by the manufacturer in the basic product. It should always be a part of the 

 solution when it is applied on exteriors or in exposed locations. If a pigmented 

 material is purchased, it is desirable, but not essential, to obtain some clear plastic 

 film for use in mixing the webbing compound. 



Thinner or Retarder for Plastic Solution 



Weather conditions affect the application of these materials. When plastic 

 coating is applied during cold weather, it is important that a thinner be used only 

 where absolutely necessary. Evaporation of the solvents is slowed down at low 

 temperatures and additional thinner tends to retard this action further. Excessive 

 thinner tends to allow the materials to run and the resulting thickness of the 

 application varies. It is, therefore, desirable to agitate the material wherever 

 possible in order to avoid the use of a thinner. Whenever plastic is being agitated, 

 the pressure pot should be tightly closed and, if possible, the operation should be 

 performed in the open air. 



Figure 7. — Open spray-pressure pot equipped with agitator and air motor. 



Plastic coating compound has a tendency to become more viscous with age. 

 Where drums have been stored for a considerable time this excessive viscosity may 

 be found. If the solution is too thick for spraying, agitation will remedy this 

 condition in most cases. A pressure pot, equipped with agitator, used in this 

 operation is shown in figure 6. Where a thinner is required, it should be methyl 

 ethyl ketone, acetone, or a product recommended by the maker of the basic plastic 

 solution. 



At extremely high temperatures, above 90 F., the addition of a retarder is rec- 

 ommended by the Navy. Methyl iso-butyl ketone, methyl hexyl ketone, and tolu- 

 ene have been used and are satisfactory in slowing down the drying process. 

 There is little likelihood that a condition will be found in which the addition of 

 a retarder is required. In most instances the adjustment of the spray-gun nozzle 

 will allow a sufficiently wet application that will flow properly and form an even 



10 



