Magnetic Properties of Ceramic Minerals – Part 2

In our previous two blog posts, we introduced the problems caused by magnetic minerals in ceramic production and examined in detail the five different magnetic properties that minerals may exhibit. In this blog, we will discuss the consequences of magnetic particle contamination in ceramics when magnetic separation is not used.

Consequences of Magnetic Particle Contamination in Ceramic Minerals

Magnetic particles may exist in mineral form, or as free iron particles present in ceramic bodies or glazes.

Regardless of their form, the presence of these particles can lead to various problems during the firing and processing of ceramic materials. In the past, ceramic manufacturers were able to hide such visual defects using colored and decorative glazes. However, with the growing popularity of plain white ceramics in particular, modern ceramic producers no longer have the luxury of concealing defects with decorative patterns.

The presence of magnetic particles in ceramics can cause structural and surface defects as well as color and gloss problems. Visible black spots and glaze deformations are especially common in low-cost mass-produced ceramics.

In addition, although less obvious, brown or black pinpoint stains are also a frequently encountered issue. These defects result from magnetic minerals or free iron present in the glaze during firing. During the firing process, magnetic particles or free iron absorb and retain heat, causing the particles to expand and darken in color. In some cases, these particles may “burst,” leading to defects in the surrounding glaze layer.

Another significant problem is the unintended change in the final glaze color. This issue is particularly common in white or light-colored ceramics. The presence of fine magnetic particles can affect the final fired glaze color, reducing overall brightness and creating a serious aesthetic defect.

In products that must be aesthetically flawless—such as ceramic tiles, tableware, and sanitary ware—these types of defects require parts to be partially reprocessed or completely rejected and sent for recycling. If a facility does not have an adequate magnetic particle removal system, the rejection rate can exceed 10%, leading to significant costs in terms of both time and materials.

In addition to visible defects, non-visible magnetic contamination can also cause major problems. Magnetic particles remaining in the ceramic body before firing expand when exposed to heat, similar to those in the glaze, weakening the surrounding ceramic structure. Over time, this can lead to the formation of microcracks and eventually cause complete failure of the ceramic product.

When a ceramic product breaks, the presence of magnetic particles along the fracture line is often noticeable. Even a single magnetic particle can cause severe cracking and ultimately result in complete structural failure. This is a major concern in high-performance ceramics, as this initially invisible contamination only becomes apparent over time and leads to product failure.

Magnetic separation is a highly effective method for removing magnetic particle contamination in ceramic production processes. In our next blog post, we will discuss in more detail how different magnetic separation methods can be effectively applied in ceramic processing applications.

For more information about customized magnetic separation solutions for your ceramic production processes, please contact Aksa Magnet.

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