Antibacterial ceramics: development, technologies and industrial validation

The functionalisation of ceramic surfaces makes it possible to incorporate performance features that go beyond aesthetics and resistance. One of these is antibacterial activity, a property that is particularly relevant for products intended for spaces where hygiene, ease of cleaning and control of surface contamination are especially important.

However, developing antibacterial ceramics is not simply a matter of adding an active component to the glaze. Effectiveness depends on how it is incorporated, how it interacts with the rest of the formulation, how it behaves during firing and how available it remains on the finished surface.

From the ceramic color manufacturer’s perspective, we need to approach this functionality as part of the complete ceramic system. The goal is not to achieve a good result on an isolated sample, but to formulate a solution that maintains its activity, technical performance and appearance when transferred to industrial production.

In this article, we explain how…

• Antibacterial activity must be designed as part of the ceramic system.

• Each technology has its own mechanism of action and specific test method.

• The glaze, firing process and surface finish influence effectiveness.

• Validation must be carried out on the finished ceramic piece.

• Industrial scale-up requires stability and repeatability from batch to batch.

What are antibacterial ceramics?

Antibacterial ceramics are ceramic materials whose surface incorporates a technology designed to inhibit the growth of certain bacteria or reduce their presence under defined test conditions.

This definition is important because the term “antibacterial” does not imply absolute protection or mean that the surface will remain free of microorganisms under all circumstances. Demonstrated activity is always linked to specific bacteria, a defined contact time and a particular evaluation method.

Nor should it be understood as a substitute for cleaning. It is an additional performance feature that can help limit bacterial proliferation on the surface, but it does not remove the need to follow standard maintenance, cleaning and disinfection protocols.

Antibacterial, antimicrobial and self-cleaning are not synonymous

The term antibacterial refers specifically to activity against bacteria. Antimicrobial, on the other hand, covers a broader range of microorganisms and should therefore only be used when testing supports the claimed activity against each of them.

A photocatalytic surface contains a semiconductor material that requires specific irradiation conditions in order to become active. This property may be associated with pollutant degradation or activity against bacteria, but these effects must be evaluated separately.

Likewise, a self-cleaning surface may facilitate the degradation or removal of certain residues without this automatically demonstrating antibacterial activity.

How antibacterial activity is achieved in ceramics

There are different ways to functionalise a ceramic surface. The choice depends on the product, the manufacturing process, the conditions of use and the type of activity to be demonstrated.

Silver-based systems and other metal ions

Silver is one of the most widely studied agents for the development of antibacterial ceramic surfaces. It can be incorporated into a ceramic frit, the glaze, a functional suspension or a coating applied to the surface.

Its activity is related to the availability of silver species capable of interacting with bacteria. Therefore, knowing the total amount incorporated is not enough. We also need to analyse how it is distributed after firing and what fraction remains accessible at the surface.

Recent studies have succeeded in developing silver-containing glazes and scaling them up to industrial facilities while maintaining high activity against Escherichia coli and Staphylococcus aureus. These studies also show that the lower reproducibility of industrial thermal cycles can increase variability in the results.

Other research has incorporated silver-bearing compounds directly into the glaze and fired them at 1,200 °C in industrial kilns. The results link effectiveness to the presence of silver ions at the surface and to good particle dispersion within the glaze.

This confirms a fundamental principle for ceramic color manufacturers: a higher concentration does not necessarily mean higher activity. Dispersion, integration within the glassy matrix and surface exposure are decisive.

Photocatalytic technologies

Another approach involves the use of semiconductor materials, such as titanium dioxide, which are capable of generating reactive species when exposed to suitable irradiation. These species can degrade organic matter and act on microorganisms present on the surface.

Integrating this technology into ceramics presents a thermal challenge. Conventional firing temperatures can transform the crystalline phase of titanium dioxide and reduce its photocatalytic performance. For this reason, some developments use surface applications or post-treatments that better preserve the active phase.

Not all photocatalytic technologies operate under the same light source or intensity. Nor should they be described as active in darkness unless the formulation combines other mechanisms that are independent of irradiation and these have been specifically evaluated.

Integration into the glaze or surface treatment

The functionality can be incorporated before firing or applied through a subsequent treatment.

