SIZING.--The everyday tests as to hardness of sizing answer every ordinary purpose: Moisten with the tongue, and if the paper is slack-sized you can detect it often by the instant drawing or absorption of the moisture. Watch the spot moistened, and the longer it remains wet the better the paper is sized.

Look through the spot dampened--the poorer the sizing the more transparent is the paper where it is wet. If thoroughly sized no difference will be apparent between the spot dampened and the balance of the sheet. When there is a question as to whether a paper is tub or engine sized, it can be usually decided by wetting the forefinger and thumb and pressing the sheet between them. If tub-sized, the glue which is applied to the surface will perceptibly cling to the fingers.

TO TEST THE INK RESISTING QUALITY OF PAPER.-- Draw a heavy ink line across the sheet. If the paper is poorly sized, a feathery edge will appear, caused by spreading of the ink. Slack-sized paper will be penetrated by the ink, which will plainly appear on the reverse side of the sheet.

TO DETERMINE THE DIRECTION OF THE GRAIN.-- An easy but sure test to determine the direction of the grain in a sheet of paper, which will be found useful and worth remembering, is as follows:

For instance, the size of sheet is 17x22 inches.

Cut out a circular piece as nearly round as the eye can judge; before entirely detaching from the sheet, mark on the circle the 17-inch way and the 22-inch way; then float the cut out piece on water for a few seconds; then place on the palm of the hand, taking care not to let the edges stick to the hand, and the paper will curl until it forms a cone; the grain of the paper runs the opposite way from which the paper curls.

ABSORBING POWERS OF BLOTTING PAPER.--Comparative tests as to absorbing powers of blotting can be made between sheets of same weight per ream by allowing the pointed corner of a sheet to touch the surface of a drop of ink. Repeat with each sheet to be tested, and compare the height in each to which the ink has been absorbed. A well-made blotting paper should have little or no free fibre dust to fill with ink and smear the paper.

TEST FOR GROUND WOOD.--Make a streak across the paper with a solution of aniline sulphate or with concentrated nitric acid; the first will turn ground wood yellow, the second will turn it brown. I give aniline sulphate the preference, as nitric acid acts upon unbleached sulphite, if present in the paper, the same as it acts upon ground wood, viz., turning it brown.

Phloroglucin gives a rose-red stain on paper containing (sulphite) wood pulp, after the specimen has been previously treated with a weak solution of hydrochloric acid.

About the end of the eighteenth century it became necessary to make special papers denominated "safety paper." Their manufacture has continued until the present day although much limited, largely because of the employment of mechanical devices which seek to safety monetary instruments. Such safety papers are of several kinds.

1. Paper made with distinguishing marks to indicate proprietorship, as with the Bank of England water mark, to imitate which is a felony. Or the paper of the United States currency, which has silk fibers united with the pulp, the imitation of which is a felony.

2. Paper made with layers or materials which are disturbed by erasure or chemical discharge of written or printed contents, so as to prevent fraudulent tampering.

3. Paper made of peculiar materials or color, to prevent copying by photographic means.

A number of processes may be cited:

One kind is made of a pulp tinged with a stain easily affected by chlorine, acids, or alkalis, and is made into sheets as usual.

Water marks made by wires twined among the meshes of the wire cloth on which the paper is made.

Threads embodied in the web of the paper.

Colored threads systematically arranged were formerly used in England for post-office envelopes and exchequer bills.

Silken fibers mixed with the pulp or dusted upon it in process of formation, as used in the United States currency.

Tigere, 1817, treated the pulp of the paper, previous to sizing, with a solution of prussiate of potash.

Sir Win. Congreve, 1819, prepared a colored layer of pulp in combination with white layers, also by printing upon one sheet and covering it with an outer layer, either plain or water-marked.

Glynn and Appel, 1821, mixed a copper salt in the pulp and afterward added an alkali or alkaline salt to produce a copious precipitate. The pulp was then washed and made into paper and thereafter dipped in a saponaceous compound.

