How To Repair Scratches In Polyurethane Finish
Fixing Finish
Begin your repair by assessing whether but the film layer is damaged, or both the film and stain, exposing the wood. To test, wipe the damaged area with mineral spirits, as shown above, or simply a dab of spit. And so choose a repair based on the following:
- No change in color. Good news, the motion-picture show finish wasn't penetrated down to the wood fibers. Go to Fix #i.
- The color changes to lucifer the undamaged area. More adept news. Scratches penetrated the film finish, just the wood underneath either wasn't stained or no woods fibers bankrupt. Become to Set up #ii.
- The damaged area turns darker than the surrounding finish. This deep scratch broke forest fibers. Go to Fix #3 after reading the rest of this department.
Before starting the second or third fix, determine which type of pic cease was used. Peradventure you retrieve this for projects yous built. If not, bank check whether it's a lacquer finish by dabbing a hidden spot with lacquer thinner. If the cease softens, it'south lacquer. If denatured alcohol softens the finish, information technology's shellac. If at that place's no change and the piece is fairly new, yous probable have a water-based or polyurethane terminate.
If y'all don't know the stain, apply comparable colors to scraps of the same wood species until they match. Before starting all repairs, liberally apply mineral spirits with clean cloths to remove any built-up wax or spray polish.
Set #1: Paste wax for scuffs and shallow scratches
Cover up minor marring or scratches on a motion-picture show finish using paste wax tinted near the same color as your project. (Encounter Sources.) For a light scuff, utilize a soft cloth to apply the wax. For deeper scuffing, gently apply the wax with 0000 steel wool, equally shown below. Let the wax to harden, and buff information technology with a soft cloth to even sheen. If this produces a sheen that's unlike from the surrounding area (encounter "What is sheen?" on the concluding folio), wax the entire surface with a soft cloth.
This method has i drawback: Information technology doesn't repair the damaged area so much as cover information technology up. Should you later decide to repair the surface by dabbing on cease every bit in Set up #2 or applying another coat of finish, you lot'll showtime need to wipe away all traces of the wax with generous amounts of mineral spirits and soft, clean cloths.
Fix #2: Fill in a film finish
Some film-end dings are likewise deep for paste wax to cover, but they yet don't pause the wood's surface, as shown beneath. Using a fine-tip applicator (see Sources), dab a small corporeality of matching cease simply on the damaged area, as shown below. Lacquer and shellac patch easily with this method because the freshly applied finish partially dissolves and bonds with the topcoat. Go along dabbing on layers of finish until the patched area becomes level with the surrounding end.
Use a similar method to bear upon upwardly dinged polyurethane and water-based finishes, which don't redissolve earlier coats and level themselves. Dab on additional finish and allow it to dry. If there's nevertheless a slight depression after the finish dries, gently wipe the patch with 0000 steel wool and apply a 2d coat. If the patch stands proud of the surface, lightly sand it flush with 400- and 600-grit abrasives. Then restore the sheen of the patched area to that of the surrounding surface by sanding with progressively higher grits and, if necessary, rubbing compounds. A coat of paste wax besides can assistance blend the patch with the rest of the surface.
Gear up #3: Rebuild the finish from bare wood
If the mineral spirits wipe examination turned the scratch into a nighttime streak, the wood fibers accept been severed and the severed ends are soaking upwardly the mineral spirits. Deep harm requires all-encompassing repairs.
If there's simply one scratch and fibers don't protrude from the surface, first seal the damaged expanse by dabbing on a fifty-50 mix of film end and the appropriate solvent. And so restore color to the scratch by dabbing on the original or a matching stain using a fine-tip applicator until you match the color. Allow the stain to dry out thoroughly; so seal it by dabbing on topcoat equally in Set #ii.
For multiple moderate scratches, as shown below, consider sanding the impairment down to blank wood using 120-dust annoying. Sanding with a finer grit may produce a lighter surface when restained. Avoid sanding too much over the damaged area and creating a visible depression in the forest. For extensive damage, sand the entire damaged surface to blank wood and refinish information technology to match.
For smaller repairs, though, begin restoring the colour by wiping the blank wood with stain. Advisedly wipe the stain to the edge of the sanded expanse. Avoid staining the feathered border where the film finish meets bare wood, or you'll get out a darkened halo around the patch.
If the stain wipes on too light and the pores are not being filled to match the surrounding wood, scrape a minor corporeality of paint from the bottom of the stain can. Paint colors may vary from the dye in the stain (dye color doesn't settle as pigment particles exercise), so add together pigment carefully to a fabric moistened with stain. Then wipe this mixture over the previously stained area to darken it.
Using a back-and-along motion, add then partially wipe off plenty coats of stain that the color—while still moist—matches the undamaged surface. If you utilize too much stain, wipe it off immediately with mineral spirits and allow the surface to dry out. Build colour gradually rather than deposit too much at i fourth dimension.Allow the stain to dry completely before spraying or brushing on a topcoat to blend the sheen of the patch with the surrounding surface, every bit shown in photo beow. If necessary, recoat the entire surface for an even sheen.
What is Sheen?
Sheen refers to how much light reflects off a surface. To hide your repairs, you'll need to match the sheen of patched areas to the surrounding finish as carefully every bit you friction match stain color to the rest of the surface.
A sleeky end, similar the 1 correct, bounces more lite dorsum to your optics than a flat finish, which disperses the light. You can control sheen past choosing a flat, satin, semigloss, or gloss finish, each containing dissimilar amounts of flatting amanuensis.
That'due south non the only method, though. Y'all as well adjust surface sheen by how smoothly you rub out a film stop with abrasives, and that's what complicates repairs. During the repair, if you rub the damaged area with sandpaper or steel wool and alter the surface sheen, that calls equally much attention to itself as an off-color patch.
Avoid inconsistent sheen by using the aforementioned annoying on the patched area as you used to finish the surface when the project was built. Paste wax tin offset minor sheen differences, simply extensive repairs may crave refinishing the entire surface around the damaged area.
Tinted wax: Briwax in 9 shades, Woodcraft, 800-225-1153 or woodcraft.com. Fine-tip applicators: Microbrushes ranging from superfine to small brush sizes, Lee Valley Tools, 800-871-8158 or leevalley.com.
Source: https://www.woodmagazine.com/woodworking-tips/techniques/finishing/patch-wood-scratches
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