14 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS varnished papers are definitely attacked by essential oils or prod- ucts containing the essential oils. A wax coating applied to the varn- ished paper improves the moisture transmission characteristics, though the wax tends to hold carton dust, and the dust developed in manufac- turing operations, and may at times flake and show up as floating parti- cles on the product. Vinylire, the copolymer of vinyl acetate and vinyl chloride plasti- cized and pigmented, hak been applied to a white sulphite paper to produce an excellent facing material and has enjoyed quite general use. The Vinylire resin is dissolved by the ketones, consequently it cannot be used with nail polish or nail polish removers and is attacked by certain perfumes. Vinylire has good mois- ture-vapor transmission character- istics. During the (var period, this lining material was decidedly scarce, although it is currently available in reasonable amounts. Before the war, Panaseal was a very active competitor of Vinylire. It consists of the product Pliofilm (a rubber hydrochloride compound) mounted on white sulphite paper. This material was also soluble in the ketones and in the chlorinated hydrocarbons, as well as the hydro- carbons, and was attacked by cer- tain perfumes. It has good mois- ture-vapor transmission character- istics, and was used in jar covers for cold creams. A urea formaldehyde-alkyd resin type of varnish was applied to white sulphite paper by several concerns under the trade names Silite, White- seal and Impervite, and used as a replacement for Tinfoil, Vinylire and Panaseal during the war. The film is inclined to be somewhat brittle and does not have much stretch. It is best used with a non- resilient type of backing such as newsboard, and is used as a sub- stitute for Tinfoil in many applica- tions. The newer synthetic resins such as Saran, Polythene and Nylon will, in the future, enter the liner field. At the present time they are either too expensive, have not been pro- duced in sufficiently thin films, or have too great odor or taste trans- mission tendencies. They do have some admirable resisting character- istics, and a serious effort is being made to utilize them for the de- velopment of a more nearly uni- versal type of liner. Some concerns have used waxed pulpboard as a liner for cold creams. This is probably as cheap a light colored liner as can be obtained. Its efficiency is low and its moisture- vapor transmission characteristics also are poor. Saturatedpulpboard consists of pulpboard impregnated with a wax and oil combination. This type of liner has been used for cold creams, and is better than the waxed pulp, but is really not ideal. Quality white waxed paper consists of white sulphite paper with an application of paraffin or micro- crystalline waix. It has been used mounted on p. ulpboard or on satu- rated pulpboard, and has fair mois- ture-vapor transmission character-

THREE PRIME FACTORS IN SUCCESSFUL PACKAGING 15 istics. It is white in color, although not as efficient as Vinylire or Pana- seal mo. unted on pulpboard or newsboard. Since the liner repre- sents a very small factor in total package cost, price consideration should have very little influence on the manufacturer's selection of the liner to protect his product. Unless the liner provides maximum pro- tection for the product, it is worth- less at any price. Furthermore, while a liner may satisfactorily seal a product marketed by one manufac- turer, it does not follow that another product of similar nature (but with a slight change in formulation) will be satisfactorily sealed with the same type of liner. To obtain the most dependable liner, laboratory recom- mendations by the cap manufac- turer should be obtained and the cap manufacturer's recommendation should, in turn, be checked by the laboratory of the manufacturer who packages the merchandise. Often it is desirable to run tests for ex- tended periods of time. Screw caps should be applied to containers with a proper tightening force: With too little force, the liner may not be properly seated and leakage may result. With to• great force, the threads or top finish in metal caps may be distorted and. molded caps may be broken. Again, if the caps are too tightly applied, they may be difficult to remove, causing customer dissatisfaction. Studies conducted by the Pitts- burgh Testing Laboratory for one of the cap companies, indicated that the average housewife could exert a force on a 28 min. cap equivalent to 33 lbs. tangential, or 17.95 torque inch pounds to remove a screw finish cap. This force is therefore the maximum that should be applied, and laboratory experience has indi- cated that it is not necessary to reach this limit to produce an effec- tive seal with properly chosen liners and good glass finish. The torque inch pounds, of course, will depend upon the diameter of the cap and the number of threads per inch, and will vary from 4.75 torque inch pounds in a 15 min. cap to 95 lbs. for 120 min. caps. Waxed liners reduce the friction between the liner itself and the glass finish consequently, the caps can be applied furthee than normal, and the application of caps with such liners should be studied carefully to avoid excessive tighten- ing. As has been indicated, the liners can be attacked by various products. This is also true of glass containers. The better glass companies now pro- duce glass which is of good chemical durability. The common container glass several years ago was quite high in soda, and would cause a change in pH in a neutral product. As a matter of fact, some of the glass would show a definite alkaline reac- tion to phenol-phthalein when ar- bon dioxide-free distilled water was placed in the bottle, and the bottle then placed in a water bath and the temperature raised to 90øC. and held for one hour. The glass which showed this reaction would deft- nitely. produce flakes or spicules in water or in 50-50 alcohol and water.