Wood repair: tips for dealing with small imperfections
We’ve all been there: the shop is too small, your project rather large, and at some point you damage a visible surface with a ding, dent or gouge. Or you notice a crevice on a stile that appeared out of the blue after assembling a door frame. It is maddening, but it seems all too common, and knowing how to repair the damage can mean the difference between salvaging the work you’ve done up to this point or making a replacement piece.
When choosing a method to repair the damage, you will need to take into consideration a number of factors such as the degree of the damage, the nature of the damage and the final finish to be used on the piece. If you are faced with a simple ding or dent that has crushed some fibres you might be able to use a damp cloth and iron to steam the damaged area.
Filler dried and sanded
Chipout in dovetail
Filler dried and sanded
Wood Fillers are Workshop Essentials
If steam doesn’t do the trick, then it’s time for some stronger medicine. Commercial wood fillers are available in many different formulations and your final success will require that you choose the right product for the job. When selecting filler you will have to choose between a lacquer base, an oil base or a latex (water) based product.
Lacquer based fillers offer a quick drying time and are compatible with most finishes, but they dry hard and have a tendency to shrink and crack. Oil based fillers often do not dry completely and can cause problems when subsequent film finishes are applied. Always be sure to check that the filler you plan on using is compatible with the finishing products that you plan to use.
Latex based fillers offer fast drying times without the disadvantages associated with lacquer and oil based fillers. The new stainable fillers are compatible with a wider range of finishes. If the area is deep, clean away any loose material and smooth it with some sandpaper. Apply the filler in several thinner coats and leave it for the required drying time between coats. Applying the filler in one thick coat will make it almost impossible for it to dry, and as it dries it will shrink and crack in the center. After each coat has dried, sand it smooth and repeat until the original profile has been regained.
Most commercial latex fillers on the market are either stainable or are available in pre-tinted colours. The Elmer line of fillers is available in eight colours ranging from maple to walnut, making it possible to come close to matching wood colour. However, you can blend filler colours to get an even closer match. The un-tinted stainable fillers contain wood as the binder that helps to absorb the stain.
Use Epoxy for Large Voids
Larger voids and damaged areas can be repaired using a two-part epoxy mixture. The epoxy will dry hard without the risk of cracking or shrinking and it can be machined like wood. When mixed, epoxy dries to a clear finish, which can be unappealing on a finished piece that will be stained. To avoid this the epoxy can be mixed with tints and pigments from an art supply house or well-stocked paint store. Mix up enough of the epoxy for the repair and add any tint that is required, then carefully apply the epoxy to the area with a knife or wooden stick. Using epoxy is messy and difficult to clean up, so work accordingly.
Repairing a Dent With Steam
You can repair small dents on an unfinished surface using a clothes iron and a wet cloth. Soak a towel in water and wring it out – it should be wet but not dripping. Clamp the piece to your bench in a convenient location. Set the iron to the highest setting and let it heat up. When the iron is hot, place the damp cloth on the damaged area, a single layer thick and press the iron to the cloth. Let it steam for a second or two and remove the iron. The water will have soaked into the surface of the wood and as the iron converts it to steam, the crushed cells will expand. Often this will eliminate the need for wood filler. After the piece is steamed it will need to be sanded again because the steaming will have raised the grain in the area.
Sawdust as Filler
Combining sawdust and glue is one of the most common ways of filling an imperfection. Use coarse sandpaper (50 grit) or a fine-toothed rasp to make enough sawdust from the same type of wood you are repairing. Then add glue to the sawdust and mix until it is the consistency of putty. Press the wood filler into the void. A toothpick works well for narrow spaces. Let the filler dry for a couple of hours, sand lightly, and then apply your finish. Glue and sawdust filler works best when used for very small imperfections or if the finishing application will be a solid colour.
Alternatively, sawdust and a finishing product can be used to hide some imperfections. For very narrow crevices, or hairline cracks no wider than the thickness of a piece of paper, pour a small amount of the finish on a piece of 100 grit sandpaper and sand the piece. The sawdust and finish will mix as you sand and push the slurry into the space. If the space is larger, try mixing the finish with the sawdust, then fill the space. You may have to dilute the finish before mixing it with the sawdust. Since sawdust consists of broken wood fibres, it will absorb the finish more readily than the solid wood. The filled space will be darker and more noticeable. This method works best on softer darker coloured woods.
