Introduction

Bone china, celebrated for its elegance and translucent beauty, is a timeless favorite in households and high-end dining establishments. However, beneath the surface of this delicate ceramic, there is a hidden quality problem – crazing for certain pieces, not for bone china only, but for all ceramic tableware.

Crazing is a subtle network of fine cracks that can mar the glazed surface of bone china tableware. These cracks are not only unsightly but also raise serious concerns about hygiene and safety. In this exploration, we unveil the enigma of crazing in bone china, shedding light on what it is, why it occurs, and the grave implications it holds for both manufacturers and consumers.

What is Crazing?

Crazing refers to the appearance of tiny, hairline cracks on the glaze of ceramics, including bone china tableware. The glaze, which serves both an aesthetic and functional purpose, acts as a shiny, protective coating that prevents the absorption of food and liquids.

Causes of Crazing on Chinaware

Crazing primarily results from the mismatch in thermal expansion rates between the glaze and the ceramic body during the firing process. As ceramics expand with heat and contract during cooling, stress is generated. If the glaze doesn’t match these movements, cracks can form. Additionally, factors such as improper material composition and inadequate temperature control in production can contribute to crazing.Crazing can be caused at different stages of production.

Detecting Crazing

Crazing is not always easily visible to the naked eye, but checking carefully with your eyes is a handy method and the most effective way to spot the crazing.

There is a method suggested online to pour black ink into the tableware and leave it for some time. Then wipe clean. If you can see a black line, then it’s crazed. The reason behind it is that the healthy glaze surface should not be porous; it doesn’t allow liquid to pass through, otherwise, there is a crack. This is not practical, as usually we wouldn’t pour black ink on the tableware we use.

To identify the crazing of bone china tableware, two common methods are used:

Sound Test

Commonly used by the quality inspectors of bone china factories. Gently tapping two pieces of tableware together can reveal the difference in sound between crazed and non-crazed products. Crazed items often produce a dull thud, while intact pieces produce a crisper sound.

Sound comparison of a fine bone china mug and a crazed bone china tableware.

Listen carefully to the sound, you should be able to notice the difference.

Visual Inspection

Scrutiny, especially at connection points and interface areas, may uncover subtle cracks that are characteristic of crazing.

Cracks usually happen at these joint places. These hair lines can be short or long, while for bone china tableware with decorations, the lines are easier to spot; for pure white bone china, the lines are more invisible.

Sometimes the sound difference would not be obvious, and the crazing cracks could be very short, which would require us to check carefully with both methods.

Damage from the Crazing can be caused

In Production

• Crazing can lead to kiln instability and the risk of damaged products, which can affect the entire production process.
• Production costs may rise, especially for larger or irregularly shaped items with higher crazing rates.
• Detecting tiny crazing during production can be challenging, leading to potential quality issues.

In Usage

• Crazing affects the functionality of tableware, making it weaker and more prone to breaking. The crazed tableware could cause serious damage during usage. It might be when you serve your friend hot coffee, propose a toast, or host a big meal with a large pot of delicious food that the craze suddenly expands and the tableware turns into pieces.
• Even if it does not split, the tiny cracks can harbor bacteria, raising hygiene concerns. Food and beverages may penetrate crazed surfaces and be absorbed by the ceramic body, compromising safety.

The impact of crazed tableware

Impact on Businesses

For manufacturers, the presence of crazed functional ware can lead to significant problems. Crazed products are considered defective and are often returned by customers. This can result in damage to a company’s reputation, loss of customers, and potential liability for injuries resulting from the use of these products.

Impact on Consumers

Crazing profoundly affects the functionality, safety, and strength of tableware. The cracks and their access to the possibly porous body below can provide a hospitable environment for bacterial growth, necessitating extra care in cleaning and sterilizing the tableware.

Is it Safe to Use Crazed Dishes?

It is not recommended to use cracked dishes due to the following reasons:

Health is always the first concern. We recommend you throw away the crazed bone china tableware pieces immediately for the following reasons.

Hygiene Concerns: Crazed tableware can provide a breeding ground for bacteria due to the presence of cracks and crevices.

Safety Risks: Crazing weakens dishes, making them more likely to break, which can pose hazards in the kitchen and dining area. 

Crazing compromises the strength of dishes, making them less safe for use in the kitchen or dining room. Dishes with crazing are more likely to break when subjected to everyday use.

Click here if you have concerns about the care of bone china tableware.

Conclusion

Crazing may seem like a cosmetic flaw, but it’s far more than that. It impacts the safety, usability, and trust in bone china products. For manufacturers, it’s a sign of production imbalance. For users, it’s a silent risk.

By understanding what causes crazing and how to detect it, both makers and buyers can make better-informed choices. At Longway Ceramics, our commitment is to uphold the quality, safety, and beauty that bone china deserves.