14 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS is adequately lacquered, does it mean that the lacquer is, in fact, not suitable for the product if the film lifts after filling ? THE LECTURER: Very often the lacquer itself is eminently suitable for the product. Usually it is defective application, e.g. heat treatment of the container, or lubricant residues which cause loss of adhesion. Particularly traces of lubricants, which in the dry state give perfect results, may cause the films to fail very drastically after being in contact with the product for some little time. MR. A. FOSTER: Then the product does have some kind of effect on the lacquer ? THE LECTURER: If everything else had been equal and if some permea- tion had taken place, it would not have happened if there had not been some defect in the processing of the containers. The product does obviously have some effect, but this would have been cancelled out if the processing had been correct. MR. A. SMITH: The lecturer makes the point that in order to overcome the difficulty of lacquering at the nozzle of a collapsible tube, a plastic nozzle may be used. This approach, however, does not seem to have found universal use. Does the elaborate type of plastic nozzle used have a cost effect on the finished tube ? THE LECTURER: There is now a greater tendency to use plastic nozzles and I think they will come into more general use. Polypropylene and high density polythene are often used. I do not consider, particularly with the envisaged usage, that in the long run the cost factor will be important or make much difference. MR. A. SMITH: IS there an additional problem of sealing the nozzle ? THE LECTURER: No. There is a standard test for assessing the tightness of the nozzle. This is an engineering problem and not insuperable. MR. R. CLARK: We have experienced product spoilage arising from corrosion at the neck of the tube. A fresh annealing process did improve the tubes but there was still product spoilage. The metal on the shoulder and body of the tubes differed. Lacquering was resorted to and because of the cost of varnishing, the tubes were more expensive. To cancel out variables, standard lacquering had to be resorted to presumably more and improved efficient production lines reduce the unit cost of the tube, but does it benefit the buyer ? THE LECTURER: I never discuss prices. MR. R. K. WALMSLEY: The degree of lacquer curing is very important. Could you elaborate how we can establish the degree of the curing ?

PRODUCTION AND PROPERTIES OF GLASS CONTAINERS 15 Tu• LECTURER: I presume you wish me to refer to Araldites and Epikotes in particular. There is a curing range below which a lacquer is under-cured and above which it is over-cured or burnt. The simplest way of testing this is by colour, and our Lacquering Section provides a series of "swatches" which show the limits of the colour of the final film. There is, however, another lengthy and time-consuming way. The film is sprayed with mixed solvents, left to absorb them, swell and then wiped off. The more a lacquer is cured the greater its resistance to mixed solvents, chloroform, methylated spirits, etc., depending on the type of resin used. The colour of the film is, however, a very good guide. MR. R. K. WALMSLE¾: With reference to plastic nozzles, do you not have a problem of protecting an uncut edge somewhere within the seal ? How do you protect the cut edge of the tube which is unlacquered, from the product ? T• L•CTURER: The raw edge of the metal does not come into contact with the product at all and fits into a flange device in the plastic nozzle. The product thus cannot come into contact with the cut edges. MR. R. K. WALMSLE¾: IS the nozzle applied after lacquering ? TUE LECXtJR•R: Yes, and internal waxing is applied after the plastic nozzle is fitted. For that reason we are experimenting with polypropylene because of the temperatures involved in the waxing operation. PRODUCTION AND PROPERTIES OF GLASS CONTAINERS C. TARRANT* Presented at the Symposium on "Packaging in the Cosmetic Industry", organised by the Society at Harrogate, Yorks., on $th July 1961. The historical origin, composition, chemical durability, surface treatment and flaking of glass are discussed. The protection of light sensitive products is also dealt with. •DEFINITION G•-Ass IS so commonplace a part of everyday experience that a definition is almost unnecessary, yet the term has been applied to such a variety of substances that some preliminary indication should be given as to the type of substance the properties of which are to be considered here. * Key Glass Works, Ltd, London S.E.14.