Stevenson, 1837, incorporated into paper a metallic base such as manganese, and a neutral compound like prussiate of potash, to protect writing from being tampered with.

Varnham, 1845, invented a paper consisting of a white sheet or surface on one or both sides of a colored sheet.

Stones, 1851. An iodide or bromide in connection with ferrocyanide of pota.s.sium and starch combined with the pulp.

Johnson, 1853, employed the rough and irregular surface produced by the fracture of cast iron or other brittle metal to form a water mark for paper by taking an impression therefrom on soft metal, gutta- percha, etc., and afterward transferring it to the wire cloth on which the paper is made.

Scoutteten, 1853, treated paper with caoutchoue dissolved in bisulphide of carbon, in order to render it impermeable and to prevent erasures or chemical action.

Ross, 1854, invented water-lining or printing the denomination of the note in colors while the pulp was yet soft.

Evans, 1854, commingled a lace or open-work fabric in the pulp.

Courboulay, 1856, mixed the pulp and applied to the paper salts of iodine or bromine.

Loubatieres, 1857, manufactured paper in layers, any or all of which might be colored, or have impressions or conspicuous marks for preventing forgery.

Herapath, 1858, saturated paper during or after its manufacture with a solution of a ferrocyanide, a ferriccyanide, or sulphocyanide of pota.s.sium, sodium, or ammonium.

Seys and Brewer, 1858, applied aqueous solutions of ferrocyanide of pota.s.sium or other salts, which formed an indelible compound with the ferruginous base of writing ink.

Sparre, 1859, utilized opaque matter, such as prussian blue, white or red lead, insoluble in water and stenciled on one layer of the paper web, forming a regular pattern; this was then covered by a second layer of paper.

Moss, 1859, invented a coloring matter prepared from burned china or other clay, oxide of chromium or sulphur, and combined it with the pulp.

Barclay, 1859, incorporated with the paper:

1. Soluble ferrocyanides, ferricyanides, and sulphocyanides of various metals, by forming dibasic salts with pota.s.sium, sodium, or ammonium, in conjunction with vegetable, animal, or metallic coloring matters.

2. Salts of manganese, lead, or nickel not containing ferrocyanogen.

3. Ferrocyanides, etc., of pota.s.sium, sodium, and ammonium, in conjunction with insoluble salts of manganese, lead, or nickel.

Hooper, 1860. Employed oxides of iron, either alone or dissolved in an acid, and mixed with the pulp.

Nissen, 1860. Treated paper with a preparation of iron, together with ammonia, prussiate of potash and chlorine, while in the pulp or being sized.

Middleton, 1860. Joined together one portion of a bank note printed upon one sheet of thin paper and the other part on another; the two were then cemented together by india-rubber, gutta-percha, or other compound.

The interior printing could be seen through its covering sheet, so that the whole device on the note appeared on its face.

Olier, 1861. Employed several layers of paper of various materials and colors; the middle one was colored with a deleble dye, whose color was changed by the application of chemicals to the outer layer.

Olier, 1863. Prepared a paper of three layers of different thicknesses, the central one having an easily removable color, and the external layers were charged with silicate of magnesia or other salt.

Forster and Draper, 1864. Treating paper during or after manufacture with artificial ultramarine and Prussian blue or other metallic compound.

Hayward, 1864. Incorporated threads of fibrous materials of different colors or characters into and among the pulp.

Loewenberg, 1866. Introduced prussiate of potash and oxalic acid or such other alkaline salts or acids into the pulp, in order to indicate fraud in the removal of cancellation stamps or written marks.

Casilear, 1868. Printed numbers on a fugitive ground, tint or color in order to prevent alteration of figures or numbers.

Jameson, 1870. Printed on paper, designs with ferrocyanide of pota.s.sium and then soaked the paper when dry in a solution of oxalic acid in alcohol.

Duthie, 1872. Made a ground work of writing ink of different colors by any known means of pen ruling.

Syms, 1876. Produced graduated colored stains, which were made to partially penetrate and spread in the pulp web.