The next process is that of thoroughly washing the gun-cotton, for the purpose of removing the traces of the acid still adhering to it. By pulping, which operation is performed in pulping engines or beaters, the washing is expeditious and thorough.
A beater is an oblong tub in which is placed a revolving wheel carrying strips of steel on its circumference. From the bottom under the wheel project similar steel strips.
The action of this machine is as follows:—
By the rotation of the wheel, the gun-cotton which is suspended in water circulates around the tub, and is drawn between the two sets of steel projections, by which it is reduced to a state of pulp.
The bottom of the tub is movable, and thus the space through which the gun-cotton must pass may be contracted, as the operation proceeds.
The pulping being complete, the contents are run into poachers for the final washing.
A poacher is a large oblong wooden tub. On one side at the middle is placed a wooden paddle-wheel, which extends half way across the tub.
In the poacher the pulped gun-cotton is stirred for a long time with a large quantity of water. The revolution of the paddle-wheel keeps up a constant circulation, and care is taken that no deposit occurs in any part of the tub.
Having converted the cotton into gun-cotton, reduced it to a state of pulp, and thoroughly washed it, the next process is to separate the water from the pulp, and compress it into cakes or discs.