Repairing Dents and Gouges in Furniture
There are three levels of damage in finished woods:
In the clear topcoat,
In the coloring (stain, tinting toners, glaze, and/or shading stain), and
In the underlying wood.
Unfortunately, most damages are found in all three levels. And, since so many types of finishes are used today, it's difficult to know exactly how the existing finish was started or completed.
When viewing repairs from different positions the lighting can cause refraction that distorts the repairs, making them appear obvious from one direction but not others. The type of lighting can make the restoration look unnoticeable from one position, while at another angle the repair is more visible. For that reason, transparent repairs should be done in the same position where the piece will remain. If the damage is on a vertical plane, repair it in that same place. If the damaged area is perpendicular, then do your work in that position. The goal when working on see-through repairs is that completed restorations always remain transparent as possible.
Several techniques are used for transparent repairs, but this article will concentrate on two of the most common methods. The first one is where an impact has depressed the finish and the wood. The second procedure involves the deeper types of damage, where portions of the actual wood were gouged out or torn on the furniture going below the surface finish and coloration.
Because all repairs in transparent finishes are tricky and problematic there is basically only one chance to do it right, so the repairer must observe both the damage and the type of finish being repaired. As with all repairs, start by de-waxing and cleaning both the damage and the entire surface to be worked on.
Repairs on "Dented" Wood
In this type of damage the underlying wood has suffered an impact, putting a dent or depression in both the wood and finish; everything else is otherwise intact. The wood fibers are not torn.
Dents can be too shallow to allow successful repair. In such a case either the surrounding clear finish can be abraded to be more level or the dent made deeper to allow a reasonable repair.
These types of damages need to be clear-filled to keep the repair transparent. If any color touchup is needed, do it first. Determine if the clear coating is amber-colored or water-clear by lightly sanding in an inconspicuous area and checking the color of the resulting sanding powder.
For compatibility reasons, the repair process is easier when the same resin is used as the original coating on the furniture, so fill the damage using the original coating if it is known what it is. If not, then consider the resins of other coatings, including shellac, lacquer, acrylic, varnish and polyurethane.
Whenever you're working on coatings that are extremely hard, highly durable and have a high-level chemical resistance, also consider one of the two-component resins with similar characteristics. Keep in mind that reactive and two-component fillers are harder to sand than the evaporative coatings, and there is little or no shrinkage after these types of fillers are coated. Also, harder fillers can be a problem when used on the softer coatings. Because so many different coatings are available, it's important to test the resin and coating to get a working knowledge of which fillers work best, depending on the coating being repaired.
Drip the resin into the damage with an eyedropper, a good tool for certain filling. If the filler is an evaporative coating, overfill the damage to allow for shrinkage from the solvent's evaporation. If the resins are reactive there should be minor shrinkage, so fill only slightly above the surface. (Remember that the more resin being applied, the more that has to be removed.) Check the fill for bubbles, using a pointed instrument or the heat from a hair dryer to release any that are found, and then allow the resin to harden.
Put masking tape around the filled area and use a sharp scraper, razor blade or sandpaper to level the filler. Start sanding or scraping on the masking tape to level the fill, rather than on the coating, to avoid over sanding the filler. Use sandpaper that will cut the filler without leaving deep scratch marks, and never use clogged sandpaper, which can leave scratches in the filler and surrounding coating. Level the filler down to the masking tape, and then remove the tape. If the tape sticks, use mineral spirits to remove it. Once the surface is cleaned, it's ready to sand the fill level. When the filler has hardened, apply a few compatible clear coats over it to join the original coating, filler and new coating so that all final sanding is on the new coating.
The final coating can be sprayed, brushed or padded on the surface, depending on the type of finish being used. When done, any sheen adjustment can be done by rubbing out with nylon rubbing pads or polishing the coating with a rubbing compound.
Repairs on “Torn” Wood
For the deeper damages down into the wood, start by using a sharp razor to remove any loose pieces of coating or wood splinters surrounding the damage, cutting the damages into an oval or other profile shape, as the cleaner lines are helpful in hiding finished repairs.
Sand the walls and edges inside the damaged area. The finer the sandpaper, the better the light reflection after the full repair. Smooth out the damage with finer grits of sandpaper or the higher-micron grades of polishing pads. This fine sanding the filler smooth and level to the coating's surface without leaving scratch marks in the filler or coating. (Remove any deeper scratch patterns with a finer sandpaper or polishing micron pad until the scratches are gone.)
In this type of transparent repair the goal is to not fill the deeper damages in the substrate the same way you would in other finishes–fill only to the top of the wood line that is below the surface finish. This is where the wood ends and the coating starts; the space between the base filler to the top of the surface will be for the coloring and a clear filling. Use any coating resin as the base filler, or use any conventional filler, including wood powder fillers, wood dough and putty, epoxy sticks or burn-in sticks. When the base-fill hardens, use the tip of a folded piece of sandpaper to sand it level and smooth.
Start by brushing the top of the base filler with a gold bronzing powder and a binder, such as shellac, to add some iridescence to the repair. When dry, add coloring to match the wood, following the wood's pattern by inserting grain lines, distressing or any other distinguishing markings. Aniline or other dye stains are good for coloring because they're transparent and allow light to pass through. Using pigmented colored powders, they must be thinned to avoid "painting" in the color. Transparency is necessary to allow some of the gold's iridescence to show through.
Next, clear-fill any remaining space with either a single resin or two-component filler, depending on what type of coating is on the piece. As before, check to see if the clear coating on the piece is water-clear or amber with a sanding test in an inconspicuous spot. If color is needed in the clear filler, add dyes or reduced pigmented powders to maintain the transparency.
Again, remove any bubbles before allowing the repair to cure, and then level the repair with a scraper, razor or sandpaper. As before, put masking tape around the filler and sand or scrape on top of the tape, rather than the surrounding coating.
After the filler has hardened, a few clear coats over the filler will join the repair to the original coating. Follow the above sanding process going to the finest grits or polishing pads, then finish with a couple of clear coatings. If any sheen adjustment is needed, then sand, rub out or polish up to complete your repairs. This procedure is also used when clear coats succeed opaque colored base coats.
Practice these techniques on different species of woods to get the feel of each step. Start by making small damages, and then increase the size as the procedure is perfected.
Based on an article “Two ways to tackle the most difficult repair” by Mac Simmons in Woodshop News June 2003. We thank him for the concepts of his article.
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