In the case of less durable materials such as porcelain, fiberglass, wood and glass, these materials will eventually break down and erode if exposed to drastic temperature shifts over long periods of time. These usually will manifest as cracks, material stripping or warping.
One of the most common causes of hairline cracks on porcelain sinks is thermal stress. Considering porcelain is usually layered on metal (which conducts heat), the sink loses heat rapidly and can become very cold—even when the room isn't cold.
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.
Every material will age over time. With that age, bathroom sinks can begin to show hairline cracks. To make your sink last longer, you should repair these hairline cracks as soon as you can.
Porcelain sinks are both beautiful and easy to clean. On the down side, it's a brittle material and easily cracked. One drop of a heavy object can leave you staring at a major chip in your porcelain. If you have a cast iron porcelain overlay sink, you will probably see a black mark under the chip.
Heavy usage can result in cracks appearing or the unintentional dropping of a hefty object on the porcelain can chip off parts of the enamel. All these chips and cracks can be unpleasant to look at and might prompt you to want to replace the sink.
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.
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. Most ceramics expand slightly on heating and contract on cooling.
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.
In the case of less durable materials such as porcelain, fiberglass, wood and glass, these materials will eventually break down and erode if exposed to drastic temperature shifts over long periods of time. These usually will manifest as cracks, material stripping or warping.
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.
Uneven drying of the piece causes cracking, which means that certain portions of the pottery shrink more than others. The key to avoiding these hazards is to dry the item in a constant atmosphere and to do the required prep work to guarantee that the entire piece dries at the same rate.
Small or hairline cracks are usually nothing to worry about.
Slight — minor cracks between 1mm and 5mm in width, which can be fixed with filler. You might need to repoint exterior cracks. Moderate — cracks between 5mm and 15mm may need professional building work and there might be underlying repairs.
Hairline cracks of less than one millimetre in width or slight cracks of between one and five millimetres are generally not a cause for concern.
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.
Porcelain is less likely to crack under extreme heat, whereas ceramic can become damaged, cracked, or even change shape when exposed to extreme heat.
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. Crazing can make foodsafe glazes unsafe and ruin the look of a piece.
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.
Abrasive cleaners: Abrasive cleaners that contain harsh chemicals can stain, scratch, or damage the finish on porcelain sinks.
Pouring boiling water directly into a cold porcelain or stoneware cup, bowl or mug may cause the item / glaze to crack (thermal shock).
Porcelain sinks have an average lifespan of 20–25 years. While all materials take on wear and tear over time, porcelain sinks can be refinished to keep them looking brand new and gorgeous for decades.