Part 2 (1/2)

The following may be subst.i.tuted for the above:--

Plaster of paris 2 lb.

Flour 2 lb.

Gelatine 4 oz.

A transfer paper with its surface granulated to represent a mechanical stipple, or the texture of a grained stone, may be prepared in the following manner. Take of:--

Starch 9 oz.

Parchment chippings 12 oz.

Flake white 14 oz.

Prepare the starch as previously described, and dissolve the isingla.s.s by boiling. Mix the flake white into a thin paste by the addition of water. Warm the three ingredients, and mix the whole thoroughly. Coat a fairly heavy printing paper twice with this composition, and when it is thoroughly dry give it the required granulation by means of grained stones or engraved plates. The grain thus imparted breaks up the drawing into a series of minute dots. Paper of this description is most suitable for pencil or crayon work. Its usefulness is obvious. It enables the artist to use his chalks in the usual manner, without the inconvenience of handling large stones. No graining of the stone is necessary, and the grained effect can be confined to any portion of the design.

Photo-litho transfer paper is in every respect a specific article, the coating of which consists of a gelatinous emulsion, which can be readily sensitised, and upon which a photographic image can be developed.

Special preparation and manipulation are therefore necessary in connection with its production, and these points will be fully dealt with in a subsequent chapter.

One more variety of transfer paper should be mentioned, namely, the diaphanic, which possesses excellent qualities for certain cla.s.ses of work. It is very transparent, and extremely useful in the tracing of key formes, or for making facsimile drawings for immediate transference to stone.

CHAPTER IV

COPPERPLATE TRANSFER PRINTING

The Copperplate Press--The Operation--Charging the Engraved Plate--Cleaning-off and Polis.h.i.+ng--Making the Impression-- Useful Notions.

Although copperplate printing may not now be so extensively practised as in years gone by, it is not, so far as we can judge, very likely to be superseded in the near future. It is still regarded as a necessary adjunct to lithography, especially where the amount of commercial work produced is of any moment.

From a purely mechanical point of view the construction of the copperplate press (Fig. 3) is of an exceedingly simple character. Its primary purpose is to produce a heavy and uniform pressure on the plate during operation.

[Ill.u.s.tration: FIG. 3.]

After being charged with a special pigment and cleaned as hereafter described, the plate is laid, face upwards, on the iron bed or table of the press and in contact with the paper, and pa.s.sed through between two iron cylinders. These cylinders are so adjusted as to produce an exceptionally heavy pressure. Such are the simple elements of a process which, however, requires much closer investigation.

In its application to lithography the following are the only requisites for copperplate transfer printing.

A stick of prepared transfer ink--whiting, free from grit--transfer paper, and a plentiful supply of soft rags. Likewise, an iron plate with a gas jet underneath (Fig. 4), a square of printer's blanket, and a damp book consisting of twenty or thirty sheets of blotting or other absorbent paper slightly and uniformly damped.

[Ill.u.s.tration: FIG. 4.]

A good copperplate transfer paper can be made according to the recipe given in Chap. III., but unless a fairly large quant.i.ty is used the commercial qualities will be found most economical.

Copperplate printing, in its application to lithography, is a simple operation, but it requires extraordinary care for its successful execution. The conditions under which lithographic transfers are made from a copperplate engraving are vastly different from those which control copperplate printing for ordinary purposes of reproduction.

The engraved plate is first well heated by means of the hot plate already mentioned. The transfer ink is then _forced_ into the engraved parts until every line is fully charged, the ink having been previously enclosed in a double fold of soft rag.