ASTM D5590-17(2021)

Standard Test Method for Determining the Resistance of Paint Films and Related Coatings to Fungal Defacement by Accelerated Four-Week Agar Plate Assay

SIGNIFICANCE AND USE
4.1 Defacement of paint and coating films by fungal growth (mold, mildew) is a common phenomenon, and defacement by algal growth can also occur under certain conditions. It is generally known that differences in the environment, lighting, temperature, humidity, substrate pH, and other factors in addition to the coating composition affect the susceptibility of a given painted surface. This test method attempts to provide a means to comparatively evaluate different coating formulations for their relative performance under a given set of conditions. It does not imply that a coating that resists growth under these conditions will necessarily resist growth in the actual application. The method is not intended to simulate or replace indoor or outdoor exposure of paint films or related coatings.
Note 1: It is hoped that a ranking of relative performance would be similar to that ranked from outdoor exposures. Paint designated for service in exterior conditions should be pre-conditioned by laboratory accelerated weathering prior to exposure to fungi. All pre-conditioning must be detailed in the final report. This test method however, should not be used as a replacement for exterior exposure (that is, Practice D3456) since many other factors, only a few of which are listed will affect those results.  
4.2 Familiarity with microbiological techniques is required. This test method should not be used by persons without at least basic microbiological training.
SCOPE
1.1 This test method covers an accelerated method for determining the relative resistance of two or more paints or coating films to fungal growth.  
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2021
• ICS: 87.040 - Paints and varnishes
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.28 - Biodeterioration

Relations

• Refers: ASTM D4708-24 - Standard Practice for Preparation of Uniform Free Films of Organic Coatings
• Effective Date: 15-Jan-2024
• Refers: ASTM D1005-95(2020) - Standard Test Method for Measurement of Dry-Film Thickness of Organic Coatings Using Micrometers
• Effective Date: 01-Jun-2020
• Refers: ASTM D4708-19 - Standard Practice for Preparation of Uniform Free Films of Organic Coatings
• Effective Date: 01-Mar-2019
• Refers: ASTM D3456-18 - Standard Practice for Determining by Exterior Exposure Tests the Susceptibility of Paint Films to Microbiological Attack
• Effective Date: 01-Jul-2018
• Refers: ASTM D6132-13 - Standard Test Method for Nondestructive Measurement of Dry Film Thickness of Applied Organic Coatings Using an Ultrasonic Coating Thickness Gage
• Effective Date: 01-Nov-2013
• Refers: ASTM G21-13 - Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi
• Effective Date: 01-Nov-2013
• Refers: ASTM D3456-86(2012) - Standard Practice for Determining by Exterior Exposure Tests the Susceptibility of Paint Films to Microbiological Attack
• Effective Date: 01-Aug-2012
• Refers: ASTM D4708-12 - Standard Practice for Preparation of Uniform Free Films of Organic Coatings
• Effective Date: 01-Jul-2012
• Refers: ASTM D3273-12 - Standard Test Method for Resistance to Growth of Mold on the Surface of Interior Coatings in an Environmental Chamber
• Effective Date: 01-Feb-2012
• Refers: ASTM D3273-12e1 - Standard Test Method for Resistance to Growth of Mold on the Surface of Interior Coatings in an Environmental Chamber
• Effective Date: 01-Feb-2012
• Refers: ASTM D4587-11 - Standard Practice for Fluorescent UV-Condensation Exposures of Paint and Related Coatings
• Effective Date: 01-Jun-2011
• Refers: ASTM D6132-08 - Standard Test Method for Nondestructive Measurement of Dry Film Thickness of Applied Organic Coatings Using an Ultrasonic Gage
• Effective Date: 01-Jul-2008
• Refers: ASTM D3456-86(2008) - Standard Practice for Determining by Exterior Exposure Tests the Susceptibility of Paint Films to Microbiological Attack
• Effective Date: 01-Jun-2008
• Refers: ASTM D6695-08 - Standard Practice for Xenon-Arc Exposures of Paint and Related Coatings
• Effective Date: 01-Jun-2008
• Refers: ASTM D4708-07 - Standard Practice for Preparation of Uniform Free Films of Organic Coatings
• Effective Date: 01-Nov-2007

