HYGIENIC MANUFACTURE AND PRESERVATION 793 able for the maintenance of plant hygiene. In general, chemical sterilants cannot be incorporated as ingredients of products as they necessarily have a high degree of intrinsic chemical and biological reactivity they are liable to alter the product characteristics to a marked extent or to elicit adverse cutaneous reactions. However, just as a chemical disinfectant will effectively sterilize clean surfaces of equipment, so a small percentage of a bactericide or fungicide may exert a sterilizing action in a cosmetic product which has been prepared in a clean and hygienic manner. The possibility of using preservatives to achieve self-sterilizing properties in cosmetics is dealt with in Appendix B the principle, in brief, is that the preservative should not be employed to achieve sterility at the time of manufacture (which should depend on other measures) but should be aimed at the destruction of limited numbers of contaminants entering the product at a later stage. 2.7 Flaming For microbiological test procedures, including the taking of samples in the production area, a rapid method of sterilizing hard surfaces of small pieces of equipment is often needed, e.g. temporarily-opened necks of bottles and also wire loops used for inoculating culture media. Direct heat- ing in an open flame is employed and should be carried out thoroughly, in close proximity to the point where the flamed equipment will be used quick passage through the flame gives reassurance but not sterility. Metal instru- ments (scissors, etc.) may be sterilized by swabbing with alcohol, which is then burned off this is a less effective procedure than direct flaming but is not so detrimental to the cutting edges of instruments. 2.8 After-care of sterilized materials Equipment and chemical products that have been sterilized will, in general, only remain sterile if the access of fresh contamination is rigorously avoided. This aspect is discussed in detail under plant sterilization as it affects production equipment and the same considerations apply to raw matehals, intermediate and finished products. Even in circumstances where the aim is to achieve a low microbial count rather than absolute sterility, it is clearly desirable to restrict adventitious contamination as much as possible. Emphasis has therefore been given to matters, such as taking care to see that lids fit closely and that they are securely in place whenever possible. The fact that contamination is a dynamic process should be borne in mind. With faulty storage, product bearing a low level of contamination

794 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS may rapidly acquire a massive count without obvious sign that any change is occurring. An energetic programme of microbiological surveillance at all stages of manufacture, packaging and warehousing is the only safeguard against disastrous consequences, such as the irrecoverable spoilage of complete batches of product.