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

FLEXIBLE PACKS 45 far none have been produced which show an all-round improvement. As far as the inner ply is concerned, this has to provide a reasonable barrier to moisture, and to the penetration of the ingredients incorporated in the product. From the available plastic material, Pliofilm has proved to combine the necessary characteristics, coupled with its suitability for heat sealing on sachet forming and filling machines. This characteristic is referred to more fully when dealing with heat sealing problems. The use of cellulose acetate as the outer ply was determined mainly on account of its dimensional stability, coupled with clarity and suitability for printing. Various grades of regenerated cellulose film have been tested from time to time as an alternative to cellulose acetate but the dimensional variation has been such that the tendency to delamination is greatly in- creased, and on the whole it has not been considered a satisfactory alternative. DEVELOPMENT OF Iq'ON-TRANSPARENT PACKS As mentioned earlier, transparency is not always desirable consequently a demand developed for an opaque pack. The first material to be used was a lamination of paper and Phofilm, which had the advantage of being opaque, and was rather cheaper than the acetate Pliofilm lamination. This make-up was found to have severe limitations. The moisture loss through the lamination was considerable, and the strength of the sachet, even when sealed under the best conditions, was marginal. There was also an increased tendency of moisture loss. To overcome this, a ply of aluminium foil was introduced between the paper and the Pliofilm, producing a triple lamination--paper/foil/Pliofilm. This materiM was an extremely good barrier to moisture, and also made up into a much stronger sachet than paper Pliofilm. There were, however, still some difficulties notably a tendency for the aluminium foil to delaminate from the Pliofilm when the sachets were stored for any length of time, particularly at elevated temperatures. This was due to ingredients of the shampoo getting through the Pliofilm and weakening the bond. This problem is far more acute when an impermeable barrier such as aluminium foil is next to the Pliofilm, as the latter becomes saturated, causing the film to swell and become detached from the foil. Paper/foil/ Pliofilm is still used for certain products, mainly rather viscous creams e.g., face packs. The next development was foil/paper/Pliofilm, that is, with paper sandwiched between the film and the foil. When made up this produced a sachet with good strength characteristics and also allowed the brilliant