This is likely the result of thermal shock. In this case the clay and glaze expand at different rates when exposed to temperature variation, and this change causes the object to crack. To be more specific, the body has contracts more than the glaze.
If the piece is old enough, the glaze may contain lead, which can leach due to the crazing. In that case, the piece should definitely be discarded. Technically, most health codes require crazed dishware to be discarded, although you can assess your tolerance for risk.
Cracking is mainly caused by uneven drying of the piece, meaning that some parts of the pottery shrink more than others.
What is crazing? Crazing is the effect on pottery which causes it to have a web of tiny cracks over its surface. These are not cracks in the actual structure of the pottery but actually an effect on the glazed part of the pottery.
First, put the piece on a flat surface, such as a tabletop. Then give it a little tap. “If it rings it's probably fine,” Lackey says. “If it's a dull sound, it means you'll want to look a lot closer.” That dull sound usually — although not always — will indicate a crack or defect.
Hard, dense, and solid, porcelain is resistant to most heavy stresses and can even be used in commercial environments. Be aware, though, that the hardness of porcelain can make it slightly more brittle than standard tiles, which means they can be more susceptible to cracking.
If you are joining broken pieces, opt for a strong liquid or gel adhesive that dries clear. Loctite Super Glue Gel Control quickly forms strong bonds with porous surfaces like porcelain and sets without clamping. It's a great choice for fixing broken porcelain. Super glues are super adhesives!
Cracking is easily identified by the observer visually and through physical touch. It's also easy to understand that the material has been weakened when cracks are present. Crazing: internal fracturing without a change of the surface texture.
Details. Crazing refers to small hairline cracks in glazed surfaces that usually appear after firing but can appear years later. It is caused by a mismatch in the thermal expansions of glaze and body.
Porcelain patching glazed and epoxies can run so it's best to protect the surrounding area. For a crack or a scratch, use the touch-up glaze to fill in the damage. In most cases, the bottle of glaze will have a paintbrush built into the cap. If not, use an artist's paintbrush to apply the touch-up glaze.
The standard strength test for porcelain dinnerware should yield an impact strength of about 0.36 foot-pounds of force. The flexural strength for these materials is about 60-70 megapascals (MPa), about 8700-10,200 pounds per square inch (psi), at best, with earlier examples being significantly weaker.
Pouring boiling water is quite risky as it might lead to a steam burn or scalding. Another thing to keep in mind is what type of material you are pouring in into. If you have a porcelain sink, it is likely to crack due to the heat. All in all, pouring boiling water down your drain will only cause issues down the road.
Porcelain is less likely to crack under extreme heat, whereas ceramic can become damaged, cracked, or even change shape when exposed to extreme heat.
Not everyone likes the antiqued look—even antique dealers find it frustrating, as it significantly diminishes the value of the piece. Crazing in china is a sign of instability in the glaze, which can make the china more delicate and susceptible to damage over time.
Technically, crazing is considered a defect in the glaze and can weaken the item. It may also harbor bacteria.
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.
Cracks between 5mm and 15mm wide are more likely to be serious and may need professional repairs. Any crack bigger than 25mm wide should definitely be examined by a professional. If the crack is wider at the top than the bottom, and visible on both the outside and inside of your home, you might have subsidence.
Generally, cracks with a width of less than 0.3 mm are acceptable and do not affect the structure. However, they may develop and grow to become structural cracks. Therefore, one should monitor small cracks on houses or structures.
Crazing Is Caused by Tension during Thermal Expansion
It's very common, and it can occur in any glazed Pottery piece at any point in its lifetime.
Porcelain tile has the same color throughout the material. A broken or chipped piece of unglazed porcelain will have a uniform color throughout its thickness. Ceramic tile often has a glazed surface coloring, so chips may reveal a different color underneath. The finish of porcelain is smoother than that of ceramic.
Porcelain is denser and harder than ceramic, so it's more resistant to chipping. However, its increased brittleness means that it may be more likely to crack upon heavy impact. Despite this, it is a bit more durable than regular ceramic and can last 75 to 100 years with proper maintenance.
Generally, porcelain will melt or break when you subject it to temperatures above 1600C. This temperature is attainable when you expose porcelain tile to direct heat, such as that of a fireplace. Direct exposure will cause the porcelain to crack, melt or even explode.
Because it is fabricated in high heat over 2000° F, porcelain can easily hold its own against hot kitchen or bathroom environments. Its surface is resistant to damage after exposure or contact with hot pans and pots and won't burn, smoke, or emit harmful substances.
Pour Hot Water into the Toilet
If you need to heat some in the microwave or the stovetop, you don't want it to reach boiling temperatures. Boiling water can cause toilet porcelain to crack. Allow the hot fluid to sit in the toilet for a few minutes to loosen the clog.