ASTM G-21 Testing Available at EMSL

ASTM G21 Testing – Fungal Resistance Testing

Category	Press Release
Publish Date	10/7/2026
Author	Joe Frasca
Title	ASTM G-21 Testing Available at EMSL
Introduction	Fungal Resistance Testing for Materials
ASTM G21 Testing – Fungal Resistance Testing for Plastics and Polymeric Materials ASTM G21 testing is used to evaluate the resistance of synthetic polymeric materials to fungal growth. Manufacturers, product developers, material suppliers, engineers, and quality professionals can use ASTM G21 testing to determine whether plastics, polymers, coatings, components, and other synthetic materials are susceptible to fungal colonization under controlled laboratory conditions. ASTM G21, Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi, provides a standardized approach for exposing materials to fungi and evaluating visible fungal growth. Professional ASTM G21 testing can help manufacturers evaluate material performance, compare formulations, support research and development, investigate product failures, and demonstrate resistance to fungal growth. What Is ASTM G21 Testing? ASTM G21 is a laboratory practice designed to determine the resistance of synthetic polymeric materials to fungi. Many synthetic polymers are naturally resistant to fungal attack because they may not provide nutrients that fungi can readily utilize. However, finished products frequently contain additional materials that can affect fungal resistance. These may include: Plasticizers Lubricants Stabilizers Colorants Fillers Processing aids Organic additives Surface contaminants Coatings Adhesives Environmental exposure can also introduce dust, oils, nutrients, and other contaminants that promote fungal growth. ASTM G21 testing provides a controlled method for determining whether fungal growth can develop on or affect a material. Why Is ASTM G21 Testing Important? Fungal growth on materials can cause both cosmetic and functional problems. Depending on the material and its intended use, fungal contamination may contribute to: Surface discoloration Staining Odors Material degradation Changes in appearance Loss of physical properties Reduced product durability Damage to coatings or finishes Product quality concerns Customer complaints ASTM G21 testing can help determine how a material performs when exposed to fungi under conditions designed to encourage fungal growth. Materials Commonly Evaluated Using ASTM G21 ASTM G21 fungal resistance testing may be appropriate for a wide range of synthetic polymeric materials and manufactured products. Examples may include: Plastics and Polymers Thermoplastics Thermoset plastics Polymeric films Plastic sheets Molded plastic components Flexible plastics Elastomeric materials Coatings and Surface Materials Polymer coatings Protective finishes Painted polymer surfaces Sealants Caulks Membranes Electrical and Electronic Materials Wire insulation Cable jackets Electrical enclosures Plastic electronic components Polymeric housings Construction Materials Polymeric building products Insulation components Plastic panels Flooring materials Roofing materials Sealants and membranes Automotive and Transportation Materials Interior polymer components Plastic trim Wire and cable materials Elastomers Coated components Consumer and Industrial Products ASTM G21 testing may also be useful for polymeric materials used in appliances, industrial equipment, packaging, consumer goods, storage products, and other applications where resistance to fungal growth is important. How Does ASTM G21 Fungal Resistance Testing Work? During ASTM G21 testing, prepared specimens are exposed under controlled laboratory conditions to fungal organisms specified by the applicable procedure. The test environment is designed to promote fungal growth so that the resistance of the test material can be evaluated. After the specified exposure period, samples are examined for evidence of fungal growth. Results can provide useful information about the relative fungal resistance of a material or product. Testing should be performed according to the applicable version of ASTM G21 and any customer-specific requirements. ASTM G21 Test Results ASTM G21 results are generally based on the amount of visible fungal growth observed on the test specimens. The resulting evaluation can help determine whether the material demonstrates: Little or no observable fungal growth Limited fungal growth Moderate fungal colonization Extensive fungal growth Interpretation should consider the material, product specifications, customer requirements, and intended end use. ASTM G21 is a resistance evaluation and should not automatically be interpreted as proof that a product will remain completely fungus-free under every real-world environmental condition. ASTM G21 Testing for Product Development ASTM G21 testing can be particularly valuable during material selection and new product development. Manufacturers can use fungal resistance testing to compare: Different polymer formulations Competing raw materials Additive packages Coatings Plasticizers Preservatives Manufacturing processes Prototype materials Testing multiple formulations can help product developers determine which material provides the desired level of