The Best Outdoor Wood Finish

Cetol Door & Window can be found under a new line name of ProLuxe by Sikkens. It retails for about $70 per gallon.

Cetol Door & Window can be found under a new line name of ProLuxe by Sikkens. It retails for about $70 per gallon.

I often get asked, “What can I put on wood that will protect it outside?” My follow-up question is, “Do you want a finish that builds up to a film or just something that soaks in, like an oil?” If the answer is a film finish, I recommend Cetol Door & Window, from the Sikkens Proluxe line of wood finishes. It holds up better than any other outdoor finish that I have used, and every painter that I know and trust uses it too. I have found Cetol to last almost twice as long as the next class of film finishes.

In my teenage years, I tried regular ol’ Minwax polyurethane on the wood bed of my restored ’63 Chevy pickup truck, and I couldn’t believe how fast it started to peel. One St. Louis summer of constant heat and sun made it look like it had a bad sunburn with lots of dead skin.

After that, I moved on to other products like spar urethanes (Minwax also makes one of those, called Helmsman’s). Yes, it lasted longer, but not LONG. It started to look bad after a little more than a year. It didn’t totally fail all at once, but enough areas were falling apart that it didn’t really matter – it just looked bad.

In defense of these two products, the bed of a pickup truck is a tough environment. It gets direct sun, extra heat with no breeze, and the surface is horizontal, so water has a much better chance of nosing its way under the finish. It really gets no more demanding than this for a wood finish.

With yearly maintenance, the spar urethane could be kept looking reasonably good, but eventually the maintenance gave way to submission and the weather won. The boards still looked alright (nothing rotted through), but there were always spots where the finish failed and the beautiful clear-coated lumber had cracked finish and gray spots of raw wood.

It wasn’t until much later that I was introduced to the Sikkens brand name from a friend in the St. Louis Woodworkers Guild. He had great things to say about their products, and then I started noticing them being used by different painters on different jobs around town – and consistently. Nobody was using anything else, at least not anyone that I trusted, so I started using them.

Originally, Cetol only came in various forms with added stain. Some of the colors were pretty light, but none were clear. I believe the color is added to help with UV protection, but it does nothing to help color matching or achieving a clear finish. Now, with the name change to Proluxe, a colorless version is available, and it is the one that I use.

The can says that Cetol should be applied with a brush and not rolled or sprayed. I haven’t rolled it, but I have brushed and sprayed it, and both worked fine. Spraying is more difficult, and probably not recommended by the company, because the Cetol has a long working time and tends to sag if applied too liberally. That same working time is great for brushing and allows large areas to be worked and reworked to blend brush strokes. If you do try to spray it, start with a light application and allow it to settle for a second so you can get a feel for how it is going to sit down. Keeping a wet edge isn’t critical because it doesn’t even start to get tacky for a long time and the following passes will easily blend together. If you do spray the Cetol be vigilant about finding areas that start to sag or run and simply blend them in with a brush.

Cetol, like many other finishes, takes three coats to build a good protective barrier. A fourth coat will add a bit of extra protection, but isn’t required. I would opt to skip the fourth coat on the initial application and put that energy to a maintenance coat later down the road.

Regular maintenance is critical to keep the finish from failing. Keep an eye out for areas that start to crack and get another coat on as soon as they appear. If you wait too long it will be necessary to completely strip the finish and start over.

Cetol should last for several years without maintenance on vertical surfaces and even more if they are protected from the sun. Horizontal surfaces in the sun will probably last a maximum of two years before they require attention. Both of these time-span numbers are not great, but they are at least twice as long as the spar urethanes. If you jump around the internet and read about other choices or recommendations from other woodworkers, you won’t find anything that lasts longer.

Unfortunately, three years is really the maximum for an outdoor clear finish with sun exposure. Of course, if you know of a finish that lasts longer please let all of us know about it. But, do watch out because the world will beat a path to your (long-lasting, clear-coated wood) door.



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About wunderwoods

Hi! My name is Scott Wunder and I am the owner of WunderWoods Custom Woodworking. We build wine cellars, built-ins and furniture from local woods, here in St. Louis, MO. Recently, I finished a three-year term as the President of the St. Louis Woodworkers Guild, which had me writing a monthly article for our newsletter. I love to write, especially about wood, and found that I still had more to say. Every day I run into something wood related that I realize some of my customers don't know and this seems like a great forum for sharing what I have learned (instead of telling the same story to each person). The main thing to remember is that I try to keep it light and as my wife always reminds people that have just met me, "He is joking."

6 responses to “The Best Outdoor Wood Finish”

  1. gmail personal says :

    Have you any experience with tigerwood used for decks? ( I guess considered a Brazilian hardwood?). I am trying to find a good stain/sun protector to keep the color of the wood versus the grayling that has occurred. Wondering if this product would work?


    Terri Halloran

    Sent from my iPad


    • wunderwoods says :

      As long as the finish is maintained it will keep the wood looking close to new. The color will darken, but it will still look like finished wood instead of gray driftwood. The problem is the maintenance part. On a deck, it most likely won’t happen at regular enough intervals, since you have so much to cover, and once it fails you will have to sand and start over to make it look good, which also probably won’t happen, so you will be left with a 1/2 gray driftwood, 1/2 new wood and a lot of peeling finish. Decks also suffer from the fact that a good percentage of the wood is in a spot that is hard reach and cover. I wouldn’t use this on a deck, and I wouldn’t recommend anything that forms a film finish on decks. I would recommend oil-based semi-transparent deck stains in your situation. They will not keep the original color of the wood, but they don’t peel and you will never have to sand and start over.

  2. Dan Fall says :

    I have given up on any film finishes for outdoor use. It is just too much headache to strip and reapply in a few years. I put a beautiful Epifanes Marine Wood Gloss on a bench. It was pretty amazing. My wife was in awe. I put it outside in May and in August-hailstorm. Six hours later finish was gone and a no build finish was on it. I think the type of exposure is a paramount factor. Sun, rain, hail, ocean spray, temp swings, highway dirt-all these and others are really hard on film finishes. Dust in the house is no comparison.

  3. Taylor Bishop says :

    Thanks for going over a good wood finish to do for the outdoors. I had no idea that maintenance in general is important to make sure that the fishing lasts for a long time. Perhaps it could be good to know in advance what maintenance is needed, especially if it depends on the material of the wood or the finish.

    • wunderwoods says :

      The key is to maintain an unbroken film of resin on the surface of the wood. There are so many forces working against it outside that you have no choice but to work on it regularly to guard against failures.

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