The first thing to know is that a finish makes a huge difference in how well your wood is protected, and how expensive and luxurious it seems even to trained woodworker eyes. Old finishes are often poor finishes, and many types of valuable antiques benefit from a professional restoration. The myth of preserving an old finish for value is just a myth – especially if the poor finish is allowing for deterioration of the wood.
There are two main types of finishes, film and penetrating. Of these, penetrating is either oil or oil and varnish.
The four most common types of finishes are:
Here is a description of all of these:
The longevity of shellac is wonderful. Through the 19th and 20th century it was favored highly and these finishes are often intact even today. It is an excellent protector against steam, as well as silicone, grease, crayons or wood resins. It is sometimes used as the first coat on wood before lacquer is added because of its barrier qualities.
For those with children, it is so safe that the FDA approved its use in pills and candy coating. Its solvent is denatured alcohol. For those with pets and children, this is the best choice of finishes.
It is weak to heat and water, and it has a short shelf life.
Oils are a very popular finish with woodworkers because they are very easy to apply and keeps the wood close to the original wood’s appearance. It is most effective when it is applied to a thin layer that penetrates into the pores of the wood. An oil/varnish blend is much more effective than oil alone. Of the many types of oil available, synthetic oils are superior to natural oils.
Linseed oil is probably the least effective wood finish on the market, but it was used widely to manufacture cheap furniture in the 1800’s. Many varnishes are sold as “oil” when they are not oil at all. Oil cures slower than other finishes.
It is one of the easiest finishes to repair because you can just wipe more oil over the top when it gets scratched. Howard’s Restor-a-finish sold here at Furniture Works is primarily designed for repairing oil finishes.
How to identify if your finish is oil:
Originally derived from the lac bug in ancient India, today Lacquer refers to a modern acrylic product that is the standard in gloss finish furniture today. It is strong, durable and makes for a beautiful finish.
It is highly toxic and flammable, breathing the fumes is dangerous and can affect the nervous system.
It cures fast and can be applied in all types of weather! It has the most excellent clarity and depth of any finish, and is considered the ultimate finish ever since it was developed and introduced in the 1920’s.
One problem with lacquer is that plastic migrates into lacquer, deterioting the finish, so you shouldn’t keep plastic in close contact with it for extended periods of time.
There is a big difference between oil and varnish. Varnish is made by cooking oil or different mixed oils with resin, synthetic or natural. The heat causes oil and resin to combine chemically, forming a new substance. It cures faster than oil. Varnish forms a very hard surface, so that it can be built up layer after layer to achieve a thick, hard and beautiful finish that protects the wood from most scratches. A thin coat of varnish does little for the wood. Oil and varnish are compatible, so they may be mixed. Oil reduces gloss and makes the finish cure slowly.
Varnish is often sold as “tung oil” on so-called “oil” finish. True linseed and tung oil have a distinct smell. Once you smell it you know what it is, as they both have nutty smells, tung oil being sweeter than linseed oil.
Oil and varnish blends cure slowly, they can take hours to become tacky, so they are prone to dust contamination. Wiping varnish becomes tacky in 20 minutes depending on the humidity, and it cures hard. Oil varnish blends will be soft enough to dig a fingernail into, especially if the finish is thick
If the finish is wrinkly and thick, it means it had more than 10% oil in the varnish.
Over time, varnish turns yellow.
Water based finishes are resistant to scuffs and do not yellow. They don’t have as many problems with fumes and they are not a fire hazard. They are washed out and bland looking on dark woods and are very weather sensitive during application. They raise the grain of the wood. Lately they have become popular on furniture that needs a milky or distressed finish. It’s not completely non-toxic, like latex paint, you will start to feel light headed and dizzy working in a closed room with it. However, it is much less toxic than lacquer.
A lot of the strange milky white and grey finishes you see on World furniture is water base. When you do a “wash” with latex paint that is a water base finish.
A few wood tricks:
All finishes need to be kept out of strong sunlight if you want them to last longer. UV light is very destructive. Even indoor light will eventually break down a finish. All glass does block 80% of UV rays, so it does help some. To protect against deterioration, you should use a little paste wax or furniture polish.
You can steam out dents in wood if the fibers are still unbroken. It’s not 100% effective but it almost always works. Put a drop of water in a dent with an eyedropper or syringe. Let the water soak in a little. Add more water if needed to form a bead over the dent, then touch the water with a very hot object to tturn it into steam.
Let the raised grain dry before sanding it smooth. If the fibers are broken you will have to cut out the area around the dent and fill it with a patch of wood or other material.
Apply an oily substance like petroleum jelly or mayonnaise to the damaged area and allow it to remain overnight. The oil will sometimes replace the water because it has a greater affinity to the finish.
It looks like water damage but it cannot be repaired without striping and refinishing. It also often creates dents in the finish and in the worst cases, ripples of ugly crinkled finish, especially on beautiful deep mirror finish lacquer. You can apply alcohol to a shellac finish or lacquer thinner to a lacquer finish and correct the problem by redissolving the finish and letting it cure again. Its worth a try but usually does not work.
Nail polish, Permanent Markers and other Substances
For nail polish you should start with a plastic putty knife. You should be able to peel the nail polish off without hurting the finish. Apply a damp hot cloth to the polish to soften it.
Denatured alcohol will remove nail polish and permanent marker, but can also damage the finish, so use it carefully and remove it all quickly as soon as the stain is off.
0000 steel wool can be used to sand away the polish, without too much damage to the finish.
You can apply an oil like Howard’s Restor- a-Finish or Howard’s Feed N Wax to the wood to repair the finish color and shine.
Toothpaste is an old home remedy for removing permanent marker. It is slightly abrasive and works by scouring the surface.
WD-40 is also known to remove permanent marker stains.
As usual, follow up with Howard’s Restor-a-finish to replace the oils and protect the wood again.
Howard’s Restor-a-finish comes in dozens of wood finish colors, all available at Furniture works in a large bottle for $8.50.
For more in depth information on wood finishes, try the book “Understanding Wood Finishing, How to Select and Apply the Right Finish” by Bob Flexner.