Overview

ASTM D5590-17(2021) is the standard test method developed by ASTM International for determining the resistance of paint films and related coatings to fungal defacement using an accelerated four-week agar plate assay. Fungal (mold and mildew) and sometimes algal defacement are common issues affecting painted and coated surfaces, especially under conditions of high humidity and moderate temperature. This test method provides a comparative means to assess the performance of coatings in resisting fungal growth when subjected to controlled laboratory conditions, utilizing a standardized agar plate assay over a four-week period.

The standard enables manufacturers, formulators, and quality control laboratories to evaluate and rank the effectiveness of various paint or coating formulations against fungal colonization, contributing to product development, regulatory compliance, and performance claims.

Key Topics

• Fungal Defacement of Coatings: Paint films or coatings can degrade aesthetically and functionally due to growth of mold, mildew, or algae, influenced by moisture, temperature, pH, and substrate.
• Accelerated Agar Plate Assay: The method uses an agar-based microscope assay to expose coated samples to selected fungal species, typically for four weeks under controlled temperature and humidity.
• Comparative Evaluation: The test allows side-by-side comparison of two or more coatings’ resistance to fungal growth, supporting objective assessment of product variations.
• Controls and Ratings: The method involves using positive and negative controls, regular monitoring, and a standardized growth rating scale assessing the degree of fungal coverage on the samples.
• Laboratory Requirements: A basic knowledge of microbiological techniques and safety is essential, as the methodology involves working with live fungal cultures.
• Limitations: While the assay provides valuable comparative data, it does not replicate real-world exterior or interior weathering conditions. Field exposure tests remain essential for fully evaluating long-term performance.

Applications

• Coating Development & QA: Paint and coatings manufacturers use ASTM D5590 as a research and development tool to optimize formulations for fungal resistance and as a quality control measure for production batches.
• Product Claims & Certification: Meeting or exceeding fungal resistance requirements under ASTM D5590 supports marketing claims and compliance with client or regulatory specifications in industries such as architectural, marine, and protective coatings.
• Comparative Testing: This standard is beneficial for benchmarking new and existing products against competitor coatings or legacy formulations to ensure improved or equivalent antifungal performance.
• Environmental Testing: Laboratories use this test as part of broader environmental durability assessments, particularly for coatings destined for humid or tropical climates with elevated mold risk.

Related Standards

For comprehensive evaluation of coating performance and resistance to microbial growth, the following related ASTM standards and practices are commonly referenced alongside ASTM D5590:

• ASTM D3273: Resistance to growth of mold on the surface of interior coatings in an environmental chamber.
• ASTM D3456: Practice for exterior exposure tests for susceptibility of paint films to microbiological attack.
• ASTM G21: Practice for determining resistance of synthetic polymeric materials to fungi.
• ASTM D4708: Preparation of uniform free films of organic coatings.
• ASTM D4587 / D6695: Accelerated weathering and exposure test methods for paint and related coatings.
• ASTM D1005 / D6132: Methods for measuring dry film thickness.

Keywords: fungal resistance, paint films, coatings, agar plate assay, mildew, mold, comparative testing, ASTM D5590, accelerated testing, antifungal coatings.

