

Since we make black and white colored cutlery, people often wonder what the original color of zirconia is. 

 

The original color is a slightly translucent white. Other colors are created by mixing in different minerals.

 

Usually, ruby is red and sapphire is blue, but these are both crystals made of the same mineral called alumina (corundum).  The color of alumina is originally white, but when combined with chrome, it turns red and makes ruby.  When combined with iron and titanium, it turns blue and makes sapphire. 

 

When combined with chromium, emerald and alexandrite change color to red or green, depending on the light. 

 

However, mixing in these same minerals does not always result in the same colors for zirconia.  For example, if you mix chromium with zirconia, it will not turn red, but will turn green. 

 

The colors of regular paints are made of organic pigments derived from plants or petroleum, and will eventually degrade.  Glaze used for ceramics and pigments in Japanese paintings are made from minerals and do not fade over time. 

 

Similarly, colorless gems such as diamonds never change color.  This is also the case for zirconia which is colored by minerals. 

 

Zirconia does not become discolored even when soaked for many years in acids, alkalis, detergents, bleach, oils, spices, etc.

 

In the unlikely event of yellowing, your zirconia cutlery can be easily cleaned with a melamine sponge.