The “Willesden” goods may be divided into two classes. Goods of the first class, such as rope, cordage, netting, &c., are prepared by simply dipping the made-up materials in a bath of cuprammonium solution, using certain precautions as to the mode of immersion and its duration, and the strength of the solution. On subsequently drying the dipped fabrics, they are obtained coated and impregnated with cupro-cellulose, which thus not only forms a kind of varnish-like surface dressing, but further adds strength to the fibres by more or less intimately cementing them together.
Goods of the second class constitute a much more important group to which at present the Willesden Company more especially devotes its attention. These fabrics are essentially of three kinds, viz. Willesden Canvas, Willesden Scrim, and Willesden Paper. The two former of these classes are prepared in much the same way as the goods just described, saving that the fabric to be treated is usually unwound from one roller and rewound upon another, after passing through the bath and over a succession of drying cylinders.
Willesden Paper.—This may be divided into two departments, viz. (1) Willesden unwelded; (2) Willesden welded, the first class being prepared from a single web of paper by passing it through the bath, rolling and drying. Certain coarse varieties furnish a waterproof material excellently adapted for lining packages, &c. Finer qualities furnish envelopes and stationery, possessing the valuable property of not being affected by water. Letters written on such paper would remain perfectly legible, even after prolonged immersion. It may be interesting to point out here that the cuprammonium solution offers a very simple means of fastening envelopes in such a way as to be proof against any attempts at tampering. The method consists in using a concentrated solution as the fastening material; the envelope {220} is then closed and ironed with a warm flat-iron, whereby the gelatinised cellulose is converted into an insoluble cupro-cellulose, and the cover is fastened so securely that the only possible mode of opening is by tearing the paper.
Willesden Welded Goods are prepared by simultaneously dipping two or more sheets of paper and pressing them into one compact homogeneous sheet whilst the surfaces are still in a gelatinous state. In this way a continuous length of fabric of extraordinary durability is produced that is scarcely affected by water, even when heated in it for some weeks at a pressure of 60 lbs. per square inch.
As, on drying fabrics treated with cuprammonium solution, the whole of the ammonia in the solution absorbed by them is volatilised, it is necessary, in order to make the process economical, to collect and re-use this ammonia. This is effected by conducting the drying process in closed chambers, from which the ammonia gas is conducted by suitable appliances and recovered.
In addition to the advantages already mentioned, it may be stated that Willesden paper is much less inflammable than ordinary paper.
Among the many uses to which Willesden goods can be applied, the following may be cited:—Roofs and sheds; huts and tents; partitions; tanks and pipes; damp-proof foundations; underlining slates; sails, awnings, &c. &c.
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