How to Test the Antimicrobial Performance of Materials

Industrial Materials & Microbial Protection · Admire Technical Resources

When a manufacturer claims that a material has antimicrobial protection, one question naturally follows: how is that performance actually tested? Antimicrobial performance cannot be determined simply by looking at the material or by knowing which antimicrobial agent was used. The result depends on the material, target microorganisms, test method, application method, and testing conditions.

Different materials may require different approaches. A method suitable for a textile may not be appropriate for an incorporated antimicrobial additive in plastic, while a test for antibacterial activity does not automatically demonstrate antifungal or anti-mold performance.

This guide explains how antimicrobial performance is typically evaluated, which factors matter, and how manufacturers can interpret test results more effectively.

What Does an Antimicrobial Test Actually Measure?

An antimicrobial test is designed to determine whether a treated material shows activity against specified microorganisms under defined test conditions. Depending on the method, the evaluation may involve comparing a treated specimen with an untreated control and measuring differences in microbial growth or survival.

The test may focus on:

• Antibacterial activity
• Antifungal or mold-related performance
• Microbial growth inhibition
• Reduction in viable microorganisms
• Performance after aging or other exposure conditions

The exact result depends on the test method and the claim being evaluated. A test result should always be interpreted together with the microorganism, material, method, and test conditions used.

Why Is the Test Method So Important?

There is no single antimicrobial test method that is suitable for every material and every application.

A textile, plastic, coating, rubber component, or silicone product can have very different surface properties and application methods. For example:

• A textile may be evaluated using a method specifically designed for treated textile products.
• A plastic or other non-porous surface may be evaluated using a method designed for antibacterial activity on treated surfaces.
• An antimicrobial additive incorporated into a polymer may require a method that evaluates incorporated or bound antimicrobial agents.
• A plastic exposed to fungi or bacteria may require a different evaluation focused on microbial deterioration rather than antibacterial activity.

This is why selecting a test method should come after understanding the intended application, not before.

What Are the Main Steps in an Antimicrobial Test?

Although individual standards differ, antimicrobial performance evaluation commonly involves several basic stages.

1. Define the Test Objective

First determine what you want to demonstrate. For example:

• Antibacterial activity
• Antifungal activity
• Mold resistance
• Performance after washing
• Performance after UV exposure
• Long-term antimicrobial durability

A clear test objective helps determine the most appropriate test method.

2. Define the Target Microorganisms

The microorganisms selected for testing should reflect the intended claim and application. A product tested against selected bacteria should not automatically be described as effective against fungi or mold. Likewise, a broad-spectrum claim should be supported by appropriate testing against the relevant microorganisms.

3. Prepare Treated and Control Samples

The antimicrobial material is normally compared with an appropriate untreated or reference sample. The specimens should represent the actual material and processing conditions as closely as practical. For an additive incorporated into a polymer, for example, the test specimen should ideally be produced using the intended formulation and processing process rather than an unrelated laboratory substrate.

4. Expose the Samples to the Test Microorganisms

The selected microorganisms are brought into contact with the test specimens according to the chosen method. The exposure conditions, inoculation approach, and contact period depend on the applicable test method.

5. Measure the Microbial Response

The test then measures the response of the microorganisms. Depending on the method, this may involve microbial counts, comparison between treated and untreated samples, visual assessment, percentage reduction, or other defined indicators of antimicrobial activity.

6. Interpret the Result

The result should be interpreted in the context of the complete test setup. A numerical result without information about the test method, microorganisms, material, and conditions can be misleading.

Common Antimicrobial Test Methods by Material

Different materials and claims may be evaluated using different standards.

Plastics and Other Non-Porous Surfaces

ISO 22196:2011 specifies a method for evaluating the antibacterial activity of antibacterial-treated plastics and other non-porous product surfaces. ISO states that the method is intended for treated surfaces and should not be confused with methods for evaluating microbial deterioration of untreated plastics.

For incorporated antimicrobial agents in polymeric or hydrophobic materials, ASTM E2180-24 provides a quantitative method focused primarily on antibacterial activity. ASTM notes that the method can be used for incorporated or bound antimicrobial agents in materials such as plastics and other hydrophobic surfaces, and can also be used to assess persistent activity over time.

Textiles

For textile products, ISO 20743:2021 specifies quantitative methods for determining antibacterial activity. It applies to textile products including nonwovens and covers different methods of inoculating test specimens depending on the intended application and surface characteristics.

AATCC TM100 is another established method for quantitatively assessing antibacterial finishes on textile materials. AATCC describes it as a procedure for evaluating the degree of antibacterial activity intended for the use of the textile material.

Plastics and Fungal or Microbial Deterioration

ISO 846:2019 addresses the deterioration of plastics due to fungi, bacteria, and soil microorganisms. The standard evaluates deterioration through methods such as visual examination and changes in mass or other physical properties. The current 2019 edition was reviewed and confirmed in 2024.

This is an important distinction: antibacterial activity testing and fungal or microbial deterioration testing do not answer exactly the same question. A test selected for one claim should not automatically be used to support another.

Antibacterial Testing vs. Antifungal or Anti-Mold Testing

These terms are often used interchangeably in marketing, but they represent different performance questions.

A material that shows antibacterial activity is not automatically proven to provide mold protection. Likewise, evidence of fungal resistance does not automatically establish antibacterial performance. The microorganism tested should match the protection claim being made.

Why Is an Untreated Control Important?

