Watkins Restoration Antique
Radio Cabinet Restoration and Refinishing
including helpful tips for your radio project
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Follow this link to the page on Veneer Repair
A good place to start a discussion of the topic of radio cabinet finishing is with an excerpt from a Philco dealer service letter. This service letter went out in April 1951 explaining (bragging about) Philco's method of cabinet finishing. Here it is, brought to you by the magic of digital scanning and optical character recognition.
from April 1951 New Product News
Finishing a single Philco radio or television cabinet requires many intricate steps and delicate processes. First, staining begins only after the cabinet has been completely sanded. Stains used by Philco are made of the most unusual and expensive dyes, non-resistant, and of the type that penetrate deeply into the wood fibers so that the color remains unchanging throughout the years.
Dried over night, the stained cabinet is then sprayed with a very thin coat of crystal clear lacquer, allowed to dry and again delicately sanded, before it receives a coat of filler which makes its surface even smoother. Applied in quantity, the filler is wiped off across the grain with a special Philco material called "tow" -- a form of seaweed - until the surface is clean and dry. After drying for a minimum of 16 hours the cabinet is ready for the sealer, a specially developed lacquer, which contributes toughness and long life to the cabinet finish and prevents the finish from chipping. After the sealer has dried, the cabinet is again sanded lightly.
A coat of sealer is applied to the entire cabinet both inside and out as well. This is a great deterring factor against warpage as the wood of the cabinet is sealed against moisture both inside and out.
Now the cabinet gets its first coat of final lacquer containing a form of silica which cuts down excess gloss giving the finished cabinet a deep, luxuriant tone. Again the cabinet is allowed to dry, receives a final coat of finish lacquer, dried again, hand-rubbed, sanded, and rubbed again to remove any minute scratches and to bring up the polish. The cabinet is then ready for packing. The finishing of blonde cabinets requires even more processes and more time than ordinary mahogany. Philco's bleaching process, an alkali-peroxide solution 10 times more powerful than that in domestic use, preserves the natural beauty of the fine woods. It is applied three, four or five times, depending upon the response of the wood, each time being sponged off, dried, washed and allowed to dry again for 24 hours. It is then sanded and sprayed with a mild, clear coloring to give tone to the wood before it follows the regular mahogany cabinets through Philco's standard finishing operations.
To maintain a uniform finish during a season's production, each additional quantity of finishing material purchased is tested by the Philco Furniture Engineering Department to be sure that it meets the original specifications established as desirable for a given item. Some of the tests involve color, application, viscosity, drying time, toughness-adhesion, moisture print resistance, cold check resistance, and solvent resistance. True some of these checks are to insure a smooth flow of production. For example, an un-uniform drying time between batches could badly upset a production time table, but the net result is a benefit to the customer in being sure that whatever time in the season he may choose to buy a given model, it will have the same finish it was originally designed to have.
Sounds like lots of work, doesn't it? Reproducing this type of finish is a lot of work also. Below is an outline of the finishing process and equipment required.
Equipment used in the finishing process
Spray Application of Lacquer Finishes
- Removal of chassis, speaker, grill cloth, escutcheons.
- Assessing condition of cabinet, noting colors and patterns of original finish.
- Cleaning the cabinet
- Repairs before stripping (if necessary)
- Stripping the cabinet
- Cabinet repairs
- Initial sanding
- Application of wood filler on open grain wood.
- Application of stain (if needed)
- Lacquer sealer and sanding.
- Gloss lacquer application and rubbing
- Application of colored coats
- Satin finish coat
- Buffing the finish
Equipment and supplies used in the finishing process
Most of the equipment used in the following finishing process is readily available and inexpensive. The big exception is the spray equipment used to apply the finish. Below is a list of the equipment necessary.
- Paint brushes - 1" to 2"
- Modeler's knife - for cutting veneer patches
- Steel wool - 00 and 0000
- Sandpaper - 100 to 250 grit dry, 400 and 1500 grit wet paper
- Clamps - 5' bar clamps, various size C clamps
- Putty knives - for removing old finish
- Veneer scraps - for patching damaged veneer
- Wood scraps - for use between the cabinet and clamps
- Rottonstone or other fine polishing compound
- Spray equipment - I use an HVLP (high volume low pressure) system due to the low amounts of overspray possible with this system. The unit I have is manufactured by Fuji Industrial Spray Equipment and sold by various distributors including CMT tools. I chose this unit since it offered the best value and because Fuji has good technical support. Refillable compressed air spray can type sprayers might be a good inexpensive alternative, but I have not used them.
