Goods of the second class (6) constitute a much more important group. These fabrics are essentially of 3 kinds, viz. canvas, scrim, and paper. The former 2 of these classes possess many features in common with the round or made-up goods just described, being prepared in much the same way, saving that the fabric to be treated is usually unwound from one roller and re-wound upon another, after passing successively through the bath and a series of drying rolls somewhat analogous to those of a paper mill. Like Willesden cordage and netting, they exhibit remarkable freedom from moulding and mildewing influences.
Willesden paper manufacture may be subdivided into 2 departments, viz. (1) unwelded, (2) welded (rolled) goods, the first class being a single web or ply of paper of indefinite length passed through the bath, and rolled and dried in much the same way as canvas and scrim; the second class consisting of more than one ply or layer of primary material, incorporated into one solid insoluble sheet or homogeneous panel of indefinite continuous length.
1. Unwelded or "1-ply" paper exhibits much the same general resistance to mildewing and moulding influences as Willesden canvas and cordage. According to the nature of the paper originally treated, different kinds of 1-ply result. Certain coarse varieties furnish a waterproof material excellently adapted for lining packages and wrapping parcels liable to be exposed to damp during transit, and of special value as a first coat of paper to be applied to damp walls. Finer qualities furnish envelopes and stationery possessing the valuable property of not being affected by water. Letters written with such stationery would be as legible as ever (provided the ink were not washed away or bleached) even if the mail-bags containing them were sunk in the ocean or washed overboard, and not recovered until after long periods of immersion. In connection with this may be noticed a mode of fastening envelopes, affording security against opening and tampering with contents, impossible with ordinary gummed envelopes, or with those secured by sealing-wax, either of which, as is well known, can be readily opened by a skilled person, and re-closed without noticeable alteration (an impression of the seal being of course taken in the case of sealed letters, and subsequently used to re-seal them). This method consists in using as fastening material a concentrated cuprammonium solution; the edges of the envelope are moistened therewith, whereby the paper is gelatinised; the envelope is then closed and ironed with a warm flat-iron, when the gelatinised cellulose is converted into an insoluble cupro-cellulose, and the cover is fastened down so securely that the only possible mode of opening is to tear the paper.
No amount of steaming or treatment with water will undo the cement, as it would with a gummed envelope. Another application of this same principle consists in the use of a wafer of "Willesdenised" paper, moistened with cuprammonium solution before use. Obviously, the same principle may be applied in the direction of cementing together the edges of sheets of paper so as to form larger sheets, fixing firmly together paper, pasteboard, wood, and analogous surfaces, bookbinding, and in numerous other ways; troughs and dishes, water-tight boxes and packing-case linings are readily prepared thus.
2. Welded Willesden goods have undoubtedly the merit of being the most remarkable and interesting of all, on account of their novelty and important applications; they are all prepared in substantially the same way, viz. by simultaneously dipping more than 1 ply, and pressing into one compact homogeneous sheet the various layers, whilst still gelatinised or pectised by the action of the cuprammonium solution. According to the nature and thickness of the finished material, various subdivisions of this class may be tabulated, e. g.: - 8-ply, panel board; 4-ply, for roofing, building, panelling, decorating; 2-ply, for underlining, interior decoration, floors, damp walls, packing, leaky roofs; 1-ply, described above as un-welded Willesden goods.
Besides these, various kinds of combination fabrics may be noticed, such as those obtainable by simultaneously treating paper and calico, and welding the two together so as to form an article resembling ordinary mounted drawing paper, but differing therefrom in the important character that long-continued immersion and even long boiling in water causes not the least disintegration or separation of the 2 diverse fabrics thus combined; so that military and submarine engineers' and surveyors' plans, and the like, drawn on such paper would be uninjured by being exposed to wet and rain, if the colours or ink were of suitable kinds, so as to resist the action of the water.
Willesden 8-ply is adapted for panel work and use where great strength is required, and is valuable owing to its being made (to special order) 54 or even 60 in. wide, and in continuous lengths; from the nature of this material, there is no fear of its cracking or splitting like ordinary panel board. For boatbuilding and naval construction generally it is well adapted.
Willesden 4-ply, next to slates and tiles, stands pre-eminent as a durable roofing material, unassailable by weather of all kinds; whilst its strength, combined with lightness and flexibility, render it a most valuable and unique article for practical use and service; more especially are these advantages manifest in connection with up-country and foreign employments.
It would come far cheaper than galvanised iron, in any locality where the cost of transit is heavy, more especially in new districts where the means of communication with the seaboard are but imperfectly opened up. Again, being put up in compact rolls (ordinarily of 2 cwt. each), no space is wasted in packing. Another special advantage is, that being comparatively non-conducting, the heat of a tropical sun is less felt under a roof of this kind than under a metallic one; whilst, on the other hand, the condensation of moisture from warm air inside a hut thus roofed or walled is all but imperceptible, even on a cold night; whereas an iron building, under similar conditions, frequently gives an inconvenient drip of condensed water from the roof, and small streams running down the walls.