Crazing describes a fine network of cracks appearing in the glossy surface of a dish’s glaze, fundamentally compromising the protective barrier of the ceramic ware. The core safety question is whether these cracked dishes still offer a hygienic surface for food and drink. This article will examine the two major health considerations associated with using crazed dishes: the risk of biological contamination and the potential for chemical leaching.
Understanding Crazing
Crazing occurs when there is an incompatibility between the ceramic body and the glaze applied to its surface. This happens when the glaze and the underlying clay body expand and contract at different rates during cooling or subsequent temperature changes. This mismatch in thermal expansion creates tension within the glaze, eventually exceeding its strength and causing the fine cracks to form. The protective, smooth surface of the dish is then compromised by these fractures.
The cracks may appear immediately after the firing process, or they can develop over time due to factors like thermal shock, such as placing a hot dish into cold water, or moisture absorption. Earthenware ceramics, which are naturally more porous, are particularly susceptible to delayed crazing as the ceramic body slowly absorbs moisture from the environment, causing it to expand and stress the glaze. Once the glaze’s integrity is breached, the dish’s ability to maintain a non-porous, sealed surface is destroyed.
The Risk of Bacterial Contamination
The microscopic network of cracks created by crazing poses a significant hygiene hazard because it traps food particles and moisture. These narrow crevices provide an ideal, protected environment for bacteria, mold, and mildew to colonize the dish. Since the glaze barrier is no longer intact, the porous ceramic body underneath is exposed, allowing liquids and organic matter to soak in and support microbial growth. Pathogens such as Salmonella and E. coli can establish colonies deep within the crazing network, protected from basic cleaning methods.
Sanitizing crazed dishes is extremely difficult because the cracks shield the contaminants from the full effect of washing. Water and detergent cannot penetrate sufficiently to reach and eliminate organisms sheltered deep within the crevices. Even the high temperatures of a dishwasher may not be enough to eradicate colonies insulated within the ceramic matrix, leading to potential recontamination of fresh food with each use.
Potential for Chemical Leaching
Beyond bacterial concerns, crazing significantly elevates the risk of chemical leaching. The underlying glaze material, particularly in older or artisan pieces, may contain heavy metals like lead and cadmium. Crazing exposes these chemicals, allowing them to migrate out of the glaze and into any food or liquid that comes into contact with the dish. Lead is commonly used to help glazes flow better at lower temperatures, while cadmium is often used to achieve bright colors.
The leaching process is accelerated by several factors, including the presence of acidic foods like tomato products, citrus fruits, and vinegar. Hot foods and prolonged contact time also increase the rate at which these toxic metals dissolve and enter the food. Dishes manufactured before the 1970s pose a particularly high risk, as their glazes often contained high levels of lead. Even small amounts of lead are a concern because the metal builds up in the body over time, potentially causing chronic health issues, especially in children.
Guidelines for Continued Use and Retirement
If a piece is vintage, brightly colored, or was made without verifiable modern safety standards, it should be immediately relegated to decorative use only. The combination of potential heavy metal leaching and the inability to sanitize the surface makes these items unsuitable for contact with food, especially acidic or hot foods.
If you choose to use a crazed dish for occasional, low-risk serving, certain precautions should be followed. Always use a barrier, such as parchment paper or a doily, to separate the food from the cracked glaze. Avoid placing crazed items in the microwave or oven, as heat dramatically increases both thermal shock and the rate of chemical leaching. When washing, hand-wash immediately after use rather than allowing food to sit and soak into the cracks.