View Full Version : Repairing and Restoring Varnished Hardwood
03-10-2004, 03:41 PM
Have a valuable piece of old boat bright work or furniture that is broken around the hardware? Yes…my training aid today is an old walnut gunstock from 1936, but these objects are subjects of close inspection by discriminating clients, and require a degree of precision useful for demonstration. Plus, as the techniques and materials are slightly different from other disciplines, it’s also good cross training…. the various woodworking specialties would be well served to cross-fertilize more. Want to learn to bed hardware perfectly? Learn from a stockmaker. Want to achieve perfection with card scrapers on expensive and fragile, highly figured wood? Watch a luthier. Restoring original finishes? A museum furniture conservator. Steambending? A traditional boatbuilder or chairmaker, of course.
The workpiece was severely damaged in a fall, and has other problems. Sometime in its past it acquired a sling swivel that will be removed, a missing chip that will be repaired, several dents, and was stripped and refinished separate from its matching walnut forearm…they are no longer the same color. How do I know the stock is original to the rifle? I can’t be absolutely sure, but examination of the inletting surfaces and comparing them to the forearm show the walnuts to be of the same age and probably from the same supplier, which is the single most important factor in matching color. The firearm in question is one of the first of its model manufactured; has some value, and I’ll restore it…not to new condition, but to appear like a used but well-cared-for representative of its type in excellent original condition.
West System 5:1 boatbuilder’s epoxy when thoroughly mixed has a dab of walnut epoxy dye added….
…and is applied unthickened to all the broken wood surfaces to be repaired…the main portion of the stock at the breaks is heated gently to thin the applied epoxy for the deepest possible penetration into wood and down cracks with the aid of a thin dentist’s spatula…more epoxy is applied if necessary…
…the pieces are assembled and clamped to cure using a few rubber bands thoroughly waxed first with common paste wax. Cleanup is with a vinegar-dampened rag.
While the breaks at the inletting cure, we attend to the remaining damage…a swivel screw hole and toe chip. I’ll fill these with wood of the exact species, grain and approximate age from my collection of scraps.
From a scrap of identical cut and grain I make a 3/8” plug and slice a patch…
…then drill a matching hole with a sharp Forstner bit (you don’t need a pilot for accuracy…simply tap it with a light brass hammer to set…then drill by hand slowly) …file the chip flat…
…and simply rub or drive the patches to a tight fit without clamping and let cure. The screw hole is deeper than the plug patch and was filled with epoxy. Line up the grain exactly. I quit for the day and place the leftover epoxy in the freezer to save it for use tomorrow.
03-10-2004, 03:42 PM
Next day, I reinforce the repaired inletting with epoxy for strength, bedding the receiver tang in the process. First, I rout the wood to receive epoxy with Dremel ball and point cutters to expose fresh wood and to provide enough epoxy thickness to prevent chipping from recoil forces. Fortunately, this inletting is relatively clean and not soaked in linseed or motor oil as is common in old firearms. If it was saturated in oil, I’d have to remove that first with a slurry of Whiting (powdered chalk) and mineral spirits under a little heat to draw out the oil. If the oil had deteriorated the inletting to the point of punky softness, I’d have to let in new wood like I’m doing at the toe chip and reinlet the stock.
I apply the thawed epoxy from yesterday to the inletting under gentle heat, then thicken the epoxy with a high-adhesive thickener and apply the thick paste…
…then coat the hardware to be bedded thoroughly with paste wax, taking particular care to fill any holes or voids that might get epoxy extruded into them, preventing easy removal. Toy-store modeling clay applied before the wax fills larger voids nicely.
Apply epoxy to any missed cracks and voids that still need a little epoxy filler
Then the hardware is bedded completely, to include driving any screws…also thoroughly waxed…cleaned as necessary with vinegar…and allowed to cure….
When cured, the epoxy repairs are taken down to the original surface of the wood finish, but not beyond, with a fine saw and fine, single-cut files in crossfiling and drawfiling mode. I’ve really come to like these Japanese-style pull saws for flush cutting, as they have no set to the teeth that scratch adjacent surfaces. To remove the bedded hardware from the freshly-cured epoxy, simply back out the screw attaching it from behind, and give the screwdriver a light hammer tap while still in the screw slot. If I didn’t use enough wax and my hardware is hopelessly stuck, then 115 degrees or so of heat applied to the metal by a soldering iron will free it…the piece may or may not have to be rebedded afterwards, as epoxy is often very forgiving.
The hardware is reattached for final filing of any repairs close to the edge to serve as an index and prevent roundovers. This butt plate will be refinished, but to preserve a metal finish you desire to save, cover it with masking tape to protect from the files. I then finish sand only the repairs with 180 grit wet-or-dry paper, dampen lightly all the new wood surfaces to raise the grain, and sand the repairs again using 220 grit. There is a tiny gap remaining at the tip of the butt plate I’m not happy with…I can either bed that in epoxy or bend the buttplate slightly to close it. As this rifle will see more hard use in its life, I choose to bed the entire butt plate and repeat the procedure I used for the receiver tang above.
03-10-2004, 03:43 PM
Now for the more difficult task of equalizing the color. For this and other finishing inspections, sunlight is essential…note that the original finish on the forearm is age-darkened, medium-stained Black Walnut with a hint of red. I’ll not attempt to change that color or damage its original finish, but match it in the buttstock. I don’t detect any prior repairs, but for some reason the buttstock was stripped, removing color but not the grain filler, exposing a streak of sapwood along the comb, and coated with a clear finish by someone unskilled, as there are some runs. Fortunately, it was not heavily sanded.
