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 a crazed glaze?

Crazing is a glaze defect of glazed pottery. Characterised as a spider web pattern of cracks penetrating the glaze, it is caused by tensile stresses greater than the glaze is able to withstand.

Are dishes with crazing 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.

How do you fix a crazing glaze?

If you do want crazing to happen, try lowering the firing temperature. Avoid adding extra silica or sand to the clay body. Conversely, ways to correct crazing include changing to a different clay body which better fits the glaze, adding silica to the existing clay body or increasing the firing temperature.

Is crazing bad on pottery?

Technically crazing is considered a defect in the glaze and can weaken the item. It may also harbor bacteria. So if you are buying pieces to use for serving food you should look for uncrazed pieces.

Crazing (food safety in glaze)

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.

How do I stop crazing in pottery?

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.

Does crazing reduce value?

The presence of crazing usually diminishes the value of objects but it can depend on the severity of the damage and rarity of the crazed piece.

How do I know if my glaze has lead in it?

If the decorations are rough or raised, if you can feel the decoration when you rub your finger over the dish, or if you can see brush strokes above the glazed surface, the decoration is probably on top of the glaze. If the decoration has begun to wear away, there may be an even greater lead hazard.

How do you remove crazing from dishes?

Use Oxygen Bleach

Mix in the powder with hot water and stir thoroughly. Allow it to cool, and then place the dishes in the mixture and let them soak for a few hours. Check on the dishes after two hours to see if there is any progress. The stains should start to fade away.

Does crazing get worse?

Crazing can happen at the time of firing but it can also come about years after a piece is produced. It is important to take good care of your pieces to prevent this from happening when possible. Crazing also weakens the piece as the protective layer leaves the body of the piece more vulnerable.

What causes glaze to craze?

Crazing is caused by the glaze being under too much tension. This tension occurs when the glaze contracts more than the body during cooling. Because glazes are a very thin coating, most will pull apart ar craze under very little tension.

What does crazing mean?

1 : to make insane or as if insane crazed by pain and fear crazed addicts. 2 : to produce minute cracks on the surface or glaze of crazed glass crazed pottery. 3 obsolete : break, shatter. intransitive verb.

What makes a glaze crackle?

The “crackle pattern” in the glaze is actually a firing defect called “crazing.” Simply put, crazing is occurs when the glaze shrinks more than the body. The tension of the glaze on the body causes the glaze to crack.

How do you check for crazing?

Crazing appears when ceramic is cooled and the glaze shrinks more than the clay to which it is rigidly attached. Shivering, on the other hand, usually first appears when ware is suddenly heated.

Why is my glaze cracking before firing?

When a glaze cracks as it dries on a pot, it usually means that the glaze is shrinking too much. This is normally caused by having too much plastic material (ball clay) in the glaze.

Is cracked glaze safe?

Glazed ware can be a safety hazard to end users because it may leach metals into food and drink, it could harbor bacteria and it could flake of in knife-edged pieces. Crazed ceramic glazes have a network of cracks.

Why is my clear glaze crazing?

Crazing is caused by the glaze being under too much tension. This tension occurs when the glaze contracts more than the clay body during cooling. Because glazes are a very thin coating, most will pull apart or craze under very little tension. Crazing can make a food safe glaze unsafe and ruin the look of the piece.

Why does old varnish crackle?

It is harder to see, but with oblique light you see numerous fine parallel cracks under the surface of the varnish. This is due to shrinking of the wood and happens most when improperly dried or relatively new wood is used.

Is crazing a crack?

Crazing in concrete is the development of a network of fine random cracks or fissures on the surface of concrete caused by shrinkage of the surface layer. These cracks are rarely more than 3mm deep, and are more noticeable on over floated or steel-troweled surfaces.

What does craze proof mean?

The term “craze proof” which meant that the piece would resist forming that unsightly crackle pattern of damage from temperature and humidity changes. This was used, rarely, after 1930.

Why is my ceramic mug cracking?

It's caused by a slightly poor "fit" between glaze and clay body of the ceramics, usually because of too much silica in the glaze. With some glazes, it's intentional; celedons craze, as do white raku glazes. What you're seeing there is unintentional crazing.

What does crawling mean in ceramics?

Crawling - A bare spot (from the shrinking of a glaze) on a finished piece where oil or grease prevents the glaze from adhering to pottery.