The papers are put back into the press without felts between the sheets and left for some time. In most cases the sheets are turned round or mixed in with the sheets of another pile, before pressing. In this way any unevenness or irregularity in the sheets is counteracted and a more uniform result obtained. When these changes are repeated several times the paper acquires an even texture and becomes firm and hard. _Drying the Paper._--The sheets are hung up in the _loft_, as the drying room is called, upon poles or ropes. The moisture gradually evaporates, and the paper is thus dried by exposure to air. In winter it is necessary to warm the air in the loft, as the air is then saturated with moisture. In lofts of limited capacity the air is heated in order to hasten the process, but the best paper is allowed to dry naturally, as by this means the shrinkage is gradual and a maximum strength is attained. [Illustration: FIG. 15.--Apparatus for Sizing Paper in continuous Rolls.] _Sizing the Paper._--The dried paper as it leaves the loft is termed _Waterleaf_ because, being unsized, it readily absorbs water, and therefore before it can be used it must be sized. For this purpose it is dipped into a solution of gelatine, an operation described as _tub-sizing_ or _animal-sizing_, the former term being used on account of the tub in which the size is kept, and the latter on account of the fact that the gelatine is made from animal matter such as hides, cartilage, hoofs, and other refuse. _Animal Size._--This is prepared from hide pieces, skins, and the like by a simple process, which, however, requires a good deal of care in order to obtain the best results. The material is first thoroughly washed in plenty of clean water, and then heated with a definite quantity of water in a steam jacketed copper pan. The pieces slowly dissolve until a solution of gelatine is produced, and after the dirt and impurities have settled to the bottom of the pan the clear liquid is drawn off into store vessels. There are many details of a technical character to be attended to in the manufacture of good gelatine, and as the process is expensive, considerable attention is demanded at this stage in the completion of a sheet of paper. The dry sheets of paper are sized by the simple expedient of dipping, or by the passage of the paper through a long trough. In the first case the workman takes up a number of sheets and dips the bunch into a vat of size at the proper temperature, about 100° Fahrenheit. He then allows the surplus size to drain off, and the sheets are submitted to a slight pressure in order to remove the excess of gelatine that will not drain off.