The ASTM D3274 Method details a standardized rating system designed to evaluate the degree of fungal resistance of surface coatings (e.g. paint films). This method is used for tests such as the ASTM D3273. Ratings are based on the percentage of surface fungal coverage and qualitative descriptions. While this method was originally designed for field observations, it may also be applied to observations made within the laboratory.


Summary of the ASTM D3274 Rating Method

  • Fungal growth pattern is observed and determined to be either spot growth, non-uniform spread, or complete coverage.
  • The percentage of surface coverage is determined and assigned a rating of 0-10. A rating of '10' corresponds to no fungal growth while a rating of '0' requires 50% (or greater) surface coverage.

Strengths of the ASTM D3274 Rating Method

  • The rating system is straightforward and the degree of fungal resistance is determined visually.

Weaknesses of the ASTM D3274 Rating Method

  • Dark surface coatings add difficulty in making growth comparisons and usually require added attention to avoid under-rating growth.
  • The rating system is subjective and test results can therefore vary.

Microchem Laboratory hopes that this ASTM D3274 test method resource has been helpful. If your company is interested in testing the resistance of a surface or coating to fungal attack or defacement, consider ASTM D3273 or ASTM G-21.

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