the normal saturation expected in tobacco warehouses. These tobacco samples 

 were tested in the Eastern Regional Research Laboratory of the Department of 

 Agriculture by B. A. Brice, of the Bureau of Agricultural and Industrial Chemis- 

 try. In a report dated February 10, 1948, he states in conclusion: 



Since the methyl ethyl ketone and acetone contents of the treated samples were the same as 

 those of the untreated samples (controls), it can safely be concluded that the treated samples 

 (R and B) did not retain any methyl ethyl ketone or acetone volatilized from the sealing 

 compounds. 



Smoke tests of cigarettes made from the treated and from the untreated tobacco 

 showed no differences. Samples of exposed tobacco were examined by the 

 Tobacco Branch (PMA), and were found to contain no foreign odor. All to- 

 baccos tested were of cigarette. and smoking types grown in the flue-cured area. 

 It is believed that tobacco generally would react in a similar manner; however, 

 cigar types have not been specifically tested. 



Results of Tests 



On the basis of these findings, plastic was applied to commercial warehouses at 

 Charleston, S. C, and Norfolk, Va. Fumigation of these sealed sections has been 

 entirely satisfactory and has shown that this method of sealing meets all the 

 requirements of this type of work. 



The manufacturers of plastic film have already made changes and improve- 

 ments in the basic Navy formula. The development of materials adapted to 

 specialized usages in industry has gone forward with the demand, and further 

 improvements can be expected in this field. There is a possibility that a product 

 with a controlled degree of adhesion will be placed on the market in the near 

 future. Such a product should be an improvement from the standpoint of 

 tobacco-fumigation work. 



The Department of Agriculture, as a result of the various tests and commercial 

 applications made, finds vinylite plastic (sprayable) adaptable for use in sealing 

 closed-type tobacco-storage warehouses. 



MATERIALS 



Coating— Webbing — Adhesive 



Vinylite plastic film is a viscous liquid which comes from the manufacturer in 

 sprayable form ready to use. It is shipped in metal containers, or drums, as shown 

 in figure 5. This is the basic material used in plastic spraying and is complete in 

 itself when applied on relatively solid surfaces. 



In order to form a foundation for the plastic film on voids, holes, and cracks that 

 are wider than % inch, it is necessary to add to this basic solution a material 

 known as webbing agent. This webbing compound is added in proportions of 

 approximately 1 part to 3 or 4 parts of the coating solution. A sufficient quantity 

 of the combination should be prepared for each day's operation. The method of 

 adding webbing compound is illustrated in figure 7, page 12. 



In cases in which the webbing solution had been mixed for several days it was 

 found that a separation of the two ingredients had occurred. This incompata- 

 bility can be overcome by agitating the mixture thoroughly at the beginning of 

 each operation and again on succeeding days if necessary. 



During cold weather proportionately more webbing agent is needed in the 

 mixture than when higher temperatures prevail. It is advisable to start with 

 a normal mixture and add enough of the webbing agent to obtain the desired 

 solution. With each addition the mixture should be thoroughly stirred or agi- 

 tated. As a recent development, a complete webbing solution already mixed and 



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