Wood Finishing and Repair

Preventing bubbles and "craters" in varnish

If not properly applied, wood varnish can develop bubbles that remain on the surface or pop to form craters. To prevent bubbling, never shake a container of varnish-stir it gently.

Bubbles also appear during rapid application with a foam brush. Another cause of bubbles: tapping the brush on the container to remove the excess after dipping in the varnish. If there’s too much varnish on the brush, gently press the brush against the side of the container.

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Wood filler and putty: the finishing touch to woodworking projects

For a perfect finish to varnished woodwork or other woodworking projects, fill all nail holes and voids. Voids disappear when filled flush to the surface with properly colored putty. Stain the wood first, then fill the holes with putty after the stain has dried. This enables you to perfectly match the color without depending on the stain to color the filler.

The quickest and least expensive way to obtain putty of the correct color is to mix your own. Buy small containers of putty in light oak and dark walnut colors. Blend small portions of each color until it’s the right shade. In some cases you’ll also need to blend in some red mahogany color.

Once you have spent several dollars on two or three basic colors, you can custom-mix a wide variety of shades. With oil-based putty in resealable containers, you’ll be set for years. Any custom-mixed putty left over can be stored with the original color putty without problem.

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Refinishing kitchen cabinets

Painted surface

If the old surface was painted, you must remove the paint with a chemical stripper. For more information, see "Repainting kitchen cabinets" in the "Paint and Drywall Finishing" section.

Stained/varnished surface

If the old surface was stained and/or varnished, you can refinish the cabinets just as fine furniture is refinished. You can either remove most of the varnish/stain with a chemical refinisher, or you can just clean the surface well.

In any case, first take the doors off the cabinets and remove handles and other hardware. This will make the project easier, and the results will look more professional. Lay the doors flat when you work on them.

If the only damage to the finish is dark stains around the door handles, you can simply clean these areas. Try using 3M synthetic steel wool pads instead of real steel wool. The pads hold together very well. They won’t poke your fingers or catch on the wood grain.

Scrub the stains with a pad dipped in mineral spirits, turpentine, or paint thinner. Then lightly scrub the whole surface, cleaning and dulling it so the new finish will stick.

Follow safety precautions. Wear protective clothing and make sure the work area has good ventilation. All of these products are flammable; some are extremely flammable. Follow any other safety precautions on the label. Some refinisher chemicals contain methylene chloride and may cause blindness.

After the surface is clean and the dark stains are removed, apply a clear wipe-on oil finish as described below under "Clean finish."

If you ne ed to redo more than just a few stained areas, chemical refinishing is necessary. A refinisher is a strong solvent cleaner that dissolves and removes part of the old varnish. When choosing which refinisher to use, visit a quality paint store or paint department where you can get good advice. Many companies offer refinishers like those made popular by Homer Formby.

As chemical refinisher removes the finish, it also evens out the color of the wood and stain. You work in a small area, scrubbing the finish with steel wool or a 3M synthetic steel wool pad. As the steel wool becomes clogged with dirty finish, you rinse the pad in more refinisher.

Once you’ve scrubbed the whole surface, it will be smooth and evenly colored. If not, wipe down the whole piece with clean refinisher and clean steel wool in long, overlapping strokes. Most of the stain color will remain, and the wood will be very smooth.

Clear finish

After cleaning or refinishing, apply an oil-based wipe-on clear finish such as Minwax Antique Oil Finish, tung oil, or General Finishes Royal Finish (my favorite). All are low-odor and can be applied with a rag. Most are available in either glossy or satin finish. Using several coats will produce a thicker finish.

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Fixing scratches in stained woodwork

"Quick and simple" rarely describes repairs to wood finishes. But you can try these tricks.

When scratches appear lighter than the surrounding dark-stained woodwork, it usually means either that the scratch goes through the stain into the wood or that the varnish is flaking off.

Restoring the clear finish

Inspect the scratches carefully. If you can see flaking varnish with dark-stained wood underneath, you just need to restore the clear finish. Rub the loose varnish with fine steel wool or fine synthetic steel wool until you have removed the flaking varnish and slightly roughened a small area of the finish surrounding the scratch.

With the tip of rag, a small brush, or even a cotton swab, apply a thin coat of a wipe-on oil finish like General Finishes Royal Finish or UGL Wipe On Tung Oil. These finishes work well because they will bond to the existing finish. Apply finish to the damaged area only. You may need several coats to hide the scratch.

