Restoring Oil Finishes
A QUICK HISTORY OF OILS USED AS FURNITURE FINISHES
The primary function of any wood finish is to preserve that wooden item against the effects of usage and of the environment. Secondarily, finishes are used to enhance the visual appeal of the piece. Virtually any oil can be applied to wood and will function at least temporarily as a preservative and perhaps as a beautifier of that item. However, most oils are not satisfactory wood finishes because the oil will either migrate too deeply into the wood and leave the surface dry and vulnerable to wear and weathering, or will not dry out and will leave the surface of the wood feeling tacky. The best oils for wood finishing are Tung oil and Linseed oil because they will actually harden fairly rapidly at the surface of the wood. Tung oil is pressed from the nuts of the Tung tree (Aleurites fordii) and Linseed oil from Flax seeds. In the areas where these plants thrive, these oils have been used as wood finishes for perhaps as long as two millennia. These oils can be applied in a raw (linseed) or a pure (tung) form or with hardeners or resins added to decrease drying time, increase surface sheen, or other performance features.
PROS AND CONS OF OILS USED AS FURNITURE FINISHES
In the comparison, we will focus on Linseed and Tung oils only and treat them as a group as much as possible and note differences where necessary.
WHAT CAN BE DONE TO RESTORE OILED FINISHES?
Oiled finishes require periodic re-oiling. The most common problem with oiled finishes is that they have not been maintained by periodic oiling. They begin to look dull and dirty. They can also become water-stained or scratched. Most problems with oiled finishes can be remedied by cleaning the surface and re-oiling. To clean, a quick wipe with a dampened cloth is alright, but using a water soluble cleaning solution and scrubbing the surface is very likely to cause blushing or other discolorations on the surface. Use of a mild solvent like mineral spirits (paint thinner) works well to clean the surface, but an even better cleaner is a mixture of mineral spirits and the oil itself. One half oil at most in this mixture, a 2:1 or 3:1 mixture works better. Scrub the surface with this solution and 0 or 00 steel wool. Scrape off stubborn paint, tar or other such materials with a knife blade. Wipe off the residue, allow the surface to dry and apply a new coat of oil.
Because oils penetrate the wood and stripping solutions remove what is on the surface, it can be a challenge to completely strip oiled surfaces. However, alkaline solutions like lye baths, will penetrate the wood and dissolve the oil. For thorough stripping of oiled furniture, immersion stripping systems which include a dip in a lye bath yield the cleanest results. We have such a system and are able to strip oiled items. Once the oiled finish is removed, then the piece can be re-oiled or finished with a modern finish if you want to avoid the routine maintenance required of an oiled finish. We have found that when oiling a surface, the best results are obtained with the following methodology. Plan to work on a surface or two at a time, depending on size. Thoroughly and liberally coat the surface with the oil finish. Keep the surface wet for approximately 30 minutes, rewetting sections that dry out. After 30 minutes or so, remove the excess oil and allow to harden for 24 hours or so. If you are oiling a new piece or one that has been stripped, repeat this process two more times for a total of three or more coats of the oil finish. For an even satiny appearance, the surface can be rubbed with 0000 steel wool after having been allowed to harden for an extra day or two.
CARE OF OILED FINISHES
The first step in caring for an oiled finish is understanding what are the potential sources of damage. The chart above provides a reference for what to keep away from oiled finishes, virtually any liquid or source of heat. Doilies can help to prevent scratches. The surface can be kept clean by dusting with a dry cloth or one slightly dampened with oil. Polishes should not be used other than a lemon oil polish or Old English style polish. Old English type polishes generally have dyes added so if using one of these, it is essential to choose one without a dye added or with a dye of an appropriate color for your piece. If using one of these polishes, the rule of thumb is, less is better--wipe off any excess. The best protection for oiled finishes is wax. A layer of wax will protect the oiled surface from the minor scratching and scuffing which come during the course of normal use. Wax is affected by heat as is oil, so there is no gain there, but wax will help by providing a water resistant layer over the oiled surface.
Applying a coat of a fine paste wax with an appropriate color blended in will eliminate the discoloration of any nicks or scratches and give the piece an even, soft, satiny sheen. For this we use Liberon's Black Bison paste wax, and strongly recommend that you do too. We have tried every widely regarded wax we have heard of, none are better than Black Bison. Black Bison uses highly refined liquifying solvents and so has a very low and not unpleasing odor. It buffs well and has an appropriate sheen.
Oils penetrate the wood and accentuate the natural pattern and colors of the grain.
Oils effectively seal wood surfaces and thereby protect the wood from the varying effects of the environment.
Oil finishes yield a flat to satin sheen.
In their pure or raw form oils are non toxic natural materials.
Oil finishes are easy to apply.
Oil finishes are relatively easy to repair.
Since oils fully penetrate the wood, they do not offer any protection against scuffing or scratching of the wood surface.
Oiled finishes are easily damaged by liquids and heat.
Oiled finishes can appear dusty and dry at the surface after a while, especially in dry climates, and will need to be re-oiled to maintain their appearance.
Some oils, such as raw linseed oil, dry very slowly and may remain slightly tacky for years.