Spray Application of Lacquer Finishes
A short explanation of spray application of lacquer finishes is necessary to make the following how-to information understandable. Since lacquer dries quickly and temporarily softens during application of additional coats, spraying is preferred over brushing. While it may be possible to achieve good results with brushing, this is out of my area of expertise. Mixing and spraying your own lacquer has a number of advantages. When mixing lacquer, other ingredients may be added such as thinner, retarder, fish eye killer and color. Adding thinner allows you to achieve the consistency desired for a smooth finish. Retarder slows the drying time of the finish, allowing it to flow out into a smooth finish. Warm weather requires greater amounts of retarder. Fish eye killer keeps the finish from puddling up around impurities on the wood surface. Wax, silicone and other impurities can be impossible to completely remove from an old cabinet. Fish eye killer helps the finish flow over small amounts of surface impurities. Color may be adding as desired to reproduce the original finish color. Lacquer in spray cans may work well for small pieces, but it is not always a good idea on large console radios. Spray can lacquer usually does not contain adequate retarder to keep it from drying before the entire piece is coated. Lacquer in spray cans does not normally contain fish eye killer. Wet sanding between coats and extra buffing may, however, overcome some of the difficulties of using lacquer from a spray can.
Good technique is essential in producing a good sprayed finish. Each successive pass must overlap the last one by 50% for proper coverage and blending.
1. Removal of chassis, speaker, grill cloth and escutcheons:
I cover radio chassis removal under the page on chassis restoration. When you have the chassis and speaker removed, it is time to take off the escutcheon, and remove the speaker board and grill cloth. Most escutcheons fasten with several small brass screws. Remove these screws carefully, and place them in a labeled container. Be careful not to drop the escutcheon, especially if it has a glass mounted in it. Store the escutcheon in a SAFE place. One radio I restored had all the dial numbers painted on a curved glass fastened to the escutcheon. I knew that I could not replace this glass. If I broke it, all the rest of my restoration work would have been in vain. I wrapped it in bubblewrap packing and stored it in a strong box. It was not broken, and the restored radio lived happily ever after.
2. Assessing condition of cabinet, noting colors and patterns of original finish.
Once you have the chassis removed from the cabinet, look for loose parts in the cabinet. I have found knobs, screws, receipts, mouse bones, and even antique toys inside old radio cabinets. Once you have removed all loose or important items from the cabinet, vacuum the dust out. Caution! Some radios use sheets of friable asbestos under or above the chassis. See the page on Antique Radios and Asbestos.
Examine the inside of the cabinet for loose plys in the wood and for missing braces or glue blocks (those little triangular shaped pieces of wood). Inspect the outside of the cabinet for loose or damaged veneer and missing parts. If you are considering refinishing the cabinet, take pictures to document the proper color scheme. Pay careful attention to the color of the wood filler used to fill the open grain wood. You may need to take pictures after cleaning the cabinet to get the correct colors. This step is important, I often cannot remember the color scheme on a particular cabinet since restoration may take a while.
3. Cleaning the Cabinet
Clean the outside of the cabinet using #0000 steel wool and cream type hand cleaner (not the gritty type). The hand cleaner and steel wool remove all the old buildup of wax and dirt. Frequently, the cleaning will make the radio look so good, that refinishing is unnecessary. Cleaning with hand cleaner also hides scratches and imperfections. Follow these steps for successful cleaning:
Clean each side or surface separately so that the cleaner does not dry out.
Gently rub the finish with the steel wool, large amounts of pressure will remove the finish. Use more pressure as needed in small areas to remove paint or other resistant grime.
As soon as a surface is cleaned, gently rub off the dirt and cleaner with a soft absorbent cloth. Be careful not to pull up any loose veneer with the edge of the cloth.
Does the radio now look so good that refinishing is out of the question? If so, apply a coat of paste wax and you are done! You can buy paste wax at most grocery stores. Does the set look marginal? Read the page on Coming Clean or Stripping it all Off.
