In its unsized state the paper is too absorbent for use, and it should be sized freshly as needed for work. This is done by brushing a thin solution of gelatine over the smooth surface of the sheets of paper.
A drawing-board rather larger than the sheets of paper, placed as shown in fig. 17, with its lower edge resting on a basin of warm size, will be found a convenient arrangement.
[Illustration: Plate VII. Impression of a portion of detail from a Japanese woodblock (very nearly actual size).
The sheet gelatine sold by grocers for cooking makes an excellent size. Six of the thin sheets to a pint of water is a good strength.[3] The gelatine is dissolved in hot water, but should not be boiled, as that partially destroys the size. When dissolved, a little powdered alum is also stirred in, about as much as will lie on a shilling to a pint of water. The addition of the alum is important, as it acts as a mordant and helps to make a better colour impression.
[Illustration: FIG. 17.--Drawing of sizing of paper.]
In applying the size to the paper a four-inch broad flat paste brush is used. The paper is laid on the slanting board and the size brushed backward and forward across the paper from the upper end downward. Care must be taken not to make creases in the paper, as these become permanent. To avoid this the lower end of the sheet may be held with the left hand and raised when necessary as the brush passes downwards. The waste size will run down to the basin, but the paper need not be flooded, nor should its surface be brushed unnecessarily, but it must be fully and evenly charged with size. The sheet is then picked up by the two upper corners (which may conveniently be kept unsized) and pinned at each corner over a cord stretched across the workroom. The sheets are left hanging until they are dry. The Japanese lay the paper on the cord, letting the two halves of the sheet hang down equally on either side.
The process of sizing and drying the sheets of paper is illustrated in a print shown in the collection at the South Kensington Museum.
When the paper is quite dry it is taken down, and if required at once for printing should be cut up into sheets of the size required, with sufficient margin allowed to reach the register marks. It is best to cut a gauge or pattern in cardboard for use in cutting the sheets to a uniform size.