For the operation of "setting" the bow is left about half as thick again as the finished stick is intended to be: this to allow for scorching or burning the outer surface. When the "setting" is satisfactorily accomplished the stick is planed up round, after which the bottom trench is cut. This is the slot in which the screw-eye of the nut travels. Then the hole for the screw itself is drilled out in a lathe fitted with a "Cushman chuck." The next thing is to put on the "black face." This is a thin slab of ebony glued on to the under surface of the head, which helps to strengthen the head and forms a solid bed for the ivory or metal plate which forms the outer facing of the head. The ivory faces are cut out of the solid tusk to the shape shown in Fig. 36. They are glued on with the very best glue procurable and tied down with strong twine. This is another matter of extreme difficulty and delicacy, as ivory is a very stubborn material to work in and it is easy to crack it in forcing it down to the curve of the face, that is if it is sufficiently thick adequately to fulfil its original purpose as a strengthener and protector of the head. One often sees in cheap bows faces of ivory so thin as to show the ebony face through in a bluish tint. Such a face is of as much value to the bow as a piece of paper, but it was easy to put on! [Illustration: FIG. 36.] Metal faces are growing more and more into favour but, personally, I prefer a substantial ivory face, for though the metal may be stronger in itself I think an ivory face well glued on is more homogeneous. The successive layers of ebony and ivory on the already hard wood forms a more equal gradation of density. After both the faces are adjusted a circular hole is drilled in the head and then chiselled out square to form the top trench or box to receive the hair. The nut is then fitted. Many people imagine that even the best makers buy the nuts wholesale and fit the sticks to them, but good makers always make the nut for each bow as it is wanted. They can by this means better regulate the balance of the bow. [Illustration: FIG. 37.] Fig. 37 shows a gauge to determine the various dimensions of the nuts of violin, viola and 'cello bows. Before the bow is finally "cleaned up" it is haired[1] and screwed to see if it is all true, for there may be something faulty in the _cambre_ which can be corrected at this stage. If all is satisfactory the bow is finished and polished, the whole process, from the rough stick in Fig. 34 to the finished bow ready for the artist to melt, delight and amuse his hearers, being one day's work. [Footnote 1: For details of bow hairing see Chapter XII.] CHAPTER XI. POSSIBLE REPAIRS--SPLICING--RENEWING CUPS--RESTORING THE NUT--RE-FACING.