From our Technical Expert Mr. Norman Kaswell
Oil Finish Urethane Finish
Oil finish vs urethane finish on wood is a common subject, discussed and explored many times in the wood flooring industry. I believe I'm right when I say that oil finishes are common in Europe, and dominate the market. They are becoming more popular here every day. I'm 95% certain that all oil finishes on the market are made in Europe.
There are many effective oil finishes on the market, including Carver (Italy), Woca (Denmark), Osmo (Germany), Palman, Rubio, BonaKemi, and Ciranova. There are tung oils as well. All oil finishes are wipe on-wipe off products. Perhaps in the last 20 years we've learned how effective oil finishes can be, but only IF APPLIED AND CARED FOR PROPERLY. The oil finish process is just that, a process. The process is to apply the oil to the wood, allow the wood time to absorb what it can, and wipe or buff off all excess oil. The oil must penetrate the wood, and not accumulate or build on the surface. Oil finishes will penetrate deeper into wood than any kind of urethane. The more oil in the wood the more stable the wood can be. But, it is very very important that all excess be wiped, buffed, and buffed again to remove oil residue on the surface. A common mistake with oil finishes is leaving a residue on the surface. In our specifications we tell the applicator after oil applications are made to buff and buff using soft pads or cloths to remove all excess oil. And we advise the applicator that if he isn't sure he has buffed enough he should buff again, because he cannot over buff the surface. The initial applications of oil should leave a silky satiny and uniform low luster sheen at the surface.
Unlike urethane finishes, oil finishes are not available in satin, semi-gloss, and gloss. They are most always satin or matt. A common criticism of oil finishes here in the states is the natural low sheen level. Most standard oil finishes have low sheen level. However, there are hard-wax oil finishes that can be applied over a standard oil finish to achieve a higher sheen level. Creating a higher sheen level hard wax oils results in some slight measurable mil thickness at the surface. The slight mil thickness will require some additional attention. For your information, we know of an oil finish made here in the states that has some slight amount of urethane in it. So, there is good penetration, and some natural sheen. The manufacturer is essentially trying to capture the benefits of both types of finishes.
One of the benefits to an oil finish is that with limited effort the flooring can be maintained in "like new" condition without sanding or re-coating. The flooring can look new most every day. Woca makes a very effective oil-cleaner product that is used to clean and re-oil simultaneously. A cloth is soaked in the oil-cleaner, then wrung out tightly by hand so that the cloth is only damp. The cloth is then wrapped below a buffing machine, and the flooring is then buffed clean with the damp oil cleaner/cloth. The cleaner in the oil will pick up the dirt, providing the dirt was not ground into the end grain of the wood. Daily sweeping to remove sand is important. The cloth will become dirty, and it is then to be thrown away. The surface is then dry buffed with a new clean dry cloth. This simple procedure can be done at any time with no odor, and should restore the surface to a "like new" condition, all with NO sanding or dust. If done regularly (depending on the type of activity in the space) the surface would never require drum or disc sanding. I should add that several months after the initial oil applications are made the resins in the oil may shrink, and if so the flooring may appear dry and dull. This is because the wood will then take on more oil by penetration. I should also add that if an oil finished floor is left unattended for an extended period of time, and if the flooring becomes severely soiled such that the oil-cleaner product is not getting the flooring clean, there are wood cleaner products made by the oil finish companies, that are sprayed on to the surface, wet screen applied to lift the dirt out of the wood, and the surface wiped clean with towels. This aggressive cleaning does not employ sanding machines and dust. But, this aggressive cleaning will require the surface be re-oiled afterwards with the same oil used initially.
If the oil cleaner is used regularly then re-oiling with the (original) standard oil finish should not be needed. But, if left unattended, despite the floor remaining clean (from clean activity), the wood may need to be re-oiled to return it to a "like new" condition again. Spray buffing with the oil cleaner and soft cloths is also a popular method of daily or weekly cleaning. The Woca refresher oil product can be used as well to add some lustre. And, I should add that a urethane finish, if later preferred, can always be added over an oil finished floor. Once a urethane finish has been applied, oil finishes and their cleaning products can not be used without re-sanding to remove the urethane.
Urethane finishes are popular here in the states. Usually the best choice for those who don't plan to do much to maintain their flooring on some regular basis. If you are designing a retail store off the street, a urethane finish would be beneficial. After all applications of finish are applied, urethane would provide all the protection its capable. Immediately following 3-4 applications the flooring would be completely finished. However, soon after completion the surface will become soiled or scratched. Soon after completion of all coats of finish the surface will become dull, scratched, for which wax products are often used in an attempt to maintain a good appearance. There is also a tendency to walk on a urethane finish after the applications are made, before the urethane has reached full cure and hardness. If you are designing a store in the middle of a mall, where outside elements (such as sand and snow) will not reach the flooring we would recommend an oil finish.
Urethane finishes are available in matt, semi gloss, and gloss. Urethane finishes are available in colors. Urethane finishes are available in solvent based and water based version. Water based urethanes are most always VOC compliant. Solvent based urethanes are most always not VOC compliant. Water based urethanes tend to produce lighter results. Solvent based urethanes tend to darken the wood slightly. Most critics would say the solvent based urethanes produce more attractive results on wood because they naturally have an amber color. And so, the water based urethane industry offers water based sealers in several levels of amber, to be first applied to bare wood, and then the standard clear water based urethane used as final finish.
When a urethane finish becomes scratched/dull and lifeless it could be corrected by screening the surface with sanding screens to clean the surface, and re-coating with two new applications. Although this can be very effective, there is always a risk of some slight delamination of new coating over low spots in the floor. I'd be pleased to discuss this further if you question why.