Pigment may be added to the plastic solution, thus giving it resistance to 

 weathering and the direct rays of the sun. Pigmented plastic is shown in figure 3. 

 When applied either with or without pigment, plastic sealing is less unsighdy 

 than sealing with mineral asphalt and paper. 



Development of OS-3602 by the Navy 



During the war period the Bureau of Ordnance of the Department of the Navy 

 developed a vinylite plastic film known as OS-3602. The development of this 

 plastic has made possible a complete revision of the methods and materials pre- 

 viously used in sealing storage warehouses. All the topside ordnance units, as 

 well as some of the machinery units in vessels of the Reserve Fleet, were sealed by 

 the Navy with strippable plastic to protect them from rust, corrosion, and ex- 

 posure to the elements and to preserve them in readiness for immediate reactiva- 

 tion. A majority of these plastic covers were later replaced with permanent-type 

 metal enclosures. 



Naval Bureau of Ordnance publication OP 1485, Instructions for Application 

 of Strippable Coating (Spray Type) (OS-3602), dated April 2, 1945, gives a 

 detailed description of the manner in which the Navy handled its plastic program. 

 Although the problems discussed are different from those found in the tobacco 

 industry, the publication is of value in training employees engaged in this work. 



Navy specifications call for an application of not less than 0.040 inch of film. 

 As a result of this method, the Navy obtained a satisfactory moisture barrier for a 

 period up to 3 years, during which time the barrier or plastic was exposed to 

 average weather conditions but received routine maintenance amounting to a 

 semiannual reworking, or patching, and recoating as found necessary. 



Army Specification 



The Artillery Division of the Department of the Army also set up production- 

 line usage of plastic. Later it added a top coat of coal tar and bitumastic-type 

 materials. Department of the Army specification dated October 29, 1946, and 

 identified as "AXS-1756 — Compound, Protective, Strippable (Sprayable), covers 

 the material currendy used by that Department. 



Experimental Work by Department of Agriculture 



The Tobacco Branch of the Production and Marketing Administration, in its 

 administration of the tobacco-loan programs, for the Commodity Credit Corpo- 

 ration, is required to see that stored collateral is properly protected. 4 Investiga- 

 tion revealed that Navy formula OS-3602 was probably adaptable to the sealing 

 of storage warehouses. 



Experiments were conducted at the Army Base warehouses at Norfolk, Va., on 

 December 11 and 12, 1947, in an effort to test the application of plastic under 



4 Pursuant to section 8 of the Stabilization Act of 1942, as amended (October 2, 1942), 56 

 Stat. 767, as amended June 30, 1944, 58 Stat. 632, and as amended June 30, 1945, 50 U. S. C. 

 App. (sec. 968), Commodity Credit Corporation made loans available on 1946 and 1947 flue- 

 cured tobacco crops. As a result of these programs approximately 265,000 hogsheads of flue- 

 cured tobacco were stored as collateral for nonrecourse loans. A comprehensive insect-control 

 program was considered essential to protect this tobacco from infestation by the tobacco moth 

 and the cigarette beetle. Joseph N. Tenhet, Head of the Stored Tobacco Insect Laboratory 

 (BE&PQ), at Richmond, Va., cooperated in the development of this program. Under it, 

 tobacco was to be fumigated if possible; otherwise it was to be sprayed with pyrethrum oil. 

 The program was carried into effect by the Flue-Cured Tobacco Cooperative Stabilization Corpo- 

 ration at Raleigh, N. C, and a major part of the information contained in this publication is 

 based on results of sealing work performed by this grower cooperative organization. 