4. Repairs before stripping
If the finish on your radio is in really poor condition and you have decided to refinish the set, you may need to make some repairs even before you strip the set. Chemical strippers soften exposed glue. If any of the veneer is loose, the stripper may soften the glue and loosen it further. So, what needs gluing before stripping? The following list will help.
- Loose veneer that may be damaged or come loose during stripping.
- Gaps between pieces of wood that may trap stripper residue (it may be almost impossible to clean and glue later)
- Loose cabinet sides that may warp if not secured.
I recommend Elmer's woodworkers glue for almost all cabinet repairs. The glue is water soluble when wet, sets up in one half hour, and provides sturdy repairs. I use a large selection of clamps for gluing radios. C clamps from 3" to 12", extended reach C clamps, bar clamps, and strap clamps.
Use good flat pieces of scrap wood to distribute the clamping force across the repair (see picture). I use scrap wood on both sides of the clamp to avoid damage to the radio cabinet. 3/4" plywood works well for distributing the clamping force, it is hard and uniformly flat. When gluing parts under stress, I allow the repair to dry 24 hours before removing the clamps.
What about the places that cannot be clamped?
I have two tricks I use in cases where clamps will not work
- To glue loose veneer on curves and other hard to reach places, I use a clothes iron. First, I inject glue between the veneer and the substrate. I cover the part to be glued with a thin cotton cloth and iron the veneer down using a high heat. The heat and pressure cause the glue to set up quickly.
- In a few isolated cases, I cannot not use an iron since I need to draw two large pieces together (as opposed to sticking veneer down), and cannot reach the repair with clamps. In these cases, I remove a small diamond shaped piece of veneer (this shape is the most unobtrusive when replaced later) and drill a hole in the cabinet. I pass a bolt or threaded rod through the hole. Finally, I cut two pieces of scrap wood to clamp the repair, drill holes in the wood and bolt them to the area needing repairs. I thread nuts onto the threaded rod and tighten as needed to clamp the cabinet together.
To sum up, many cabinet repairs are best accomplished before stripping. I patch damaged veneer after the stripping.
5. Stripping The Cabinet
If you decide to strip the cabinet, use a good quality paste stripper. Paste stripper is available at hardware stores. Dipping the cabinet often delaminates the veneer, warps the cabinet and raises the wood grain, so I recommend radio be stripped by hand. Paint stripper is quite hazardous, so read the instructions carefully, and use the correct safety equipment (rubber gloves and safety glasses). Paint stripper will cause chemical burns on skin, especially on sensitive areas. Apply the stripper according to the instructions. Most strippers recommend brushing the stripper on with one or two brush strokes. This technique maximizes the effectiveness of the stripper. Once the finish has softened, gently scrape it off with putty knife. I use 1" and 3" putty knives on flat areas. Steel wool works well for areas with curves. Two coats of stripper usually suffices to strip the original finish. Paint or polyurethane require additional stripper. Wipe the cabinet down with a rag soaked in lacquer thinner to remove the remaining residue.
6. Cabinet Repairs
Now is the time to finish any remaining cabinet damage. First come the veneer patches. The area to be patched must be cut to a manageable shape. To make the patch less noticeable, cut in the same direction of the grain when possible. Never cut directly across the grain, cut at an angle when necessary.
When the patch area is prepared, you are ready to make the patch. The first step is to make a pattern exactly the same size as the patch area. The best way to make a pattern is to cover the patch area with a piece of paper and trace over the edges of the patch area with a pencil. It's just like the crayon rubbings you did in Kindergarten. Next, find a piece of veneer that matches the original wood (More on matching veneer later). Glue the paper with the rubbed pattern to the veneer being used for the patch. Pay careful attention to the direction of the grain when gluing the paper to the veneer. The patch will be very obvious if the direction of the grain does not match the rest of the cabinet. Using a metal straight edge and a razor knife, cut out the veneer patch. The paper will hold the patch together if it cracks along the grain (a common problem). Check the patch for proper fit. Sand the edges as needed for an exact fit. When the patch fits perfectly, glue it in place. Use the same woodworkers glue as for other repairs. Now, clamp the patch in place while it dries. Use a block of wood between the clamp and the patch for even pressure. Insert a piece of paper between the block of wood and the patch to keep from gluing the patch to the block of wood. If clamping is too difficult, fasten the patch using heat and pressure from an ordinary clothes iron (not your best iron you use for clothes). Use a medium to high heat. Apply pressure in a direction that will keep the patch from sliding out of place. A minute or two of heat should set the glue. Use steam only if needed to conform the patch to the cabinet shape (curved areas). For more detail, see the page on Veneer Repair.
