If it is desired that the brush make thicker strokes under pressure, the ordinary condition of it, in which all the bristles come to a point, is quite sufficient. But it is very difficult to lay on strokes of uniform thickness with them. Press the brush on the table, spread the bristles fanwise with a knife and cut away from each side about a half-line deep. Turn the pencil to the other side, stroke it again to spread it, and cut the same amount as before from each side. Continue this till there remain only ten or twelve bristles of the original length in the brush. Then cut these even at the ends. These should not be altogether the middle ones if the pencil is to be first-class. Neither should they be too far apart. They should hang together well when the brush is dipped into the ink, but not so closely that they will not let the ink pass well. With a brush successfully trimmed thus, the handsomest drawings, resembling copper plate, can be done with ease.
For coarser strokes, coarser brushes are needed. More bristles are permitted to remain in them.
III
CONCERNING ENGRAVING NEEDLES
These serve for the intaglio process, to draw into the stone, and must be of the best and hardest steel. In Munich there are also used the little five-angled watchmakers' borers, which are glued between two pieces of wood planed round in form of a pencil and so cut at the end that only a bit of the tool is visible. In using very thin needles one has the advantage that they are ground and sharpened easily.
For coarser strokes, coarser needles are needed. For fine strokes, especially if they are to go in all directions, the needles are best ground perfectly round.
IV
CONCERNING THE DRAWING-MACHINE
To transfer drawings very accurately and reversed on the stone, which is necessary especially in the case of charts and plans, a pantograph is used in Munich, which is so arranged that the stone is upside down and elevated. The inscribing-needle is just opposite the one that is managed by the hand, and when one follows the lines of the original exactly, there results a perfect but reversed copy on the stone. Such drawing-machines can be obtained from Herr Liebherr and Company in Munich. This skilled mechanician also makes a sort of pantograph of his own invention, with which drawings can be transferred to stone, reversed or otherwise, and in any desired proportion. Pictures of such machines may be obtained from him.
V
CONCERNING OTHER APPLIANCES
These are: a grinding-table, an etching-trough, some rulers, a writing-table, some music-writing pens and rastrums for those who wish to print music, small brush for spatter-work, a wiping-machine for the wiping method, several rollers and balls for inking, and some presses for wetting and pressing the paper.
Any firm table may be used for grinding, but it is better to have one made heavy enough to resist the strain of the powerful friction, and so made that the stones can be fastened on it readily. If this work is done in a room, it must have a depression in the middle and a hole, that the water may run off into a receptacle. Along the sides should be a low rim, that the sand and dust may not drip all over the floor.