WAX AND THE COSMETIC CHEMIST tan wax (being an ester wax of mineral origin) was excluded, as well as all the other waxes. One of the main requirements was a high content of unsaponi- fiable matter (see above, oils and fats), usually of the order of about 50 per cent (although not limited in either direction). The term was not related either to state of matter or to any properties. acting as carriers or vehicles for dyes, pigments or medicating additives (carbon paper, cosmetics, pharmaceuticals, etc.), and--at least in principle--suitability for use as a solid illuminant, as well as a mouldi.ng material. (Re emulsifiability, see ma•n text "Waxes v. Related Mater- ials"). All waxes must be compatible with each other and with oils and fats, as well as soluble in fat solvents at a raised tempera- ture. There are, as already stated, no limita- tions as to origin or chemical composition. Wax Substitutes .' Materials which are de facto used as waxes, but are not ful- filling the "True Wax" defini- tion were given' all sorts of names, such as "wax-like" materials, "physical waxes," "practical waxes," etc. Related Materials: There are numerous substances out- wardly exhibiting a certain similarity to waxes, which are, however, not fulfilling some or many of the essential, technologi- cal requirements for waxes. They are frequently used in conjunction with waxes and may, for certain purposes, serve as a replacement material for some of them. Chemically, they are in many instances akin to waxes, inasmuch as also the related materials are, as a rule, chain- compounds. Naming them in accordance with their chemical composition, which usually is much more simple than that of waxes. and/or with a trade description might in the end also be an advantage so far as the manufacturers are concerned. (See also main text.) Resi•s .' In the past, resins were solely defined by their chemical com- position very involved sys- tems of classification had to be used for this purpose. Synthetic resins and similar materials were frequently ex- cluded. Resins .' They are no longer defined by their chemical composition or in accordance with their origin, but by their specific physical (i.e., their technological) charac- teristics. Synthetic products--often also thermo- plastic and thermosetting materials--are included. Main differences from waxes are: transparency and brittleness in the solid state, high melt-viscosity, and a tendency to set as such--and in the form of solutions--with surface gloss usually not further enhanced by ordinary buffing. 135

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS In contrast to waxes, many resins are soluble in polar solvents. Relatively few resins are compatible with waxes. ThermopIastics .' They differ from waxes principally by their usually much greater molecular weight, higher melting-point, greater toughness, lower crystallinity, and super- ior temperature stability. Solubility in fat-solvents often is, even at a raised temperature, technologically insufficient to some extent the same is true also with regard to certain waxes. Concerning the order of the melting point, there are also high-melting waxes (chiefly •f the amide type, ignoring metal- soap-containing compositions), but they are lacking the plastics' requirements. WAXES V. RELATED MATERIALS The preceding definitions also summarise the salient differences between waxes and "related materials." So far as the cosmetic industry is concerned, representatives of both groups have to satisfy the following requirements, namely' they must be harmless, free from unpleasant or strong odour, and colourless or light-coloured ß they must not cause irritation of the skin they must have no deleterious effect on perfumes or medicating additives, and no tendency to turn rancid' they should act as stiffening agents, and/or as a basis for ointments, or serve as emulsifying agents (as such or in conjunction with mild alkalis, soap, or the like), or as modifying agents (e.g., for texture) in certain cases, such as lip-sticks, hair creams, etc., gloss-effect is required (but this is caused by the fatty materials used, rather than by the waxes) most of the materials concerned possess, at least to some extent, emollient action. The principal waxes used for the manufacture of cosmetics are :- beeswax (yellow and bleached), paraffin waxes, microcrystalline waxes, petrolatums (waxes, besides petroleum jelly) ' to a lesser extent (at least as a rule), the following waxes are used ß spermaceti, 136