ASTM D3274 - 09(2013)

    Standard Test Method for Evaluating Degree of Surface Disfigurement of Paint Films by Fungal or Algal Growth, or Soil and Dirt Accumulation

    Active Standard ASTM D3274 | Developed by Subcommittee: D01.28

    Book of Standards Volume: 06.01


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    Significance and Use

    4.1 The growth of fungi in and on the surface of paint films represents a major cause of discoloration or disfigurement of painted surfaces. Because of their dark pigmentation, it is frequently difficult to distinguish fungi from dirt or soil particles.

    4.2 Use of Pictorial Standards:

    4.2.1 The pictorial references that are part of this test method are for illustration purposes and may be used for visual comparisons.

    4.2.2 The diagrams represent an idealized schematic of various growth levels on paint films. they are intended as a representation only, but will serve as a useful guideline to establish amount and type of growth.

    4.2.3 The diagrams represented in Fig. 1 are not derived from a linear scale. The scale is intended to provide for more discrimination at the earlier stages of fungal or algal growth. It is at these levels that greater discernment is necessary.

    4.2.4 Comparisons made on dark colored substrates will be much more difficult, and will therefore require much more care and attention. It must be noted that because it is difficult to distinguish mild fungal or algal growth on the very dark substrates, there may be a tendency to under-rate those specimens.

    1. Scope

    1.1 Fungal growth, frequently referred to as mildew in the paint industry, causes defacement of paint film exposed outdoors. The visual rating of paint surface disfigurement due to fungal or algal attack is required in order to compare the performance of different coatings.

    1.2 This method of rating mildew evaluation is intended to be used on exterior exposed paint films. This method may be used to rate interior fungal or algal growth, but it should be noted that the growth patterns on interior surfaces are different than exterior due to the lack of weathering influences. It is primarily intended for test specimens, but can also be sued for rating mildew growth on larger structures such as entire houses. If this is used for large areas, the project should be broken down into smaller sections.

    1.3 This method is intended for field use for the macro rating of surface disfigurement only. The visual scales are meant to be used by the unaided eye to rate algal, fungal, or dirt disfigurement on larger surface areas such as test panels, siding boards, or entire buildings. Techniques are included for the differentiation of soil and dirt.

    1.4 Fungi will grow on most paint films exposed outdoors that are located in conditions favorable to growth. Test procedures such as Practices D1006, D3456, and G7 are available describing natural exposure tests that can be used to expose paint films, in order to create fungal or algal growth.

    1.5 The pictorial references available for use with this test method provide a numerical basis for rating the degree of fungal or algal growth on paint films.

    1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D1006 Practice for Conducting Exterior Exposure Tests of Paints on Wood

    D3456 Practice for Determining by Exterior Exposure Tests the Susceptibility of Paint Films to Microbiological Attack

    D4610 Guide for Determining the Presence of and Removing Microbial (Fungal or Algal) Growth on Paint and Related Coatings

    G7 Practice for Atmospheric Environmental Exposure Testing of Nonmetallic Materials


    ICS Code

    ICS Number Code 87.040 (Paints and varnishes)

    UNSPSC Code

    UNSPSC Code 46181533(Protective coats)


    DOI: 10.1520/D3274

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