If you are considering refinishing or refreshing an existing finish with Waterlox products, it helps to know what type of finish is currently on the surface. If you were the one who finished it previously or you have good notes from the previous owner, then you can move right on to our Quick Guide: Waterlox and Other Finishes. If the previous finish was a Waterlox finish, then you should visit our Refinishing a Waterlox Finished Surface guide. If you are unsure about what the existing finish is, here are some helpful tips on how to identify what is currently there.
There are a wide array of finish options available and while it is probably impossible to identify the exact version of product that was used previously, there are a few methods to help at least identify the general category of finish that was used.
Wax
Wax is usually the biggest obstacle when it comes to recoating or refinishing. Wax can sometimes be a main component in some finishes, like hardwax oils and butcher block conditioners, or it can be added as an additional layer or maintenance coat on top of another finish. Wax forms a very loosely bonded layer on the surface that creates a difficult surface for other coatings to stick to and therefore, it should always be removed prior to refinishing.
Testing for Wax
You can usually identify wax by feeling the surface. For lack of a better term, the surface will feel waxy. Using the side of a coin, you can lightly scrape an inconspicuous area and you should see a waxy buildup on the side of the coin. Add a few drops of mineral spirits to the surface and cover with a shot glass. If there is wax present, it will turn cloudy and should be soft enough to wipe off. A more aggressive test would be to use a few drops of ammonia under a shot glass. This will turn the wax yellow and cause it to lift; HOWEVER, ammonia will also damage many other finishes. This should only be done in an inconspicuous area or if you intend to remove all layers of finish.
Removing Wax
Removing wax is a rather difficult process as you run the risk of merely smearing it around. The most common method is to use mineral spirits and a lot of clean rags. Allow the mineral spirits to sit for a few minutes and wipe off the softened wax with a clean rag or towel. The rags will soak up the mineral spirits and wax, so you’ll need to turn and replace the rags frequently to prevent wiping the wax back on.1 Ammonia and water or other commercial wax removers may be easier to use, but they may damage the piece or the other finishes underneath, so always test in an inconspicuous area. Sanding will usually be difficult and will simply spread the wax or drive it further into the surface.
Wax can be difficult to remove completely, proper adhesion testing should be done prior to refinishing your piece.
Appearance
You can usually tell a lot about a finish based on the way that the wood looks. In general, there are two classes of coatings: Film-formers and penetrating finishes (see Types of Finishes for more information). Film-forming finishes will have more of a “finished look” and appear smoother. Penetrating finishes will saturate into the wood and usually yield a very low gloss luster and look more “unfinished”. You can usually put film-forming finishes over penetrating finishes if they are thoroughly dry and cured.
Common Film-Forming Finishes
- (Poly)Urethane (water or oil based)
- Alkyd Varnish, Conversion Varnish, Varnish, Spar Varnish
- Shellac
- Lacquer
- Aluminum Oxide (factory prefinished flooring)
Common Penetrating Finishes
- Danish Oil
- Tung Oil (Polymerized, raw, pure)
- Linseed Oil (Boiled, bodied, pure)
- Walnut Oil, Teak Oil, Butcher Block Oil, etc. (trade names for blends of drying oils)
- Hardwax Oil or Butcher Block Conditioner (blend of oil and wax)
- Mineral Oil
Physical Testing
Aluminum Oxide (Factory Prefinished)
Aluminum oxide is a popular finish used on prefinished wood flooring because it is extremely hard. It is a difficult application process, so it will only be available on prefinished flooring. It is also relatively new (last 30 years or so), so if the floor is older, it is most likely not aluminum oxide. That being said, it tends to last a very long time, so if the floor is 20 years old and the finish looks relatively good, it probably is aluminum oxide. Refinishing aluminum oxide floors can be very difficult, so do your research if you intend to do so.
Other Film-Forming Finishes
One way to test for a film-forming finish is to see if there is a film formed at all. Using a very sharp blade, like a utility knife, scrape the surface in an inconspicuous area. You should see white, off-white or possibly even pale yellow, plastic-like shavings without damaging the actual wood. White will typically mean water based urethane, shellac or lacquer. Further testing with solvent will help to identify those more specifically. Off-white could be an oil modified urethane, amber shellac or lacquer. Pale yellow would probably indicate a spar varnish, alkyd varnish or other oil varnishes. It would be hard to further differentiate between these varnishes. If you scrape and are immediately into the wood surface, then you most likely have a penetrating finish as there is no film on the actual surface.