An untreated control helps provide a reference point for evaluating the effect of the antimicrobial treatment. Without an appropriate control, it can be difficult to determine how much of the observed result is associated with the treatment itself.

For this reason, comparative testing between treated and untreated specimens is an important part of many antimicrobial evaluation methods. The control should ideally be representative of the same material system without the antimicrobial treatment, so that differences can be interpreted more meaningfully.

How Should Antimicrobial Test Results Be Reported?

A useful antimicrobial test report should provide enough information to understand what was actually tested. Important information may include:

• Material tested
• Antimicrobial treatment or additive
• Target microorganisms
• Test method or standard
• Sample preparation
• Exposure or contact conditions
• Test result
• Reference or control sample
• Any aging or pre-treatment applied

This information matters because the same antimicrobial product may perform differently when used in another material or under different processing conditions.

Does a Good Laboratory Test Guarantee Real-World Performance?

Not necessarily. A laboratory test evaluates antimicrobial performance under defined conditions. Those conditions may not reproduce every factor encountered during actual product use.

Real-world performance can also be influenced by:

• Washing
• UV exposure
• Heat
• Humidity
• Abrasion
• Chemical cleaning
• Material aging
• Formulation changes
• Processing variations

For this reason, laboratory testing and application-specific evaluation should be considered together when long-term performance is important.

How to Test Antimicrobial Durability

When durability is an important requirement, the testing process may include an additional exposure or aging stage before antimicrobial performance is measured again.

A simplified evaluation model is:

Initial Antimicrobial Test → Relevant Aging or Exposure → Repeat Antimicrobial Test → Compare Performance

The exposure conditions should reflect the intended application as closely as practical. For example, textile products may require washing-related evaluation, while outdoor plastic products may require consideration of UV and weathering exposure.

This approach connects directly with our previous guide: How Long Does Antimicrobial Protection Last?

Common Mistakes When Evaluating Antimicrobial Performance

Choosing the Wrong Test for the Material

A test method developed for one material type may not be appropriate for another.

Testing the Wrong Microorganisms

A test against selected bacteria does not automatically support an antifungal or anti-mold claim.

Ignoring the Untreated Control

Without a suitable reference sample, the contribution of the antimicrobial treatment may be difficult to evaluate.

Looking Only at the Initial Result

A strong initial result does not necessarily demonstrate long-term durability.

Treating Laboratory Results as Universal

A laboratory result applies to the tested material, method, and conditions. It should not automatically be generalized to every formulation or application.

Changing the Formulation After Testing

If the material formulation, additive level, processing conditions, or application method changes significantly, the previous test result may no longer fully represent the new product.

How to Build a Practical Antimicrobial Testing Strategy

For manufacturers developing or evaluating an antimicrobial material, a practical sequence is:

1. Step 1 — Define the Application: What is the material, where will it be used, and what performance is required?
2. Step 2 — Define the Target Microorganisms: Determine whether the objective is antibacterial, antifungal, anti-mold, or broader microbial protection.
3. Step 3 — Select the Appropriate Test Method: Choose a method suitable for the material and intended claim.
4. Step 4 — Test the Actual Material System: Use representative formulations, processing conditions, and specimens whenever practical.
5. Step 5 — Compare With an Untreated Control: Evaluate the difference between treated and untreated samples.
6. Step 6 — Consider Durability: Add relevant washing, UV, heat, abrasion, chemical, or other exposure conditions when required.
7. Step 7 — Review the Results in Context: Use the complete test information rather than relying on a single number or marketing statement.

Good antimicrobial testing is not simply about obtaining a high reduction value. It is about generating evidence that is relevant to the material, microorganism, application, and intended claim.

Frequently Asked Questions

Which test is suitable for antimicrobial plastics?

The appropriate method depends on the intended claim and material. ISO 22196 is specifically designed to evaluate antibacterial activity on treated plastics and other non-porous surfaces, while ASTM E2180-24 focuses on incorporated or bound antimicrobial agents in polymeric or hydrophobic materials.

Which test standard is used for antibacterial textiles?

ISO 20743:2021 provides quantitative methods for determining antibacterial activity in textile products, while AATCC TM100 is another established method for assessing antibacterial finishes on textile materials.

Does an antibacterial test prove anti-mold performance?

No. Antibacterial testing evaluates bacteria, while antifungal or mold-related claims require appropriate evaluation against fungi or mold under a suitable method.

Can the same antimicrobial test be used for every material?

No. Test method selection should consider the material, antimicrobial technology, target microorganisms, surface characteristics, and intended application.

Should an untreated sample be tested?

In many comparative antimicrobial evaluations, an untreated control is important for understanding the effect of the treatment. The exact control design depends on the applicable test method.

Can antimicrobial performance be tested after washing or aging?

Yes. Durability evaluations can include relevant exposure conditions followed by repeat antimicrobial testing. ASTM E2180-24, for example, notes that the method can be used to assess persistent antimicrobial activity over time.

Does passing one antimicrobial test mean the material is suitable for every application?

No. A test result applies to the tested material, microorganisms, method, and conditions. Additional testing may be appropriate when the formulation, processing conditions, target microorganisms, or end-use environment changes.

Need Help Evaluating Antimicrobial Performance?

Choosing the right antimicrobial test starts with understanding the material, target microorganisms, processing conditions, and intended application.

Contact our technical team with your material type, antimicrobial system, target microorganisms, and application requirements. We can help identify relevant testing considerations for your application.