Radio age (Jan-Dec 1926)

RADIO AGE for January, 1926 The Magazine of the Hour 13 Finishing Your Radio Cabinet Method of Working the Wood, Applying Filler and Staining Detailed for Benefit of the Fan By H. P. STRAND IN THIS era of radio, where the fan likes to build his own, he usually selects some particular circuit or hookup, buys the parts, assembles them, makes some suitable box or cabinet, but what is it that gives his set that homemade look? It is the finish, or surface. It lacks that smooth satin appearance that usually distinguishes a factory made job from the homemade one. Now the purpose of this article is to help you get a better finish on that set you are building by going at the treatment of the wood in the proper way. The cabinet is often given the least thought in the building of a radio, and that is usually because the builder is in ignorance of the methods used to properly finish woodwork. Look at Surface Let us first look carefully at the surface of the wood. How particular have you been to eliminate all dents and imperfections? Every one will show up later, unless we get rid of them at the start. We will talk of mahogany in this article as that is the stock usually used in radio cabinets. Clear mahogany is quite easy to work, but stock with pronounced grain effects, the wide dark bands so characteristic of this popular cabinet wood is a difficult thing to handle unless great care is taken. If a hand plane is used it will be found the plane will smooth one band but will tear up its neighbor, due to the direction of the grain reversing. The best plan is to have the stock run through a small thickness planer at the mill directing the operator to have the cutting blades sharp and to take very light cuts at a time. This can be followed up with No. 0 sandpaper on a block, being sure to use a back and forth motion with the grain only. If a circular or across the grain motion is attempted it will leave scratches that can never be removed. A scraper can now be used to put the finishing touches on the stock. A good scraper to use for this work is an old safety razor blade of the variety with the stiff back edge. This will take out the tiny sandpaper marks. Apply a pressure to the blade on the forward motion only, throwing one away when it gets dull and using another one. In this way we are going to get a good surface to start with and that is half the battle in wood finishing Make sure no planer marks remain. Now For Filler T^HERE is a filler on the market that -* comes in the form of a powder that when mixed with water makes an excellent paste to fill up any little places that can not be removed by the foregoing methods. This is allowed to dry and cleaned down with fine sandpaper. If you remember that mahogany is soft when you handle it around the bench, and take care to lay some papers down and keep bits of wood and the like, from getting under your work, you won't have much filling of this nature to do. We next come to the question of staining, as the darker than natural effect is usually wanted. There are many varieties of stain on the market, so one should experience no difficulty in selecting one that will answer the purpose. A good stain will penetrate deeply into the wood, not raise the grain, or cover the grain, and its color will not fade. These stains come put up in liquid form and in both red and brown shades. It is a good plan to get some of each and mix them until the desired color is obtained. This is applied with a brush or a cloth and allowed to stand a few minutes and then the surplus is removed. A second application will produce a darker effect. It is a good idea to try some on a small piece of the same wood first to make sure of the shade. The surface must next be filled with a suitable filler. This is purchased in paste form, and thinned out with turpentine, until it is about like molasses. Apply with a stiff brush and work well into the pores of the wood, brushing with the grain and across the grain. This will fill up all the little grain marks. Allow this filler to stand about ten minutes and then remove all the surplus with a rag. Make sure that you get it all off as any remaining will affect the drying of the varnish. We next need a thin even coat of shellac. This also helps to fill the surface, as well as to make a binder for the varnish. Use orange shellac well thinned with alcohol. Apply with a brush, making quick even strokes. Applying Varnish THE first coat of varnish may now be applied. This should not be used as it comes in the can, as it is much too thick for the first coat. Dilute it with about 20% turpentine, that is, pour out in a small can enough for about the first two coats, and add about a fifth of that Tell them you read it in Radio Age quantity of turpentine. Allow this to dry over night and then sand it lightly with No. 00 sandpaper. The surface should now appear with but a slight gloss and free from lumps. Apply another coat the same as the first, and after it is dry, sand as before. Be sure to dust off well with a clean piece of cloth before attempting to put on the varnish. We can now use the varnish as it came in the can. This next coat should be applied in a room where the temperature is not less than 70°. as the varnish will not flow properly and an uneven surface will result. Make sure that no dust is in the air, and none settled around on surrounding objects or the floor, that will be stirred up and settle on the work being done. You can not be too particular on this point as the job can not come out well if the room is not clean of dust and dirt. Stir the varnish well with a clean piece of wood and make sure that it is not chilled by being left in a cold place. If it does appear thick and cold, do not use it until after it has been placed in a warm room or near the stove or heater, and had a chance to warm up. Of course, the can should be well covered during the above warming up process to eliminate the chance of dust getting into the can A good grade of bristle brush should be selected, preferably one that has been used before, as a new brush will loose its hairs until it has been broken in. Do not use a small narrow brush on a surface that is quite wide, as too many strokes will be necessary to cover the work, and the varnish can not be applied smooth and even. A one and a half inch brush on small cabinets and a two inch on large ones will be found about right. Apply this coat with long steady strokes, being sure to brush the varnish out well. Do not put it on too heavy, as several moderately thin coats are far better than one or two thick ones. Look out for "runs" and "sags," both results from thick applications of varnish and not being properly brushed out. Ready to Rub \ LLOW work to dry at least 24 hours -^* and then the first real rubbing job is ready. Procure from a piano supply house, a piece of felt, of the variety known as hammer felt, about 3x3 inches and an inch thick. This makes an excellent rubber. Thoroughly wet same in water and with a light sprinkling of powdered (Turn to page 67)