For Narrow Crevices Use Splinters
If you have a narrow, wedge shaped crevice, try filling it with a wood splinter. Shave or split thin splinters from a scrap piece of wood from your project. Squeeze wood glue into the crevice and insert the splinter. Then use a flat head screwdriver or other relatively dull tool to push the splinter firmly in place. Try not to break the wood fibres, as they will accept the finish in a manner more consistent with the adjacent wood. This method works best with larger gaps, harder wood, and lighter coloured wood.
Tips on Using Fillers
Installing finished cabinetry is a delicate process and in spite of the best precautions, you may still end up with a minor scratch or two to touch up afterward. Attaching the final trim pieces with brad nails will leave holes to be filled, and even the holes made by fine 23-gauge pin nailers can sometimes benefit from a touch of filler. In this situation, because you will be dealing with finished cabinets, it is advisable to test the filler on a sample of stained wood to be sure that the two are compatible before committing to the visible surfaces. Some fillers can act as a solvent when in contact with certain finishes and may soften the finish in that area. Over the years life will leave its mark behind on doors, baseboards, and furniture (such as table and chair legs) in the form of dings and gouges. As most trim and older doors are painted, these blemishes are easily repaired using paintable carpenters wood filler. Sand the area to be filled to remove any rough and loose material; this also provides a key for the filler to adhere to. Use a putty knife to apply filler to the damaged area in shallow increments, allowing each layer to dry completely before sanding it and applying the next. When the surface has been levelled and the filler has dried completely, feather it in with the surrounding area and paint it. On wood furniture try the Tinted Wood Fillers, which are sandable, stainable and come in six colours.
When you are filling finishing nail holes and minor scratches on finished cabinetry often a simple crayon shaped stick of filler is all that is needed. Rub the tip of the stick into the defect to deposit some filler and then smooth it out with your finger.
When working with a damaged area, it is best to try and limit any additional damage that the filler, or its application may cause to the surrounding area. If you are working with an open grain wood such as oak and you get filler in open pores, you will find it almost impossible to remove without sanding or planing to fresh wood. To avoid damaging the surrounding area, cut a hole the size and shape of the defect in a piece of packing tape or painter’s tape. Packing tape is thinner but can be a bear to work with; painter’s tape is easier to work with but its rough surface is thicker. Place the hole over the defect and allow the tape to protect the adjacent areas; apply additional pieces if required. Use a putty knife to apply the filler to the defect and when the repair has been completed, remove the tape and sand the surface to a final finish.
The human eye very easily detects regular shapes such as squares and circles when set in a natural environment. The development of camouflage techniques has reflected this with irregular shapes used to blur the sharp outlines of an object such as a vehicle. Use this technique when repairing defects in your wood. Filling a defect that has a round shape or straight lines will be far more noticeable to the eye afterward than a repair in the shape of an oval (or a biscuit).
There are times that you will be faced with the need to repair a special piece of wood that contains a range of colours. This can be a challenge if the scratch crosses several colours; commercial fillers are of one colour and mixing fillers of different colours in a small repair can be tricky. In this case, choose the filler that most closely resembles the main colour in the piece and fill the damaged area as outlined above. When the filler has dried and has been sanded for finishing, use some artist pencils that match the colours to draw in a grain pattern to fool the eye before applying the final finish.
The key to using a shop-made wood filler is experimentation and experience. Test your filler on a scrap piece of wood first. Remember to record what you did and what worked best. Then share it with your fellow woodworkers – we can all use a tip or two in our quest for perfection.
Caulking as Filler
Most trim in houses is painted white, and as woodworkers we have the ability to use a table saw and router table to make any form of trim we desire using MDF. It doesn’t matter if the trim in your house is the plain variety or something a little more elaborate, chances are there will be gaps along the drywall and in the mitres around doors. Use painter’s tape to mask the area off and then run a small bead of white paintable latex caulking along the joint. Use your finger to create a smooth transition between the two surfaces. Closed joints can make the difference between a mediocre trim job in a house and a great one.