BOTTLE CLOSURES 365 BOTTLE CLOSURES A Lecture delivered to the Society on Thursday, January 5th, 1956 S. F. TOWNSEND.* The author gives details of the make-up of the many varieties of bottle closure. He discusses their advantages and disadvantages for the different purposes for which each is customarily used. FUNDAMENTALLY, closures, as the term is commonly interpreted, can be divided into two types, these being plugs and screw or snap-on caps. To deal with the first, closures of the plug type in common use are corks, glass stoppers, rigid compound screw stoppers with rubber rings, rubber plugs, polythene stoppers and porcelain swing stoppers with rubber rings. A feature of all plug type closures that should be recognised is that all types occupy internal space in containers, and to a varying degree compress the air space or vacuity in containers. For some bottling purposes this is of little consequence, but with the bottling of volatile liquids or where there is little air space in containers this feature must be considered. In regard to this, a general principle that is practised in the wine and spirit bottling trade is to allow 3• to 4 per cent of closure volume as air space so far as the bottle manufacturers are concerned it is recognised practice to do this. CORKS As we know them these are by far the most commonly used of plug-type closures. The manufacture of these is a specialised craft which is largely centralised in Portugal and Spain. The cork wood from which they are made originates from the cork oak (Quercus suber), which is tound in various Mediterranean countries, the largest concentrations being in Portugal, South Spain, and the coastal belt of North Africa. Cork wood is oi microcellular structure, the air space being about 50 per cent of total volume. The solids in the main are composed of ligneous tissue, organic acids such as tannic acid, and resins. The moisture content is normally between 2 and 6 per cent. It is affected by strong acids and alkalis, also it is, in effect, slightly porous to volatile solvents. However, it withstands ageing very well and has been found satisfactory for a multitude of closure purposes. Normal corks are punched so that pores run across and not from tip to top. In use this prevents seepage of bottled liquids through pores. The only exception to this are large corks or bungs that are used on carboys and jars these are cut with the outside of cork bark on top. * Armstrong Cork Co., Ltd., London, N.W. 9.

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Corks are supplied in various shapes, the most popular types being tapers and parallels. A common modification made with parallel corks is to cut or shape a bevelled or rounded point. For certain bottling purposes, such as gin, corks are supplied with clean points or tips. This is done by 100 per cent hand sorting and notching out pores on points of corks, which minimises dust effect from corks, but is expensive. It might be said that the aristocrat of corks are those used for the bottling of champagne only the finest quality selected wood is used in the manufacture of these, and most are made of three Ol four pieces. In use it is common for champagne corks to be com- pressed to one-third of original volume when in bottle necks. For certain purposes corks are treated with hot or cold paraffin wax, and, on the Continent, lacquer. Paraffin wax acts as a lubricant also these treatments minimise dust effect from corks. A particular feature of modern cork closures is the popularity of the flange top that is put on, or is shaped as an integral part of cork. This can be seen in common use on wine, spirits and fruit juice bottles. Flange tops can be made of decorated wood, decorated metal, wax compound or plastic. It helps easy removal of closure from the bottle and also serves a decorative and descriptive purpose. The composition type of cork closure is usually of conventional cork shape and is made of granulated cork, binder and possibly plasticiser. This was used to some extent before the last war as a wide mouth type of closure this use, however, has been largely superceded by the use of screw caps. Another purpose for which composition cork plugs are used at present to a limited extent is the bottling of such materials as Vin Ordinaire on the Con- tinent. In this case, the corks are presumably manufactured by a cheap moulding process which enables the product to be sold at a highly competitive price. GLASS STOPPERS The quantity of ground glass stoppers used commercially appears to have diminished if this is not precisely true, it is a fact that the percentage of glass-stoppered bottles used has diminished. Two possible reasons for this are: Expense: every stopper has to be hand fitted by carborundum grinding to each individual bottle. Misuse: there are two major ways of misusing glass stoppers the first is to allow a stopper to lose its original bottle with the probable consequence of a leaky closure. As acids are often the concerned bottled matehals, this can be dangerous. The other is to use them without lubricant this can be harmless as far as a decanter of brandy is concerned, but the instances of jammed stoppers in bottles of