Integrating the active agent into the glaze facilitates its incorporation into the standard production process and may improve durability. However, the glassy phase can encapsulate part of the component and reduce its availability at the surface.

Post-firing treatments act directly on the finished surface, although their adhesion, chemical resistance, wear resistance and stability under cleaning procedures must be evaluated.

Intermediate solutions also exist. An industrial study published in 2025, “Preparation and testing of the activity of antibacterial coatings on polished ceramic tiles obtained in industrial conditions”, developed a multilayer system using silver nanoparticles incorporated before single firing and through a subsequent impregnation treatment. The surfaces were evaluated after abrasion, detergent exposure and contact with acidic and alkaline media, highlighting the importance of assessing durability as well as initial activity.

What the ceramic color manufacturer must control during development

The antibacterial agent is part of a formulation that must continue to meet the requirements expected of a ceramic glaze. Development must therefore balance functionality, industrial performance and aesthetic results.

Compatibility with the glaze

The incorporation of the active agent must not compromise:

• Suspension stability.

• Uniform application.

• Glaze melting and maturation.

• Shade, gloss or transparency.

• Chemical and mechanical resistance.

• The absence of surface defects.

A functional component may alter viscosity, promote sedimentation, modify colour development or influence the formation of crystalline phases. These interactions need to be studied before establishing an industrial dosage.

Dispersion and homogeneity

Uneven distribution can lead to differences in activity within the same piece or between batches. Control must cover particle size, dispersion, sedimentation, dosage and stability throughout the entire application period.

Homogeneity is also essential to prevent apparently satisfactory areas from coexisting with others where the surface concentration is insufficient.

Firing and surface availability

Maximum temperature is not the only relevant parameter. Heating rate, dwell time, atmosphere and cooling also play a role.

During firing, the agent may react with other components, change state, partially volatilise or become encapsulated within the glaze. For this reason, knowing its thermal resistance outside the glaze is not enough to predict its final behaviour.

A 2026 study on tiles with different silver formulations observed that post-firing treatments provided greater activity than some pre-firing incorporations. The authors linked this difference to the reduced availability of silver after exposure to high temperatures and to the influence of surface composition and morphology.

“Towards a comprehensive assessment of antibacterial ceramic tiles: linking surface properties to bacterial adhesion”.

Source: https://www.sciencedirect.com/science/article/pii/S2352186426002932

Gloss, roughness and microstructure

The surface finish also influences antibacterial behaviour. Roughness, porosity and microstructure can affect bacterial adhesion, residue build-up and contact between microorganisms and the active agent.

This means each finish must be validated individually. A result obtained on a smooth, glossy surface should not automatically be extrapolated to a matt, structured or polished version of the same collection.

“Antibacterial activity is not formulated in the laboratory alone. It is built through the glaze, application, firing process and final surface.”

How antibacterial activity is measured

Effectiveness must be evaluated using a method that is appropriate for the technology used and the type of surface.

ISO 22196 for treated non-porous surfaces

ISO 22196:2011 establishes a method for evaluating antibacterial activity on treated plastics and other non-porous surfaces. Its scope excludes photocatalytic materials and also sets out specific considerations for building materials, so the suitability of the method for the product should be confirmed with the laboratory carrying out the testing. The standard was reviewed and confirmed in 2026, meaning the 2011 edition remains the current published version.

The test compares the evolution of bacteria on a treated sample and a control surface under defined conditions. The result is expressed as an activity value or reduction calculated from bacterial counts.

ISO 27447 for photocatalytic materials

Photocatalytic surfaces require a specific evaluation method. ISO 27447:2019 determines the antibacterial activity of semiconductor materials under ultraviolet irradiation and does not evaluate other properties such as antiviral activity, self-cleaning performance or air purification. The 2019 edition remains published, although a revision is currently under development.

Using different standards means working under different conditions. It is therefore not appropriate to directly compare a percentage obtained under ISO 22196 with another obtained from a photocatalytic test under irradiation.

What does a 99.9% reduction mean?

A 99.9% reduction is equivalent to a three-log reduction relative to the reference used in the test. However, the percentage alone does not fully describe the performance.

To interpret it correctly, the following should be specified:

• The bacteria tested.

• Contact time.

