Size

The size must be considered next. It may be applied to the pulp or to the sheet, and may consist of gelatine with a little alum, of colophony or rosin dissolved in soda-lye, followed by treatment with alum or alum-cake. Sometimes starch is used along with alum or alum-cake. From good drawing-papers, which are sized in the sheet with animal size, the greater part of the size may be extracted by means of boiling distilled water, the solution being usually neutral or faintly acid, sometimes faintly alkaline, to test-papers. Gelatine and starch, to the extent of about 5 percent of the weight of the paper, are the safest sizing materials.