There is some surface damage to the forearm finish and a large dent, so I carefully remove only the deteriorated varnish layers to save the age patina beneath…and to remove the embedded dirt…with Formby’s Refinisher and 0000 steel wool. Formby’s is a proprietary product but seems to be trichloroethylene-based, so wear gloves. Used with care, it is excellent for removing one layer of old finish at a time. A light touch is all that’s required with traditional finishes.
I also attempt to do the same with the buttstock but discover it is harder, modern polyethylene….my bane….and have to resort to methylene chloride stripper and 0000 steel wool. Coarser abrasives and dipping are faster but will remove the grain filler I am trying to save and add a lot of additional work to the process. With a bit of time and elbow grease, I’m able to remove the poly sufficiently to take stain without damaging the filler severely. As I remove old finish, I purposely rub it into the new wood repairs to distribute the old color to the new wood as much as possible. For this reason it is critical that the old finish not be removed until after all repairs are complete.
Then I neutralize the chemicals with a wash of turps and evaluate the color match again. At any time during finishing, a light wipe of turps will allow the surface to appear as it will with the final varnish.
Wiping off the turps, I then steam out the dents with a hot soldering iron pressed against a sopping-wet rag applied to the dent. I do this several times until the dents are raised as far as the steam will take them…any dents remaining will be filled with the final finish material. More dents remaining after steaming mean more coats of finish will be necessary to fill them.
A coat of medium walnut oil stain is applied to the sapwood areas and allowed to dry, feathering the edges with a fingertip as it sets up. I rarely use finishing materials direct from the container and prefer to mix them in clean containers with a drop of heavy metal Cobalt or Japan Drier added. The added drier is important in the first coat of stain or varnish that has to amalgamate chemically with the surface beneath, and also in a cold shop like mine.
Alcohol-based “spirit” stains and aniline dyes can also be used, and are clearer than pigmented oil stains. I find, however, that they aren’t as easy to blend when restoring an old finish with alternating layers of varnish and stain, and they don’t hold up as well to fading from exposure to UV light.
Next I even out my coat of now-dry stain with 0000 steel wool, then add a light coat of “French Red” walnut oil stain to the buttstock and apply the first light coat of tung oil varnish to the forearm. This finger-applied varnish is clear, weather resistant and does not darken in UV light…but most importantly; it is relatively soft and flexible and will not chip. Exterior “oil” finishes like this and other polymerized tungs, “Truoil” and “Linspeed” which are linseed-based polymerized oils, are not oils at all but soft varnishes. They wear through with hard use, but their major advantage is that they are easily renewed with a 0000 steel wool scrubbing and more topcoats, preserving the priceless age patina beneath without the necessity of ruining it with the strippers necessary for traditional resin varnishes, lacquers and polyethylenes.
I touch the buttstock up in spots with both walnut and red stains, feathering carefully and evaluating in the sunlight, until I am satisfied with the color match, then I begin finish coating the buttstock in addition to the forearm.
03-10-2004, 03:43 PM
For a perfectly level finish, each coat of varnish is rubbed back to the grain surface of the wood. The finest steel wool is used again followed by a paint-store tack rag and a final buffing with a lint free cloth, with extreme care used to brush wool particles from grooves and recesses. This doesn’t allow much buildup, but it fills minor pores and imperfections missed and also toughens the final surface of the finish. To minimize dust contamination, a simple, open drying box with canvas drape and light bulb can be used. I have a couple of them. You don’t see them, but in this finishing session I am doing 6 gunstocks at once…far beyond the capacity of my drying boxes… so I cease using machines for an hour prior to finishing and make that my last task of the day, placing a space heater directly beneath the improvised drying rack to speed them reaching the tack-free stage.
Once I’m satisfied I have the buttstock’s stain coats thoroughly sealed…usually with two coats of these thin, finger-applied varnishes…I do the final color stage to hide any glue lines and remaining imperfections. This step clouds the finish and is used sparingly. In the sunlight, I mix Raw and Burnt Umber and Burnt Sienna oil pigments to achieve an exact color match, adding a couple drops of drier as I mix. Applied sparingly and feathered with a fingertip to the freshly-rubbed finish, this hides obvious glue lines well if I feather carefully to avoid the painted-stripe look. Apply too little rather than too much. The excess goes in the freezer in case another application is needed after the next finish coat.
The final coats are applied and allowed to cure. How many coats? As many as it takes to fill all the minor voids in the surface….usually 6-8 coats. Curing depends on finish material and temperature, and can be from two weeks to several months. Tung cures more quickly than many resins and a couple weeks is all that’s required. The piece can be used while it is curing.
As this is a replication of an aged and slightly worn factory finish, I merely use fine steel wool lubricated with carnauba wax to rub out the finish. I could rub out the wear areas harder than the flat areas of the stock to replicate handling wear, but this finish base will last the life of the rifle with proper care, and a couple seasons of normal use will make it look “right” better than I can.
The color match and glue line hiding came out decently…for the price of about three hours of cumulative shop time over the course of a three weeks.
“When we build, let us think that we build forever. Let it not be for present delight nor for present use alone. Let it be such work as our descendants will thank us for; and let us think...that a time is to come when those (heirlooms) will be held sacred because our hands have touched them, and that men will say, as they look upon the labor and wrought substance of them, ‘See! This our father did for us.’ “ --John Ruskin.