How is a crackle glaze made?

Crazing is a crack pattern caused by thermal expansion mismatch between body and glaze. After the glaze solidifies (as the kiln cools) it shrinks more than the body. To relieve the tension of being stretched, it cracks. Crackle glazes are typically found on ware fired at low temperatures.

Can you glaze crackling?

Although crazing is considered a glaze defect, it can also be corrected by adjusting the clay body. A glaze adjustment might not be possible if it is under so much tension that there is no room in the recipe for correction.

What is crackle glaze called?

In ceramics, craquelure in ceramic glazes, where it is often a desired effect, is called "crackle"; it is a characteristic of Chinese Ge ware in particular. This is usually differentiated from crazing, which is a glaze defect in firing, or the result of aging or damage.

What is glaze crazing?

Crazing is one of the most common problems related to glaze defects. It appears in the glazed surface of fired ware as a network of fine hairline cracks. The initial cracks are thicker and spiral upward. These are filled in horizontally with finer cracks. Crazing is caused by the glaze being under too much tension.

What is the difference between cracking and crazing?

Craze cracks on concrete is when the surface of concrete develops a lot of fine cracks. Sometimes called map-cracking or alligator cracking, crazing of concrete is a result of conditions and curing methods at the point the concrete is laid or even the way it is finished.

All About Crackle Glazes

When was crackle glaze invented?

Since the 16th century, the Japanese have been creating beautiful and authentic raku pottery with a crackleglaze finish. The creation came from the tile maker Chōjirō who was instructed by Zen tea master, Sen Rikyū, to create pottery for his tea ceremony.

How do you make a crawling glaze?

Sometimes glazes are made to crawl intentionally. One technique to make this happen is to add 15-20% magnesium carbonate (testing required to determine amount) to a low fire transparent glaze.

What causes pottery glaze craze?

Crazing is due to a thermal expansion mismatch between body and glaze. As a piece of ware is heated and cooled during normal use, it expands and contracts. An incompatible clay and glaze usually means the glaze either immediately or eventually fails by crazing or shivering (the former being more common).

Does crazing devalue China?

While not everyone appreciates these cracks from an aesthetic perspective, crazing does not impact the utility of the underlying piece of china/ceramic/porcelain/pottery. Rather, it means there are teeny tiny surface-level cracks in the fired glaze of the piece.

What does ceramic crazing look like?

Have you ever seen a piece of pottery where the surface looks like it's covered with a spider web of tiny cracks? That's called crazing. They are not cracks in the actual piece of pottery but rather surface-level cracks in the fired glazed of the piece.

What is ceramic crazing?

Crazing refers to the formation of a network of fine cracks on the surface of glazed ceramics caused by tension between the ceramic body and the glaze. This process can come about in a number of ways.

What makes a glaze crawl?

Crawling. Crawling is caused by a high index of surface tension in the melting glaze. It is triggered by adhesion problems, often caused by bad application. It occurs where a glaze is excessively powdery and does not fully adhere to the surface of the clay.

What is shivering in glaze?

In shivering the fired glaze is under too much compression and begins to buckle or flake off in sheets exposing the underlying clay body. If one glaze shivers adjusting the glaze with a high expansion material such as frit or feldspar will bring the glaze into a compatible fit with the clay body.

Can crazing be repaired?

The crackling itself, also known as crazing, isn't something you can fix. When you run your hand over crazing, it should be relatively smooth. Any actual cracks or chips are considered damage and should be professionally repaired. To fade or remove brown stains within crazing, try this.

Why do old paintings look cracked?

Craquelure. Sometimes older oil paintings have a surface with a fine pattern of hairline cracks. These are known as 'craquelure' and have been caused by the ageing process of the paint. This is due to an old style of canvas and depending on the style and era of the artwork can appear in different patterns.

What glaze is used on porcelain?

What is a Mid Range Glaze? The mid-range or mid-fire glaze is used on porcelain and stoneware clay. Stoneware is the most common mid-fire clay, but you do see it used for porcelain more and more. The mid-fire glaze temperatures range from 2167 degrees Fahrenheit (1186 C) to 2262 degrees Fahrenheit (1239 C).

Are crazed dishes safe to use?

Generally, crazing is considered a glaze defect because the vessel can be significantly weaker than an uncrazed pot. Craze lines can also harbor bacteria or germs. Therefore, dinnerware pottery should be uncrazed ware.

What are cracks in china called?

Crazing is a term used to reference fine cracks that can be found in the glaze of pottery or china. Crazing can be present in varying degrees. Sometimes items may have a couple of crazing lines on one side and not the other, other times the crazing can look like a spider web and cover the entire item.

Can cold temperatures cause crazing?

It is upon the cooling of the kiln and the contraction of the wares that cracks form. Heating and then cooling too rapidly can cause the glaze to shrink too quickly and cracks appear more readily.