7. Initial sanding
Start sanding the cabinet with 120 grit paper after stripping. If the cabinet is fairly smooth, skip the 120 grip paper and go directly to 220 grit. Always sand the wood in the same direction as the grain. Any sanding across the grain will stick out like a sore thumb. Never use an orbital sander on a wood cabinet, it will leave little circles that are extremely difficult to sand out. I always sand my cabinets by hand to make sure the sanding is not overdone. Sanding with 120 grit paper will level veneer patches, remove any left over stripper residue, and level the wood grain. Once the cabinet is smooth, use 220 grit paper to smooth the surface in preparation for the finish.
8. Application of wood filler on open grain wood
The wood filler I am writing about here is not the type used to fill nicks and gouges. Paste wood filler for filling open grain wood is made to be brushed on. You can choose from several colors. Most stores carry natural and walnut colors. Do not buy the natural color filler, it must be heavily stained for use on any radio cabinet. The walnut filler is suitable for most radio cabinets. For darker colored radios, mix in a little dark walnut stain until the wood filler is dark enough. (this is the reason I told you to note the color of the filler after cleaning the radio). Thin the filler with paint thinner according to the directions on the can. Brush the filler onto the veneered portions of the radio against the grain. This works the filler into the crevices. Apply the filler to just a portion of the radio before wiping off the excess. Do not let the filler dry before wiping the excess off (it will be very hard to remove if you do). When the filler begins to loose it's wet shine, wipe off the excess with a clean cloth using a circular motion. When most of the filler has been wiped off, use another clean cloth to remove the remainder of the residue. Once you finish applying the wood filler, use a pointed instrument to remove excess filler from corners and crevices. Allow the filler to dry for several hours. Sand the filler with 220 grit or finer sandpaper. Sand lightly in the direction of the grain. The sanding will keep the wood grain from appearing muddy after finishing.
9. Application of stain
The solid wood portions of radio cabinets usually need darkening to duplicate the original color. Oil based stains work well for achieving the proper color. I usually use Minwax brand stains since they are good stains and reasonably priced. I use the Special walnut color most frequently. I also use Dark Walnut, Mahogany, and ebony. You must brush the stain evenly to achieve good even coverage. Mix the stain thoroughly before application. Practice on a scrap piece of wood. I do not normally wipe the stain after application because the color would be too light if any stain is removed. If there are drips or uneven coverage, the stain must be wiped after application to even it out. If this happens, an additional coat of stain may be necessary (depending on the color desired).
I don't recommend oil based stains on the veneered portions of the cabinet. These stains hide the highlights in the grain and give the finish a muddy appearance. Transparent stains mixed with the lacquer work best if you need to color the veneered wood. Solar-Lux makes a variety of colors that work well with lacquer. Sometimes, the wood will not take enough stain. When this occurs, tinting of the finish is required. I will cover tinting in a later section.
10. Lacquer Sealer and Sanding
When the stain is dry, it's time to seal the cabinet. Remove any dust with a tack cloth. These sticky pieces of cheese cloth are sold just for this purpose and are available at your local paint store. Before continuing, I'll take a minute to explain why we need a sealer.
The purpose of the sealer is to seal the wood (and the wood filler) in preparation for building the lacquer finish. If we were to use the lacquer finish for the seal coat, the finish would soak into some parts of the wood more than others, producing an uneven finish. Since the sealer is thin, it soaks in and leaves little buildup of finish on the wood.
Once the cabinet is clean and dust-free, spray an even coat of sealer over the entire cabinet. Overlap the spray patterns by 50% as pictured. Since the sealer dries quickly, you can sand the cabinet within 10 or 15 minutes. The purpose of the sanding is to smooth the surface before the next coat. Sand the sealer with 250 or finer grit paper. Dry sanding works well, but make sure you change paper often. Wet sanding uses less paper, but requires more cleanup. When wet sanding cabinets, I apply water to the sandpaper, not the cabinet. Wet sanding requires paper made especially for wet use. Sand carefully or you will sand through the sealer. I use sandpaper on the flat surfaces only to keep from sanding through the finish. I use steel wool on the the remainder of the surface. If the surface is quite smooth already, you can skip the sandpaper and use 000 grade steel wool on the entire cabinet. After sanding the sealer, remove any residue with a tack cloth.
