by aseptic addition of one ml of a fungal spore suspension onto the 

 paint film and the agar surface. Incubation was carried out in an 

 environmental chamber set at 30 to 32 C with a relative humidity of 

 approximately 85%. The culture plates were incubated upside down for 14 

 days before observing the paint films. All tests were run at least in 

 duplicate, and the organotin resins were compared with the original 

 resins. 



Table 2. Composition of Culture Media 



Chemical Compound 



Amount (g) 



Sodium nitrate 



3.0 



Dipotassium hydrogen phosphate 



1.0 



Magnesium sulfate 



0.25 



Potassium chloride 



0.25 



Sucrose 



30.0 



Agar 



10.0 



Distilled water (to make 1,000 ml) 



- 



Gross examination of the paint film revealed the level of fungal 

 growth. Zones of growth inhibition were also examined, measured, and 

 recorded. The plates were then examined under a light microscope at 40X 

 magnification. The photographs (Figures 1 to 3) in ASTM D3274-73T [16] 

 were used to distinguish spores (spherical reproductive bodies, gray to 

 black, occurring singly or in clusters) from dirt particles and to deter- 

 mine the amount of growth of hyphae (thread or filamentous structures, 

 gray to black, making up the mycelium or vegetative form of fungi). 

 From these examinations, one of the following ratings depicted in Figure 

 2 was assigned to each test plate: 



5 - No growth on resin film; large zone of inhibition on agar. 



4 - No growth on resin film; growth on agar up to edge of film. 



3 - Sparse mycelial growth on resin film; no production of new 

 spores. 



2 - Moderate mycelial growth on resin film; slight production of 

 new spores. 



1 - Heavy mycelial growth on resin film; heavy production of new 

 spores. 



- Little distinction between growths on resin film and on agar. 