fungal resistance before a product reaches full-scale production. ASTM G21 Testing for Quality Control Manufacturers may also incorporate ASTM G21 testing into quality assurance programs. Testing may help evaluate: Raw material changes Supplier changes Reformulated products Production changes Material substitutions Product complaints Suspected fungal susceptibility Changes in additives or coatings Periodic laboratory testing can provide valuable information about whether product modifications have affected fungal resistance. ASTM G21 Testing for Antifungal Materials Companies developing materials marketed for fungal resistance may use ASTM G21 as part of their product evaluation program. Potential applications include materials incorporating: Antifungal additives Biocidal treatments Preservatives Antimicrobial technologies Fungistatic formulations The appropriate test method should always be selected based on the product, intended claims, applicable regulations, and performance objectives. Industries That May Need ASTM G21 Testing ASTM G21 testing can support manufacturers and organizations across numerous industries, including: Plastics manufacturing Polymer manufacturing Construction products Building materials Automotive Aerospace Electronics Wire and cable Consumer products Industrial equipment Appliances Packaging Coatings Adhesives and sealants Research and development Material manufacturing ASTM G21 vs. General Mold Testing ASTM G21 testing is different from environmental mold testing. Environmental mold testing typically involves evaluating air, surfaces, dust, or building materials to determine whether mold contamination is present. ASTM G21 is instead a controlled laboratory evaluation of a synthetic polymeric material's resistance to fungal growth. Companies searching for mold resistance testing, fungal resistance testing, or polymer fungus testing may therefore require ASTM G21 depending on their material and testing objectives. Benefits of ASTM G21 Fungal Resistance Testing ASTM G21 testing can provide manufacturers with valuable information during product development and quality assurance. Potential benefits include: Comparing material formulations Evaluating fungal resistance Supporting material selection Investigating product failures Evaluating supplier changes Supporting product development Assessing coatings and additives Identifying susceptibility to fungal growth Providing standardized laboratory data ASTM G21 Laboratory Testing Services When selecting an ASTM G21 testing laboratory, look for a laboratory with experience in microbiology, fungal testing, polymeric materials, and standardized testing procedures. Before submitting samples, provide as much information as possible about: Material composition Product type Sample dimensions Number of specimens Intended use Applicable specification Required version of ASTM G21 Customer acceptance criteria Reporting requirements Special conditioning requirements Providing these details can help ensure that the laboratory develops an appropriate testing approach. Submit Samples for ASTM G21 Testing If you manufacture plastics, polymers, coatings, building materials, electrical components, automotive products, or other synthetic materials, ASTM G21 testing can help determine their resistance to fungal growth. Contact EMSL Analytical at [email protected] to discuss your ASTM G21 testing requirements, sample preparation, testing options, turnaround time, and laboratory services. EMSL's laboratory professionals can assist manufacturers, product developers, consultants, engineers, and quality-control professionals with microbiological and material testing needs. Contact EMSL Analytical today for information about ASTM G21 fungal resistance testing and laboratory services. Frequently Asked Questions About ASTM G21 Testing What does ASTM G21 test for? ASTM G21 evaluates the resistance of synthetic polymeric materials to fungal growth under controlled laboratory conditions. What is the full name of ASTM G21? ASTM identifies the standard as Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi. What materials can be tested using ASTM G21? Testing may be performed on appropriate plastics, polymers, coatings, films, insulation materials, elastomers, and other synthetic polymeric materials. Is ASTM G21 a mold resistance test? ASTM G21 is commonly associated with fungal or mold resistance testing of synthetic polymeric materials. It evaluates fungal growth under standardized laboratory exposure conditions. Why would a manufacturer perform ASTM G21 testing? Manufacturers may use ASTM G21 for material qualification, product development, formulation comparisons, quality assurance, failure investigations, or evaluation of fungus-resistant materials. Can ASTM G21 be used to compare different materials? Yes. When samples are tested under comparable conditions, the procedure may provide useful information for comparing the fungal resistance of different materials or formulations. Where can I get ASTM G21 testing performed? EMSL is experienced with standardized fungal resistance testing can determine whether ASTM G21 is appropriate for your product and testing objectives. Email EMSL for pricing and information at [email protected]