FLEXIBLE PACKS 4• packaging". It is not proposed to deal with moulded plastic containers, and only to a limited extent with single plies of plastic material, e.g., P.V.C. tubing. It is the purpose of this paper to deal mainly with packages which can be formed from webs of composite or laminated materials. FIELD OF APPLICATION The field of application of such packages is necessarily limited. Cosmetics, in general, are in the luxury class, and the container plays a very important part in the general sales appeal. Most cosmetic containers have also to be designed for re-closure as the contents are usually used over a period. Consequently, the present field for flexible containers is largely confined to "one shot" units, e.g., liquid shampoo, face packs, face tissues, etc. The basic requirements of these packs, however, are the same as for the re-use pack---they must be attractive and give the impression of quality they must afford reasonable protection against the passage of moisture, scent, and, in many cases, essential ingredients which are incorporated in the product must not migrate into the material. At the same time, the container must be sufficiently robust to contain the product and to stand up to reasonable handling in transit and subsequent distribution. EFFECT OF PRODUCT REQUIREMENTS ON CHOICE OF MATERIAL Each product has to be considered entirely on its merits. It does not follow that if a particular sachet material is suitable for a given product it will necessarily be entirely suitable for a similar product with a different formulation. There are, for instance, variations in viscosity, and as a result a material which is suitable for a cream or concentrated viscous shampoo would not necessarily be suitable for a more free-flowing product. Again, a transparent sachet may be perfectly suitable for a product of a certain colour, whereas a similar product in a different colour may be affected by light and consequently a transparent pack is undesirable. Certain products are affected by having access to oxygen, and chemical changes can take place over a period. On the other hand, it is not always necessary that the material used should be a complete barrier to the perfume used in its formulation as a detectable scented odour can be an asset to sales if the transmission of odour is not sufficient to lose strength over a period or to affect other goods with which the packs may come into contact. For this reason laminations play such a big part in this type of packaging as it is possible to obtain different characteristics by using a variety of materials. DEVELOPMENT OF UNIT LIQUID PACK The unit liquid pack, particularly for shampoo, was originally based on

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the use of transparent materials for obvious reasons. Previously, all liquid shampoos had been sold in bottles but there had been, for many years, an appreciable demand for "unit" portion shampoo in powder form packed in envelopes. It was desirable, therefore, that liquid sachets should be readily distinguishable from powder sachets consequently, a transparent lamination which showed the contents was the first requirement. Once the public had become used to the idea of liquids being packed in sachet form, the necessity of seeing the product became less important and, in some cases, undesirable. Generally speaking, clear coloured liquids could be displayed attractively in transparent material, but opaque cream shampoos were less attractive and, in some cases, called for materials which gave the necessary protection, and display value, without depending on the appearance of the product for its sales appeal. It must be remembered that the sachet was introduced originally to supplement and encourage the sale of a particular shampoo in the traditional package, i.e., a bottle. The idea behind the introduction of the unit pack was that the public would be prepared to try a new produce more readily if it were available at an attractive price in the form of a single use pack. If they liked the new product, they would then buy a bottle containing sufficient of the product for several applications. This, no doubt, proved to be the case with products first introduced in this way, but it soon became apparent that the convenience of the unit packs was such as to outweigh the apparent economy of buying in the bottle. The reasons for public acceptance of a particular form of pack are always extremely difficult to assess, but it is fairly certain that a larger number of people bought "single shot" shampoo packs in liquid form than had either previously bought powder shampoo in envelopes, and had not previously been in the habit of buying bottles. The fact that a large proportion of the public buys on a restricted weekly budget makes the availability of the cheap "single use" pack extremely attractive. A large percentage of the buying public is also very fickle as far as particular brands of cosmetics are concerned, and will readily try a new product if it is attractively presented, and advertised, and if available at a price which suits their budget. }V[ATERIALS The first material which was used successfully for liquid shampoo packing, other than heavy P.V.C. tubing, was a lamination of cellulose acetate to Pliofilm by means of an adhesive which was designed to remain permanently tacky. A great deal of experimental work was necessary in order to attempt to produce an improved lamination, and to use alternative materials, but so