Re-staining the wood

If bare wood is visible at the bottom of the scratch, you need to re-stain the wood. To remove damaged varnish, lightly roughen a small area around the scratch with sandpaper, steel wool or synthetic steel wool.

Find an oil-based stain that is a shade lighter than the wood finish. Stain the bare wood with a very small amount of stain on a rag, brush or cotton swab. If the color is too light, apply several coats. Rub away excess stain with a dry rag. If the wood becomes too dark, use a rag moistened in mineral sprits to lighten the wood. Then select a lighter color stain and continue.

Several companies have simplified this repair process by putting oil-based wood stain into marker-like containers. You just rub the stain marker on the scratch. I suggest you start with a stain color that is lighter than the original finish, because torn and scratched wood fibers will absorb stain quickly and darken quickly. You can always apply a second coat if the color of the first coat is too light.

Once the color is blended, patch the clear finish as described above and apply a wipe-on oil finish.

An oil finish is generally a good choice in refinishing, except over several coats of hard finish (see below), where it will just lie on the surface without hiding the scratches. Oil finish may work as a top coat over old varnish that has been cleaned or partially removed with refinisher chemicals.

Hard finishes

If the original finish was coated with polyurethane or urethane (hard, durable finishes typically used on tabletops, for example), scratches are difficult to repair. Recoating the whole surface won’t work. The new coat may not adhere and might even magnify the scratches.

For small surface scratches that have not penetrated the stain or changed the color of the wood, carefully sand out the imperfection with 600 grit wet/dry sandpaper. Wet the sandpaper with water or lemon oil, and gently sand the damaged area. When you’ve removed the scratch, buff with 0000 steel wool and paste wax to bring back the shine.

You could also try oil finish to touch up a small scratch in polyurethane, but there are no guarantees of how the oil will stick or blend into the surface. However, you have little to lose by trying this method. Use an artist’s brush to carefully fill the scratch, one thin coat at a time.

When a scratch has penetrated so deeply that a color difference is visible, you must fill the scratch and color the wood with one of many available products: oil stains, stain pens, or touch-up sticks. Use an artist’s brush or toothpick to fill in tiny areas. After the material has dried, buff back the sheen with 0000 steel wool and paste wax.

If the piece is an antique, you may have to live with the scratch. You might also consult a furniture finish repair company.

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Refinishing wood furniture

When refinishing furniture, once you’ve stripped off the old paint and sanded the wood, you have many, many options for finishing the surface. My preference is an oil-based stain and an oil rub-on finish. Visit a local paint store to review your options. Read the literature offered there.

I like oil-based stains because they penetrate the wood and are easy to control. I usually select several colors and test them before I do the whole project. After you test a small area, also test the clear finish over the dry stain. The finish will darken the stain color. Minwax, Zar and Sherwin Williams are brands I have used with success.

For a clear finish, try wipe-on or rub-on oil finishes like General Finishes, Zar or Minwax brands. These finishes are applied with a rag and have low odor. You can create any type of sheen or depth of finish. Applying more coats produces a deeper, glossier finish.

With wipe-on finishes, I like to apply several coats and allow the finish to dry fully. Then buff the finish with 0000 steel wool or a synthetic pad to remove all surface imperfections. Apply a final thin coat for a perfect finish.

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Use stripper pads, not steel wool

For aggressive removal of tough paints or buffing between coat of a clear finish, throw out your steel wool and use synthetic pads instead. I recommend a stripping pad made by 3M. This pad, about 4" x 11" and made of woven synthetic material, is designed to be used with chemical strippers. It doesn’t fall apart like steel wool and will not poke through your gloves or stick in the wood grain. You can find this pad at most hardware and paint stores. It looks very much like the Scotch-Brite scouring pads used to clean your pots and pans.

3M also makes a synthetic steel wool in grades to mat ch regular steel wool. You can remove rust, buff between coats, strip paint, or buff a final coat effectively with a synthetic pad.

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Stripping paint from wood pores

Oak, walnut, ash and other woods have wide pores, and it is difficult to remove old paint from these pores. Try these methods.

The first method is to spread a coat of chemical stripper, allow it to work the surface for several minutes, then scrub with a fingernail brush, a brass wire brush, or a 3M stripper pad.

The second method involves coating the area with a 50-50 mixture of shellac and alcohol. Let this dry on the finish. When you strip it off (it’s easily removed), small particles of paint that have bonded to the shellac will lift out of the pores.

