There are three distinct processes in polishing a pebble—grinding, smoothing, and facing. Let us take this pebble, a choanite, of a kind which I found at Sandown, Isle of Wight, and which I polished in the first of the only four lessons I ever had. It is a beautiful little rounded choanite, rather flattened on the upper and under surfaces. It is too small to be held comfortably between the thumb and two first fingers. We must therefore fix it upon a cement-stick. So we must manufacture some cement as follows. Here is the recipe:—
Fig. 4.
Fig. 5.
1 lb. of pitch, 1⁄2 lb. of resin, 1⁄4 lb. of shellac, 1 oz. of beeswax, must be broken up and put into a good-sized saucepan. Begin boiling the mixture upon a fire, and as it boils add gradually 11⁄2 lb. of Spanish brown, stirring all the while until all the ingredients are thoroughly mixed. Pour the contents of the saucepan upon the stone flags of the kitchen floor, or any pavement, in portions a foot in diameter. When cold remove the cement by a kitchen knife inserted underneath. Make some pieces of wood 4 in. long according to the shape in [Fig. 4], and melt on them a portion of cement as shown at B. A nail driven into the wood at A and C will strengthen the cement. Fashion the cement into shape with the fingers well wetted. Warm the stone, and again melt the cement over a candle. Apply it to the stone, and work it on with the fingers. Be sure you have the stone firmly fixed. To test it, plunge the stone and stick into water, and when it is cool see if you can pull the stone off. The diagrams in [Fig. 5] show the phases of cementing a stone. If the stone is insecure, pull it off, and warm and melt up again. Practice makes perfect.
The first stage is that of GRINDING. Set up the lead lap as shown in the drawing of the bench ([Fig. 1]). Put a heap of emery in the left corner of the right compartment (J). Put a jam-pot of water at Z. Take the old blacklead brush, dip it in water, mix up some emery with it into a paste; wet the lap; brush it well over with emery. Take your cemented stone in the right hand, between the thumb and two first fingers; turn the handle N slowly from right to left, and as the lap revolves press the stone upon it. Grind away, understanding that you want to grind down all irregularities on the surface of the pebble. Try and throw the weight of the body through the right arm and wrist into the pebble. Emery is harder than flint. The pressure forces the emery into the lead lap, and so its surface is converted into a powerful rasp. Pause at intervals to brush fresh emery over the wheel. ‘Don’t spare your emery!’ was an exhortation I often heard when receiving my lesson. Do not attempt to do the whole surface of the pebble at once. Begin at a corner and finish it fairly, and so pass on to adjacent parts. Work towards the centre of the lap when grinding round surfaces, and keep the flat margin of the lap for flat stones.
Ah, your right hand begins to ache as it never ached before! You must not mind. Rest a while, and then at it again! You are bringing muscles into play which are unaccustomed to the work, and the strain will be felt until the muscles are strengthened by the exercise. Keep washing the pebble at intervals with the nail brush in the earthen vessel to see how the work progresses.
The surface of the pebble where you have been working now looks smooth, and the feelers of the choanite are vividly shown. Finish in the same manner the whole surface. Feel that you bring the weight of the arm—and even of the body—to play through the wrist of the right hand upon your stone. Do not forget the emery and washing, and see that you keep the surface of the stone true and free from ‘ridges’ and ‘shoulders.’
When you think the surface is sufficiently ground, then continue working on the lead without putting on any more emery. Continue patiently so grinding until the lap works perfectly free from grit, and the emery on it has been reduced to soft black paste. This will make the surface of your pebble much smoother. The nearer you reach perfection in this first stage the easier will be the afterwork. If you continue long enough the stone will look half polished when dry before you have finished. Dry the stone periodically to estimate progress, remembering that a pebble always looks polished when wet.