• Temperature and humidity conditions.

• The presence and type of irradiation.

• The sample used as the control.

• The calculation method.

• The laboratory that performed the test.

Claims must be limited to what has actually been demonstrated. A result obtained against two bacterial strains does not, by itself, demonstrate general activity against viruses, fungi or other microorganisms.

Testing the finished ceramic piece

A raw material may show activity before being incorporated into the glaze and lose part of that activity during firing. The opposite can also occur: the combination of formulation and thermal treatment may promote the formation of the functional phase.

For this reason, evaluation must be carried out on a representative sample of the product that will reach the market and after any process stages that could modify its surface:

• Firing.

• Polishing or rectification.

• Application of protective coatings.

• Post-treatments.

• Industrial cleaning.

From the laboratory to the industrial line

Development begins by defining the functionality required by the manufacturer. We need to understand the type of product, its intended use, the finish, the microorganisms against which it will be evaluated and the performance characteristics that must be maintained.

From there, we formulate different alternatives and analyse their ceramic behaviour. Initial trials allow us to compare concentrations, incorporation systems, firing cycles and finishes.

The best formulation is not necessarily the one that achieves the highest percentage in the first sample. It must meet four conditions:

1. Demonstrable activity.

2. Compatibility with the process.

3. Aesthetic and technical stability.

4. Industrial reproducibility.

Factory scale-up makes it possible to verify suspension stability, application weight, application homogeneity, kiln response and variation between pieces. Technical literature confirms that transferring an antibacterial glaze to an industrial kiln can increase variability due to the real differences found in thermal cycles.

Once the development has been stabilised, the critical parameters should be documented: dosage, density, viscosity, application weight, thermal curve, finish and controls on the fired piece.

What can reduce effectiveness over time?

Initial validation alone does not guarantee that performance will remain unchanged throughout the product’s service life.

Changes in raw materials, application deviations and variations in firing can alter the presence of the active agent at the surface. Polishing, abrasion or certain treatments may also remove or transform the functional layer.

In addition, dirt and residues from maintenance products can hinder contact between bacteria and the active surface. Instructions for use and cleaning should therefore be compatible with the technology employed.

Where required by the intended use, antibacterial activity should be evaluated after abrasion, ageing, chemical resistance or repeated cleaning tests. The latest industrial research already incorporates this type of testing to determine whether the activity is maintained beyond the newly manufactured sample.

Applications of antibacterial ceramics

This functionality can add value in healthcare environments, care homes, laboratories, educational facilities, sports facilities, professional kitchens and other shared-use spaces.

Each application involves different requirements. Flooring intended for high-traffic areas must combine antibacterial activity with wear resistance and safety in use. A healthcare wall covering must withstand frequent cleaning and chemical products. On a domestic surface, functionality needs to coexist with aesthetics, ease of maintenance and clear communication for the user.

The final application should be part of the product definition from the very beginning. There is no single formulation that is suitable for every substrate, finish or condition of use.

What manufacturers should assess before launch

Before marketing a collection as antibacterial, the manufacturer should ensure that there is consistency between the formulation, the tested product and the message communicated to the market.

In the European Union, articles treated with biocidal products or deliberately incorporating them are subject to the Biocidal Products Regulation. Active substances must be approved or included in the relevant procedures for the intended use. In addition, where an article is claimed to have biocidal properties, specific labelling and information requirements may apply.

This assessment should be carried out with regulatory specialists. As the ceramic color manufacturer, our responsibility is to provide technical information on the formulation, collaborate in the validation process and ensure that the industrial product corresponds to the samples that were evaluated.

At Kerafrit, we understand this type of development as a shared process with the manufacturer’s R&D, product and production teams. We formulate tailored solutions, analyse how they interact with the ceramic system and support testing until a stable operating window is defined. This approach reflects our positioning as a technical partner: designing solutions and moving forward alongside you throughout the entire process.

Developing antibacterial ceramics requires formulation, firing, validation and communication to work in alignment. When all these elements are developed together, functionality stops being an added promise and becomes a real, measurable and reproducible performance feature.

Would you like to incorporate antibacterial activity into a collection or review an existing formulation? At Kerafrit, we study the complete ceramic system and support you from glaze development through to industrial validation.