How to Repair Wood Dings, Dents, Flaws and Knots

How to Repair Wood Dings, Dents, Flaws and Knots

How to get rid of these small problems, before they become big ones.

During the final smoothing of any piece of furniture, imperfections invariably appear. These can be simple dings and dents that are self-inflicted during moving the piece around the shop. Often they are defects in the wood such as checks, knots or bark inclusions. All of these problems can be dealt with fairly easily. Doing so saves a huge amount of time and sandpaper in the long run because sanding the rest of the surface to get below small defects is very time-consuming.

Steaming Dings and Dents

Dings and dents can occur from causes ranging from a hammer blemish to a collision with something sharp and heavy. It is easy to dent something you did not intend to hit while hand planing or by simply dropping a tool. How easy the repair is depends on the force behind, and the shape of, the object that causes the dent. Sharp object strikes are much more difficult to repair than blunt, round objects. Light strikes from round objects can sometimes be completely steamed out, but most need some sanding as well.

A common household iron is perfect for the task of steaming, and it will not be harmed in any way, although my wife was sufficiently skeptical that she bought me my own. A really cheap one will work for our purposes as we are simply looking for heat. Set it as high as it will go: the linen setting. Wet a thick piece of absorbent cloth (I use a piece of an old bath towel) and lay it over the dent. Place the hottest part of the iron over the cloth and press down firmly without touching the wood surface anywhere. Hold it in place for about thirty seconds. Check progress and, if necessary, repeat after again wetting the cloth. It may take three or four times. Steaming can sometimes completely remove a dent, but usually the swelling only undoes about 80% of the damage. If that is the case, sanding and/or filling will be necessary.

 I made three dents of increasing severity in this piece of cherry. Working from severe to moderate, I have applied steam.
I made three dents of increasing severity in this piece of cherry. Working from severe to moderate, I have applied steam.
Steam alone fixes Dent One, while sanding is hiding Dent Two. Dent Three will need filling, which I am doing with blond shellac flakes.
Steam alone fixes Dent One, while sanding is hiding Dent Two. Dent Three will need filling, which I am doing with blond shellac flakes.
Now that all the repairs are complete, I have applied a French polish to the plank and it is hard to find the defects. The knot looks natural.
Now that all the repairs are complete, I have applied a French polish to the plank and it is hard to find the defects. The knot looks natural.

Filling Partially Steamed Dents, Checks, Bark Inclusions and Dead Knots

It is possible to fill some serious flaws in a piece of wood, leaving a good-looking surface that no one will see as repaired. Depending on the situation and the size of the hole, I use either five-minute epoxy, shellac flakes or burn-in sticks.

Epoxy is great for a large dead knot which is either loose or has fallen out completely.

Most knots are dark in color, and many are black. I mix powdered color with the epoxy to get the approximate color I want. Here I am using lamp black because this cherry knot is black. If the hole goes through, put some masking tape on the far side. Now trowel in epoxy. If possible, more than fill the void as the epoxy will shrink as it dries. If there is still an indentation you will have to mix more and apply another coat.
Most knots are dark in color, and many are black. I mix powdered color with the epoxy to get the approximate color I want. Here I am using lamp black because this cherry knot is black. If the hole goes through, put some masking tape on the far side. Now trowel in epoxy. If possible, more than fill the void as the epoxy will shrink as it dries. If there is still an indentation you will have to mix more and apply another coat.
Sand to the desired grit and we have an effective repair that looks natural.
Sand to the desired grit and we have an effective repair that looks natural.

I use shellac flakes for small to medium blemishes, as well as small knots and bark inclusions.

If you use shellac as a finish, it is easiest to make it from flakes rather than buying it ready-mixed in a can. The can has a shelf life, and you get a much higher grade shellac in the amount you need by mixing flakes with denatured alcohol. I use a process of padding shellac called French polish. It is possible to get shellac flakes in about five grades, ranging from super blond to amber to a dark garnet color. I pick one that is as close to the color of the wood as possible.

The traditional way to apply shellac to a blemish is to heat a pallet knife with a shellac flake on it with an alcohol lamp. Once the shellac melts, simply trowel it into the defect. I found that it is possible to order a special tip for my Weller Soldering iron that works even better than a pallet knife. Intended for smoothing solder it is Weller part #6160. Here I am using it to burn shellac into a blemish. Shellac is a thermal plastic, viscous when heated and hard once dry, which only takes a couple of minutes. Build shellac higher than the surrounding wood and sand smooth once filled. You can also sprinkle some ground color into the shellac while it is still hot.
The traditional way to apply shellac to a blemish is to heat a pallet knife with a shellac flake on it with an alcohol lamp. Once the shellac melts, simply trowel it into the defect. I found that it is possible to order a special tip for my Weller Soldering iron that works even better than a pallet knife. Intended for smoothing solder it is Weller part #6160. Here I am using it to burn shellac into a blemish. Shellac is a thermal plastic, viscous when heated and hard once dry, which only takes a couple of minutes. Build shellac higher than the surrounding wood and sand smooth once filled. You can also sprinkle some ground color into the shellac while it is still hot.

 

The patched knot.
The patched knot.

Burn-In Sticks

Burn in sticks are easier than using shellac flakes, especially if you do not finish with shellac. They are what the furniture repair guys who come to your house in vans use to take the obscene words out of your tabletop after the stoats have been driven out to Toad Hall. They are a modern version of beaumontage, which, up till the mid 20th century, finishers made themselves by heating beeswax, resin (from pine trees), shellac and ground color till they liquified and mixed. Traditionally, the finisher heated a steel wire over an alcohol lamp, held it over the defect and touched the beaumontage to it; the beaumontage liquified and ran down the wire into the void. Today, you can buy burn-in sticks to match just about any wood or finish. They can be troweled in with a heated pallet knife or with special electric irons for the purpose.

Using an electric iron to apply burn-in stick to a void.
Using an electric iron to apply burn-in stick to a void.

Please give any and all of these techniques a try. It is best to do as much of the repair as you can before sanding. While your repair may look bad at first, sanding blends everything together, making it all but invisible. A second benefit to these techniques is that they are just as valid for repairing furniture or woodwork that gets damaged in day-to-day use. It saves you having to call the furniture repair guy, once you see the last of the stoats.

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  • Loonboy

    To get rid of these small problems before they become big ones is really useful to prolong the life span of our daily tools.

    http://www.cnc-routers.org