The growth of fungi and algae 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 and algae from soil or dirt particles. The use of magnification of as much as 100× affords easy distinguishability among fungal spores, fungal mycelia, algae, and dirt and is recommended in cases where such difficulty is apparent.

Dirt accumulation observed on specimens can occur more readily with coatings formulated at lower pigment volume concentration or those containing softer resins.

Use of Photographic Standards:

³

4.3.1 The photographic reference standards that are part of this test method are for illustration purposes and should be used for visual comparisons.

4.3.2 The photographic standards illustrated in Fig. 4 rate the disfigurement of paint films from 0 to 8. A rating of 10 would indicate a film totally absent of disfigurement by particulate matter.

4.3.3 The ratings used in this standard more closely match a nonlinear scale.

FIG. 4 Disfigurement Ratings