Finishing And Polishing
To get a high and lasting polish on wood, the work must be first sanded so as to be perfectly smooth. In addition to this, open grained wood, such as oak, must be properly filled with a wood filler. If properly sharpened tools have been used very little sanding is required, and then worn sandpaper should be used as it does not cut into the work as new paper cuts. Remember sandpaper is not to be used as a tool in cutting down stock when working to dimensions. In using old sandpaper run the lathe at a moderate speed to avoid burning the wood, especially on square or round fillets. Keep the edges of the work sharp and do not wear them round. In using new sandpaper use a fine grit (00 or 0) and move the paper from one end of the work to the other slowly, so that no scratches result on the surface of the work.
The work may be finished by one of two methods. In the first method as in finishing ordinary cabinet work, the pieces should be stained and filled. In applying filler, run the lathe at the slowest speed after the material has dried sufficiently to rub into the pores of the wood. If the highlights are to be brought out, as in the case of oak, stain and then give a light coat of shellac, and apply the filler after the shellac is dry. The shellac keeps the dark filler from staining the flakes of the oak darker, and the pores of the wood fill in as before. The pores become darker than the flakes, and at the same time a smooth surface is produced. After the filler has hardened the wood may be waxed or varnished.
The second method, or French polishing, is rather difficult to apply and requires a little skill. A close grained wood, like maple, will be found more satisfactory for the beginner. An open grained wood may be filled in the ordinary way, or the grain may be filled by rubbing into the pores of the wood a combination of shellac, rotten stone or pumice, oil and alcohol. Rotten stone is used for dark wood and pumice is used for light wood. The wood may be left in the natural or stained as in the first method. The mixture of shellac, rotten stone, oil and alcohol, is applied to the work with a pad made of cotton waste, wrapped in cheese cloth to keep it from sticking to the work. It should be about 1½" in diameter and ½" thick. Hold the pad over the mouth of a bottle of shellac and tip the bottle so that the shellac comes in contact with the pad. The shellac will remain clean in a bottle and will be handy. The mouth of the shellac bottle should be about 1" in diameter and should be dipped once. Do likewise with a bottle, having a mouth ½" in diameter, containing alcohol. This should be dipped twice allowing the alcohol to dilute the shellac. Then drop on a couple of drops of oil and rub over the pad evenly; this aids in distributing the shellac properly and keeps the pad from sticking to the work. A bottle may also be used for this. For the rotten stone use a pepper shaker so that it may be sifted on the work as needed.
When the mixture has been applied to the pad, hold the pad against the work lightly at first, until most of the moisture has been worked out of it, and then gradually increase the pressure until the pad is almost dry. In putting on the first coat, use more shellac and alcohol and just enough oil at all times to prevent the pad from sticking to the work. However, the pad should not contain as much shellac that it can be squeezed out with the fingers. When the pad is dry, another mixture is applied, and where open grained wood is used, rotten stone, or pumice stone, is sprinkled on the work to gradually fill up the pores and to build up a smooth surface. Run the lathe at a low speed, depending on the size of the piece that is being polished. Allow the first coat to dry before applying a second coat for, if too much is put on at any one time, the heat generated in the rubbing will cause the shellac to pull, and it will form rings by piling up. These rings may be worked out in two ways, either by a slight pressure of the pad on the rings or by cutting them with alcohol applied to the pad. If too much alcohol is used it will cut through the shellac and remove what has already been rubbed on. If at any time too much shellac is used it will pile up and form rings. Too much rotten stone will cut down the polish and by absorbing the mixture will leave the pad dry. If too much oil is used the polish will become dull after a day or two.
After the first coat has hardened apply the second, but use less shellac and more alcohol and just enough oil to prevent the pad from sticking. This may be done by dipping the tip of a finger in the oil and spreading it over the pad. The entire mixture should be so that only a dampness can be felt on the pad. As the process goes on less oil and shellac are used. All oil must be removed when applying the last coat, or the piece will lose its polish. All the pores should be filled, and no rings should be on the finished work. Where a natural finish is desired, apply a coat of boiled linseed oil twelve hours before the work is to be polished. This will bring out the grain and will also aid in applying the first coat; no oil need then be used in the first coat.
A great amount of practice and patience is required to get a first class polish. Polishing can only be learned by experience. Correct your troubles in properly proportioning the mixture. Never use too much shellac as it will build up too fast and will not harden, thus causing rings; or it will pull and catch to the pad, thus forming bunches. The purpose of alcohol is mainly to dilute the shellac and to prevent against putting it on the work too fast, but care must be taken not to use too much alcohol to cut the shellac entirely. The oil helps to distribute the shellac evenly, but it must be removed when finishing the last coat, or the polish will not remain. It also helps to keep the pad from sticking to the work.
It is impossible to obtain a polish that will be as lasting and rich by any method other than the one described. For success it is essential to learn the proportions of the mixture and to acquire skill in applying the materials by using exactly the right pressure and the right movement of the pad.
Next: Face-plate And Chuck Turning
Previous: Duplicate Turning