When the boiler has sufficiently cooled, the charge is run out by a cock in the bottom. Owing to the rotary action of the boiler the straw is in the state of fine pulp, having been almost completely disintegrated; so fine, in fact, that it flows readily through a 3-in. pipe. It is run into large tanks with perforated tile bottoms, where the excess of liquor is allowed to drain away and the pulp washed by the addition of water. It is then dug out and taken to be bleached. Before this is done, however, it may be necessary to give it a further washing. This may be done in the potcher itself. Instead of washing the straw in tanks, it may be washed in an ordinary washing engine, such as has been already described. Owing to the finely divided state of the pulp, however, this method, unless the meshes of the wire-cloth covering the drum washer are very fine, entails {101} a considerable loss of fibre. It is more suitable in cases in which the straw has been boiled in stationary boilers, and in which therefore it is less disintegrated. When stationary boilers are employed, it is not necessary to cut the straw very fine; in fact, it is sometimes put into the boiler whole. The cutting has this advantage, that it loosens the adhering dirt. In cases where the action of the soda has not been carried far, or when the straw has been put into the boiler whole, the pulp will not be disintegrated to the same extent, and it would not flow through a narrow pipe. It is necessary therefore to discharge the boiler through the doors used for filling. A novel form of washer especially adapted for straw, whereby the washing is effected with the minimum quantity of water, has been used on the Continent to a considerable extent, and to some extent in this country. The pulp is caused to pass along a series of revolving cones covered with wire-cloth, through which the liquor escapes. As it reaches the end of each cone, the pulp is emptied into a small tank containing water from the cones further on in the series. It is carried forward by means of hollow bent arms connected with the inside of the next cone, which then discharges it at the other end, to be again carried forward. As already stated, the presse-pâte system is largely adopted for straw pulp; it has been described under Esparto. It may sometimes be employed with advantage before bleaching, though it is generally used after.