The so-called toned paper is produced by adding to the pulp a solution of pernitrate of iron, from which a fine precipitate of oxide of iron is deposited on the fibres; thus the slightly brown shade characteristic of this kind of paper is produced. The same effect may be produced by the addition of yellow ochre or some similar pigment. The following are a few of the materials which are used for producing coloured papers:—Methyl violet, eosine, chrome yellow, venetian red, catechu. Useful receipts for the preparation of coloured papers will be found in Dunbar’s ‘Practical Paper-Maker.’ {143} During the time that the loading, sizing and colouring processes have been going on, the pulp has been continually acted upon by the roll, and if these operations have extended over a considerable time, it is probably in a proper condition for making into paper. The amount of “beating” depends, as has been stated before, upon the nature of the fibre, and also to some extent on the nature of the paper for which it is intended. The “beaterman” examines the pulp from time to time by taking a portion from the engine and placing it in a hand-bowl containing water: from its appearance when so diluted he is able to judge of the time during which it may be necessary to continue the disintegration. As soon as this is completed, the pulp is ready to be let down to the stuff-chests, usually placed at a lower level than the beaters, so that the pulp can flow into them by gravity. For this purpose the valve at the bottom of the engine is opened: to remove the last portion of pulp it is necessary to rinse out the engine with water. TABLE.—STRENGTH OF ALUM SOLUTIONS (17·5° C., 63·5° F.). +------------------------+-------------------+------------------+ |Percentage of | Specific Gravity. | Degrees Twaddle. | |K_{2}Al_{2}(SO_{4})_{4} | | | |+ 24 H_{2}O. | | | +------------------------+-------------------+------------------+ | 1·0 | 1·0065 | 1·30 | | 2·0 | 1·0110 | 2·20 | | 3·0 | 1·0166 | 3·32 | | 4·0 | 1·0218 | 4·36 | | 5·0 | 1·0269 | 5·38 | | 6·0 | 1·0320 | 6·40 | +------------------------+-------------------+------------------+ {144} CHAPTER X. PAPER MACHINES; HAND-MADE PAPER. The pulp as it comes from the beaters is now ready to be made into paper. We will first consider briefly the manufacture of hand-made paper. It is made on a mould of wire-cloth, with a movable frame of wood, called the “deckle,” fitting on to the outside of the mould and extending slightly above its surface.