11. Gloss lacquer application and rubbing
The purpose of the gloss lacquer is to build a clear smooth protective finish over the wood. The number of coats of gloss lacquer required depends on the type of lacquer, the type of spray equipment and the desired smoothness. A high build acrylic lacquer requires less coats than a nitrocellulose lacquer. High pressure spray equipment normally requires more coats than High Volume Low Pressure (HVLP) equipment. I prefer using high build acrylic lacquer and HVLP spray equipment. This combination gives good results with only 3 coats of gloss lacquer. I mix the lacquer as follows: thinner - 10%, fish eye killer - several drops per quart, retarder - 0 to 20% depending on temperature (none for cool weather, lots for very hot weather). When the lacquer is mixed, it's time to spray!
As with the sealer, apply an even coat to the entire radio and let it dry. When the finish is dry you need to prepare for the next coat. If the finish is smooth, rub it down thoroughly with 000 grade steel wool. Rub the surface until all the gloss is gone. Do not rub hard enough to remove the finish! If the finish is textured, wet sand the flat parts with 320 grit wet paper. Make sure you use the black sandpaper made for wet sanding. Use extra elbow grease and steel wool on the parts that can't be wet sanded easily. Wet sanding will cut all the finish off the high spots if used on the areas that are not flat (routed edges, moldings, etc.) Once the finish is smooth, remove all dust with a tack cloth. You can apply another clear coat or a colored (shaded) coat.
12. Application of colored coats
Colored Lacquer darkens or tints the finish to reproduce the original cabinet color. Many radios came with colored lacquer when new. Some radio cabinets were shaded all over, others were shaded only on trim pieces or the sides. When applying a colored coat, my goal is to duplicate the original color scheme. Masking is necessary where the colored coat is in sharp contrast to other parts of the cabinet. Often, the original finish was not masked, and the colored portion has a soft edge. Duplicating the soft edge is quick, but requires skill and accuracy when spraying. Before spraying a color coat, practice on a scrap piece of wood! A cabinet may even have two different colored coats of finish, one sprayed over the entire cabinet, and another darker one just on the trim.
I use Behlen Solar-Lux stains in my lacquer. These stains dissolve easily in lacquer and produce a beautiful transparent color. Normal oil based stains tend to give a muddy look to veneers. For this reason, I use colored lacquer on the veneered portions instead of staining the wood before finishing. The colors I use are: Medium Walnut, Dark Walnut, Mahogany, and Black. I use the black to darken the walnut for very dark trim. I add 10% to 20% stain (by volume) to my mixed lacquer. I spray the color coats a bit more carefully than the gloss coats (runs are harder to fix in a colored coat). I am not as concerned that every nook and cranny get a full wet coat of finish when using a colored coat. Altering the spray pattern to cover difficult to reach areas (as done with a normal coat) increases the risk of runs. If the color coat is not quite as smooth as I want, I gently rub it with steel wool (not too much or the color goes away) and apply another coat of gloss lacquer to smooth the finish.
13. Satin Finish Coat
When the finish is smooth enough, you are ready for the final satin lacquer coat. Make sure the finish is smooth before spraying. Steel wool as needed. The final coat must be smooth, and even. I thin the lacquer just a little bit more on the final coat and add a little extra retarder, especially if the weather is warm. I spray the sides and front before the top to minimize overspray. The satin coat will look very glossy until it dries. If the finish is perfect, you are done!
14. Buffing the Finish
Sometimes, the final coat is not perfect so a little more work is needed. If the finish is rough, wet sand it with 1500 or 2000 grit wet paper. Don't sand the satin coat off, just smooth it. When the finish is smooth, you are ready to buff out the sanding marks. You can use rottonstone or some other fine buffing compound. I buff the cabinet by hand using a sponge. Electric buffers may cut through the finish. After buffing, remove the excess buffing compound and give the radio a coat of paste wax. Buff the paste wax. The cabinet now looks new!
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© 1997, 1998, 1999, 2000 Stan Watkins