THREE PRIME FACTORS IN SUCCESSFUL PACKAGING closures and styles of finishes com- monly manufactured. A number of types were obsoleted and standards set up which have been well ac- cepted by the glass container manu- facturers and the trade. This standardization has enabled the glass manufacturers to work to closer tolerances, and permits a user to buy either closures or containers from two or more sources of supply and be sure that the closures will fit the containers of any manufacturer, or vice versa. The Standardization Committee of G.C.M.I. is still quite active in improving present finishes and approving suggested changes. Screw caps consist of two com- ponent parts, namely, the cap itself and the liner. The caps may be made from metal or from synthetic molding materials. Before the war, metal caps were produced of tinplate, aluminum or terneplate. Some closures were made from brass or nickel-plated brass, though these were not con- sidered "standard" closures f•r the general industry. They do find ex- tensive use in the Toiletties Indus- try. Terneplate consists of steel coated with a lead alloy, and has not been used generally for cosmetic or food purposes, due to the high lead content. Owing to the scarcity of tin during the war, it was necessary that its use be curtailed conse- quently, only highly essential items were permitted the use of tinplate. The closures were produced from black iron and bonderized black iron. Clostires made from sub- stitute materials are subject to rust- ing when exposed to conditions of high humidity or corrosive prepara- tions. The protective coatings, either oleoresinous or synthetic, do not sufficiently protect black iron or bonderized blackplate from rust. Frequently under-film corrosion de- velops, in which the rust develops beneath the protective coating, since moisture-vapor penetrates through the coating. The protective coat- ings adhere better to the bonderized plate than to the plain black iron. It must also be remembered that during the war period raw materials for protective finishes were scarce, and many substitutions had to be made which did lower the quality of the protective finishes. Tinplate, while it will rust under adverse conditions, has stood up very well in general use. During the war, the electro-tinning of plate was developed, whereas, formerly,' the hot-dip practice was used. In this latter method, approximately 11/4 to 11/2 lbs. of tin were applied to a base box of steel plate. By the electro-tinning method, equivalent rust protection can be developed by the use of 8/4 lb. of tin per base box, or somewhat less. When tin again becomes available, electro-tinplate will be u. sed generally for screw caps. Prior to the war, a sizable quan- tity of caps was produced from aluminum, although the cost was somewhat greater than tin. Should aluminum be equivalent in price to tinplate, it will find considerable use in the post-war period. Aluminum will be attacked by alkaline prod- ucts and by certain inorganic salts,

10 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS though the corrosion products of aluminum are generally white in color and not as unsightly as the brown iron rust which develops on black iron or sometimes on tinplate. Protective coatings for metal plate are used both on the inside and outside of the caps. For aque- ous products, an oleoresinous type is generally used, though synthetic coatings are available which have good alcohol, acid and alkaline re- sistance. Similar coatings may be applied on the outside of the metal, or the metal base may be litho- graphed and, if lithographed, is pro- tected by a clear coating over the lithography. Very attractive colors varying from black through the solid colors and pastel shades to white can be used. In the manufacture of metal caps, the protective coatings are i•pplied to the plate in the fiat, and from the decorated plate blanks, generally of the shape of a stiff straw hat, are first produced. These blanks are then put into thread roll- ing machines which turn the bead, form the thread, and form the knurl if knurled caps are being produced. Knurling increases the finger hold and aids in the removal of closures. The knurling tools tend to rupture the coating and form focal points which can develop corrosion, though on the inside of the cap the exposed portions are generally protected by the liner and under normal storage the outside does not develop rust. It is interesting to note that the protective coatings and decorations are applied to the fiat sheet. The sidewall of the blank in which the threads are formed is subject to some stretch during the punching opera- tion. This stretches the' coating, and the coating is then further stretched when the threads are formed in the closure. It is really remarkable that, under this drastic treatment, protective coatings have been formulated which will take the stretch, remain properly adhered to the metal, and afford additional protection against rust. Metal caps are produced in sizes from 15 to 120 mm. The smaller sizes are more difficult to make and control to accurate dimensions, though closures from 18 mm. on up are quite satisfactory. Molded closures are relatively newcomers in the closure field, being about twenty years old. They are produced from compounded syn- thetic resins, and are of two types, namely, the thermoserring or those made from thermoplastic materials. Molded closures are produced to accurate dimensions, and these' di- mensions depend upon the accuracy to which the molds themselves are made, for the molding materials faithfully reproduce the various contours of both the cavities and force plugs which form the outside and the inside portion of caps. All molding materials shrink to some degree on cooling however, allow- ances for this are made in the manu- facture of the tools, so that accurate caps are produced. The'most generally used thermo- serring molding materill is of the phenol formaldehyde resin type.