Wallpapers are broadly divisible into two great classes, hand and machine-printed.
A few are hand-painted, principally marbles, high-class friezes, French scenic and landscape goods. Others are stencilled, or partially stencilled, and partially printed and hand-coloured a rapidly improving and increasing class. The difference between machine – printed and hand-printed goods is seen by a careful examination of the margin, which in hand- or block-printed goods shows the register of the repeat of each block.
The finish of the pattern may also be observed at the ends of the piece, a portion of plain ground being left clear of pattern at either end ; whereas in a machine-printed pattern there is an unbroken continuity. An expert will also detect the difference in colour surface left by the block and the roller.
The practical advantage gained by the hand printing is mainly that the matching of the paper is truer, and the colouring more even, an inseparable drawback to machine printing being the slight unevenness of tension which occurs as the roll of the paper passes round the printing machine rollers, and the tendency to slight oscillation of the paper from side to side. In block printing each colour or tint is printed separately.
In machine printing any number of colours can be printed at one operation, the paper coming under the whole of the variously tinted rollers one after the other before leaving the machine. Qualities. The different qualities of wall papers are many, and are mostly distinguished in the trade by the class of grounds on which they are printed.
The number of printings, except in hand-printed goods, has less influence in the assessment of cost than would be supposed. Varieties. The cheapest class of wall papers are pulps, in which the natural colour of the paper itself, either as ground or ornament, forms part of the finished surface. Then we come to grounds, in which the whole paper is coloured with a ground preparatory to printing the design upon it.
The operation of grounding the paper is done by machinery. Satins are papers in which the grounds are polished or glazed before printing, by rotary brushes actuated by machinery and the use of French chalk. Micas, golden frosted, and crystal damask are papers in which, while yet wet, the grounds are powdered with talc or mica to produce a satiny sheen. The papers are rich and effective. Embossed or stamped papers are those in which the ground or pattern, or both, are stamped in relief.
Papers which are merely given an all over texture in stamping are termed grained papers. Ingrain papers are pulps of a stout high quality, in which additional colour and apparent texture are introduced by the use of coloured fit are added to the pulp during the paper- making process. Sanitaries are papers in which the printing is done in oil colours upon a heavily sized or otherwise prepared ground.
These papers, owing to the oxidisation of the oil, become brittle and carbonised if kept in stock long, and have an objectionable gloss. Sanitums and washables, either the ground or pattern, or both, are printed in a washable distemper and spirit colour insoluble in water. They are an improvement on Sanitaries as they do not have the glossy surface. Pegamoid papers are a recent introduction, in which, after printing in ordinary colours, the paper is treated with an elastic water varnish prepared from “pegamoid.”
Metal papers, as their name implies, are papers in which pattern or ground is printed in an imitation gold, metal, or in bronze powder, and are not to be confounded with papers in which the metal is lacquered and varnished. Golds; in these the real article, gold-leaf, is substituted for the imitation.