By implementing ASTM D5590-17(2021), organizations gain a rigorous, comparative method for screening and substantiating the antifungal properties of paints and coatings, ultimately supporting enhanced durability and customer satisfaction in a wide range of applications.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D5590 − 17 (Reapproved 2021)
Standard Test Method for
Determining the Resistance of Paint Films and Related
Coatings to Fungal Defacement by Accelerated Four-Week
Agar Plate Assay
This standard is issued under the fixed designation D5590; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D4708 Practice for Preparation of Uniform Free Films of
Organic Coatings
1.1 This test method covers an accelerated method for
D6132 TestMethodforNondestructiveMeasurementofDry
determining the relative resistance of two or more paints or
Film Thickness of Applied Organic Coatings Using an
coating films to fungal growth.
Ultrasonic Coating Thickness Gage
1.2 The values stated in SI units are to be regarded as the
D6695 Practice for Xenon-Arc Exposures of Paint and
standard. The values given in parentheses are for information
Related Coatings
only.
G21 Practice for Determining Resistance of Synthetic Poly-
1.3 This standard does not purport to address all of the
meric Materials to Fungi
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3. Summary of Test Method
priate safety, health, and environmental practices and deter-
3.1 This test method outlines a procedure to (1) prepare a
mine the applicability of regulatory limitations prior to use.
suitable specimen for testing, (2) inoculate the specimen with
1.4 This international standard was developed in accor-
the proper fungal species, (3) expose the inoculated samples
dance with internationally recognized principles on standard-
under the appropriate conditions for growth, and (4) provide a
ization established in the Decision on Principles for the
schedule and guidelines for visual growth ratings. This test
Development of International Standards, Guides and Recom-
method is not designed to include all the necessary procedures
mendations issued by the World Trade Organization Technical
to maintain the proper microbiological techniques required to
Barriers to Trade (TBT) Committee.
provide the most accurate results.
2. Referenced Documents
4. Significance and Use
2.1 ASTM Standards:
4.1 Defacement of paint and coating films by fungal growth
D1005 Test Method for Measurement of Dry-Film Thick-
(mold, mildew) is a common phenomenon, and defacement by
ness of Organic Coatings Using Micrometers
algal growth can also occur under certain conditions. It is
D3273 TestMethodforResistancetoGrowthofMoldonthe
generally known that differences in the environment, lighting,
Surface of Interior Coatings in an Environmental Cham-
temperature, humidity, substrate pH, and other factors in
ber
addition to the coating composition affect the susceptibility of
D3456 Practice for Determining by Exterior Exposure Tests
a given painted surface. This test method attempts to provide a
theSusceptibilityofPaintFilmstoMicrobiologicalAttack
meanstocomparativelyevaluatedifferentcoatingformulations
D4587 Practice for Fluorescent UV-Condensation Expo-
for their relative performance under a given set of conditions.
sures of Paint and Related Coatings
It does not imply that a coating that resists growth under these
conditions will necessarily resist growth in the actual applica-
tion. The method is not intended to simulate or replace indoor
This test method is under the jurisdiction of ASTM Committee D01 on Paint
or outdoor exposure of paint films or related coatings.
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.28 on Biodeterioration.
NOTE 1—It is hoped that a ranking of relative performance would be
Current edition approved Nov. 1, 2021. Published November 2021. Originally
similartothatrankedfromoutdoorexposures.Paintdesignatedforservice
approved in 1994. Last previous edition approved in 2017 as D5590 – 17. DOI:
in exterior conditions should be pre-conditioned by laboratory accelerated
10.1520/D5590-17R21.
weathering prior to exposure to fungi. All pre-conditioning must be
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
detailed in the final report. This test method however, should not be used
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on as a replacement for exterior exposure (that is, Practice D3456) since
the ASTM website. many other factors, only a few of which are listed will affect those results.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5590 − 17 (2021)