Penetrating Finishes
Penetrating finishes will soak into the wood fibers. They tend to wear away or dry out over time, so a general sign of a penetrating finish is the wood will look starved or dried out in areas. If there doesn’t appear to be a finish on the surface, either your wood is unfinished or a penetrating finish was used. In some cases (like mineral oil) these oils can evaporate rather quickly and leave the wood basically starved or dry. Products like these will usually require very regular reapplication.
Additional Testing: Chemicals and Solvents
Many finishes will look and feel similar. By focusing on the different chemistries, you may be able to further identify your exiting finish.
These tests will require the use of some solvents which can be dangerous if used improperly. Proper safety protocols should be followed. Most importantly will be good ventilation (or appropriate respirator), chemical resistant gloves and safety glasses. Most, if not all, of these solvents can usually be found in the paint department at a hardware store. The testing procedure will be to place a few drops of the solvent on the surface and to cover it with a cup to prevent evaporation. Shot glasses work well for this. Alternatively, you can use a cotton ball or cotton swab to rub the finish with the solvent. All of these tests should be done in an inconspicuous area or scrap piece.
Step 1: Mineral Oil or Linseed Oil
Apply or rub a few drops of oil onto the surface. If it soaks in then you have a penetrating finish. There is no easy way to identify which specific oil was used, but they generally all play well together and are rather chemically inert so mixing oils should not be a problem. For example, if your piece was originally finished with Boiled Linseed Oil (BLO), there should be no issue refreshing the piece with some Pure Tung Oil.
Step 2: Lacquer Thinner or Acetone
Lacquer thinner will dissolve lacquer. A few drops of lacquer thinner on lacquer and it should be able to wipe off the coating almost immediately. After a few minutes, shellacs and traditional varnishes will become tacky. These will typically bead up on urethane finishes, however, lacquer thinner may make some water based urethanes tacky. Further testing can differentiate the two.
Step 3: Denatured Alcohol
Shellac will dissolve in alcohol. A few drops of denatured alcohol will essentially redissolve the shellac and it will wipe off with the cotton swab. Some varnishes may soften slightly given enough time, but shellac will soften almost immediately.
Step 4: Xylene/Toluene
Xylene and Toluene are strong, aggressive solvents. A few drops will make a water based finish gummy, but should not affect oil-based urethanes or varnishes.
Is the Previous Finish a Waterlox Product?
Currently, there is no way to test if a specific product is Waterlox or not. We manufacture penetrating finishes (Pure Tung Oil, TrueTone and Universal Tung Oil Sealer) and film-forming finishes including varnishes (Marine, H2OLOX and Original) and oil modified urethanes. The previous testing should be able to help you identify which of our products was likely used, but will not definitively prove if it was indeed a Waterlox product. See What are Waterlox Finishes for more information.
Finish Identified. What’s Next?
Once you have identified your existing surface, you are better prepared with how to continue your project. You may be able to refresh the coating that currently exists, top coat the existing finish with another type of finish or you may want to completely remove the current finish and replace it with a different finish. Each type of finish has its own tips and techniques for removal or recoating and compatibility.
A few general guidelines:
- Aluminum Oxide is generally very difficult to remove and repair. Consult a manufacturer or flooring professional that is experienced with these types of coatings.
- Film-forming finishes will usually need some type of sanding or abrasion in order to recoat. If you are unsure of what was used before, it would be best to consult a professional to inspect your surface. In most cases, it would be ideal to remove completely if switching products.
- If you intend to stain or change colors of a surface that is finished with a film-forming finish, the existing finish should be removed completely.
- You cannot and should not apply a penetrating finish over a film-forming finish. The penetrating finish will not be able to soak into the wood.
- Most film-forming finishes can be applied over penetrating finishes. Some may require additional primers or tie coats. Check with the manufacturer and always test first.
- If completely unsure or concerned, you can always sand/strip to bare wood and start over.
For more information about using Waterlox products specifically with other finishes please read our Quick Guide: Waterlox and Other Finishes and our Previously Finished with Non-Waterlox Products guides.
1 Be sure to properly dispose of oily rags to prevent fires. Do not crumple wet rags and dispose of them in the regular trash.