Finally, if you plan to stain the oak, remember that staining may cover some of these small paint particles. You’ll need to experiment to see how well the stain covers. I have use darker stain to cover paint I could not remove.

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Refinishing a damaged front door

Many homes feature a beautiful wood front door that is stained and varnished. In time, though, the varnish begins flaking and peeling, especially if there’s no storm door.

Sunlight is the culprit. Ultraviolet (UV) rays attack the cellular structure of the wood under the varnish, giving it a "sunburn." Varnish can’t stick to damaged wood. UV rays also damage the clear finish.

The best solution is to paint the door. Paint has coloring pigment that blocks UV rays and protects the wood. But if you really like that stained and varnished look, it requires a little work.

First you must sand, scrape or strip the damaged finish. Where the finish is in good condition, you must sand and roughen the surface.

How far you go with the refinishing depends on the condition of the door. If more than 25% of the finish is damaged, your best bet is to chemically strip the door and start with bare wood.

For a final clear finish, look for a UV-resistant varnish (often called spar varnish or marine finish). The finish is expensive and may only be available in a gloss formula. Follow the specific instructions for your varnish, and don’t forget to finish all six areas of the door (front, back, top, bottom and sides).

A final option would be to install a storm door to protect the wood door. There are attractive storm doors available that are mostly glass so your wood door can still show through.

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Removing stains from an oak floor

Refinishing oak floors is just like refinishing oak furniture. You can repair any type of imperfection without complete sanding (or stripping) and refinishing. However, often floors are sanded and refinished because th is is the easiest route to a perfect new finish or because the homeowners want to lighten the whole surface. You need to decide whether repair or complete refinishing is in order for your floor.

If there is a light or faded area, try rubbing the spot with furniture refinisher on a steel wool pad. The strong solvent that will soften the existing clear finish and spread around a mixture of softened varnish and stain. This may even out the color variances. It might also lighten the whole surface as the old, darkened varnish is removed.

For dark stains, clean with a 50-50 solution of laundry bleach and water. Stains that disappear quickly were just surface mildew. Any remaining dark spots are water stains that have penetrated the wood. To remove these, sand the area or bleach it with wood bleach. Wood bleach is available at paint and hardware stores. It lightens the oak, turning it almost white.

After bleaching, the grain of the wood will be raised and rough. Smooth with sandpaper and then stain the area with an oil-based stain to match the original color. Finally, seal with the finish of your choice. I think wipe-on oil finishes are a good option for repairs.

You will need to be a bit of an artist with the stain color and final finish to blend in the color and gloss. Always start with a stain lighter than the final color you want to achieve. You can always add more stain or a darker color stain, but it is difficult to remove a dark stain color once it’s in the wood grain. Also remember that the clear finish will make the stain color appear darker and richer.

You can see why floors are often re-sanded to remove imperfections. All stains, scratches, and damaged finish are removed with sanding, leaving the surface flat, smooth and ready for a new stain and clear finish. Sanding is the only way to ensure a like-new finish.

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Safe finishes for children’s wooden toys

The Toymakers line of finishes and dyes is made specifically for wood toys and is non-toxic once cured. The dyes are tinted with food coloring additives. The manufacturer claims that the finish is convenient to use and has a professional appearance. The clear finish is applied like an oil-based finish and has the look of high-quality varnish. The dyes com e in four bright colors.

You can order the Toymakers finish by calling 1-(800)-279-4441. It’s also available at some woodworkers’ stores.

Several other manufacturers sell finishes that are safe when cured or dry. General Finishes is one such brand. You can also buy a special finish made for salad bowls and wood kitchen utensils. These clear finishes don’t build up on the surface.

Lead is not used in paint anymore, but you should carefully read the safety precautions of any finish you select.

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No need to oil or "feed" wood finishes

Despite what the advertisements say, lemon oil and similar products do not "feed" a wood finish. Lemon oil, a solvent-based cleaner, merely cleans the surface. The finish looks shinier because it’s cleaner. Some products identified as lemon oil also contain furniture polish, which may further improve the appearance of the finish.

Check the label of the lemon oil container and you will find that it contains petroleum distillates. These oil-based cleaners can effectively remove built-up oil, dirt, and wax, but they don’t oil the wood. It’s a fallacy that lemon oil or other polishes feed the wood by returning oil to it. Most wood does not contain oil and never needs to be fed. Save the oil for the bearings on your furnace.

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