4.2 Familiarity with microbiological techniques is required. Society, where such specifications are available. Other grades
This test method should not be used by persons without at least may be used, provided they are first ascertained to be of
basic microbiological training. sufficiently high purity to permit use without decreasing the
accuracy of the determination.
5. Apparatus and Materials
6.2 Purity of Water—Unless otherwise indicated, references
5.1 Balance, capable of weighing to 0.10 g.
to water are understood to mean distilled water or water of
equal or higher purity.
5.2 Incubator, or other device capable of maintaining a
constant temperature between 25 and 30°C, relative humidity
6.3 PDAor MaltAgar plates can be purchased prepared, or
of ≥85 %.
the PDAand MaltAgar powder can be purchased and prepared
according to the instructions using standard microbiological
5.3 Refrigerator, or other device capable of maintaining a
techniques and equipment.
temperature of 4 6 2°C.
5.4 Petri Dishes, 100 by 15 mm (3.9 by 0.6 in.).
7. Preparation of the Fungal Spore Inocula
5.5 Autoclave, capable of producing 103 kPa (15 psi) of
7.1 Fungal Cultures—Use the following test fungi in pre-
5,6,7,8
steam pressure at 121°C and maintaining it for a minimum of
paring the inocula:
15 min. An autoclave is not necessary if pre-prepared media
5 6
Fungi ATCC # NRRL
plates are used.
Aspergillus niger 6275 334
Penicillium pinophilum 11797 3647
1 3
5.6 Paint Brush, coarse bristle, 12 to 19 mm ( ⁄2 to ⁄4 in.). 8
Aureobasidium pullulans 9348 62100
5.7 Substrate, Filter Paper (Glass fiber, Grade 391, 4.2 cm
NOTE 2—These organisms were selected based on the historical data
(1.65 in.)) or drawdown paper (unlaquered chart paper 216 by from use in Test Method D3273. Other organisms may be of specific
interest for certain applications or geographical areas. Such other pure
280 mm (8.5 by 11 in.), cut into ten 216 by 28-mm (8.5 by
cultures, or isolated wild strains, may be used as agreed upon by the
1.1-in.) strips.
parties involved.
5.8 Atomizer or Chromatography Sprayer.
7.2 Maintain stock cultures of these fungi separately on an
5.9 Sterile Glass Rods, Forceps, 250-mL Glass Erlenmeyer appropriate medium such as potato dextrose agar plates or
Flasks, Test Tubes, and other routine microbiological equip- slants. The stock culture may be kept for not more than 4
ment. months at approximately 3 to 10°C (37 to 50°F). Subculture
individual fungi onto slants or plates 7 to 20 days at 28 to 30°C
5.10 Potato Dextrose Agar (PDA) or Malt Agar.
(82 to 86°F) prior to each experiment, and use these subcul-
5.11 Nutrient-Salts Agar (as found in Practice G21).
tures in preparing the spore suspension.
5.11.1 Preparethismediumbydissolvingin1Lofwaterthe
7.3 Prepare a spore suspension of each of the test fungi by
designated amounts of the following reagents:
pouring into one subculture of each fungus a sterile 10-mL
Monopotassium phosphate (KH PO ) 0.7 g
2 4
portion of water, or of a sterile solution containing 0.05 g/L of
Mangnesium sulfate (MgSO ·7H O) 0.7 g
4 2
a nontoxic wetting agent such as sodium dioctylsulfosuccinate.
Ammonium nitrate (NH NO ) 1.0 g
4 3
Sodium chloride (NaCL) 0.005 g
Swirl or gently agitate the slant or plate to loosen the spores.
Ferrous sulfate (FeSO ·7H O) 0.002 g
4 2
Carefully aspirate the water and spore suspension with a sterile
Zinc sulfate (ZnSO ·7H O) 0.002 g
4 2
Manganese sulfate (MnSO ·H O) 0.001 g Pasteur pipet (trying to avoid obtaining mycelia).
4 2
Agar 15.0 g
7.4 Filter the shaken or ground suspension through a thin
Dipotassium phosphate (K HPO ) 0.7 g
2 4
layer of sterile glass wool in a glass funnel into a sterile flask
5.11.2 Sterilize the test medium by autoclaving at 121°C
in order to remove mycelial fragments.
(250°F) for 20 min.Adjust the pH of the medium so that after
sterilization the pH is between 6.0 and 6.5. 7.5 Dilute the spores suspension with sterile nutrient salts
solutionsuchthattheresultantsporesuspensioncontains0.8to
5.12 Nutrient-Salts Solution, (see 5.11 without agar).
1.2 by 10 spores/mL as determined with a counting chamber.
5.13 Counting Chamber (Hemocytometer).
7.6 Repeat this operation for each organism used in the test.
5.14 Glass Wool.
The A. pullulans spores should be maintained separately and
5.15 Laboratory Accelerated Weathering and Leaching
Equipment, if used.
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the American Chemical Society, see Analar Standards for Laboratory
6. Reagents and Materials
Chemicals, BDH Ltd., Poole, Dorset, U.K., an
...