FINISH SPOTLIGHT: Osmo Polyx Oil & Clear Extra Thin
Since we’ve been carrying Osmo’s Polyx Oil in our store, we’ve gotten some great feedback from our customers - it’s easy to apply, it has low VOC content (so it doesn’t stink up your shop and kill your brain cells), and it gives a real natural look to wood when it’s fully cured- all with the added protection of a wax finish. However, I wanted to know for myself- how did it look on our walnut? Which method resulted in the best look and feel, and how well would it hold up to water rings? How easy was it to fix? I had questions, and I needed answers.
Fine Woodworking published an article in their July/August 2017 issue about working with Osmo. In it, author Marcus Soto describes a method for applying Osmo that includes some extra steps, compared to the directions on the can. Also, we just started carrying Osmo’s Clear Extra Thin finish, which is comparable in application to a wipe-on varnish, in contrast to the thicker viscosity of the Polyx Oil. I wanted to find out firsthand what the different results were going to be. Time to crack open the notebook and start filling out some “lab” reports!
I wanted to be as scientific and methodical about this as possible, so I found a single small piece of walnut, and sent it to our shop guys to have them cut it into three pieces after sanding it to 220 grit. This way, all three pieces were at an equal starting point, and more importantly, all three were cut from the same board. From there, I wanted to try three different methods:
- Two coats of Osmo Polyx Oil, according to the directions on the can
- One coat of Osmo Clear Extra Thin, followed by one coat of Osmo Polyx Oil, according to the directions on the can
- Fine Woodworking’s “Osmo slurry” method with Osmo Polyx Oil (I’ll get into the details below)
I figured this was a good starting point; later on, I may try other application methods, or other Osmo products, but for now I wanted to keep it simple. Speaking of simple, following the directions Osmo provides for their finishes couldn’t be easier. From the label on the can of Polyx Oil:
1st Coat: Apply thinly, thoroughly, and evenly along wood grain. Remove excess immediately. Leave to dry for 8-10 hours. Ensure good ventilation and room temperatures above 18 degrees Celsius (or 64 degrees Fahrenheit).
2nd Coat: Apply thinly as above. Remove excess immediately. Alternatively, apply second coat by trowel and buff the surface with a white pad. Leave to dry 8-10 hours, ventilate well. When thoroughly dry, surface can be buffed or polished with hand polisher or buffing machine.
The only difference in applying the Clear Extra Thin is to let it sit for 30 minutes before wiping away any excess. Simple, right?
In contrast, Fine Woodworking’s method is a little more involved. I’ve outlined the steps here:
- Sand your piece up to 220 grit, making sure to raise the grain at 180.
- Add a thin coat of Polyx Oil with a cotton rag.
- Use some wet/dry sandpaper at 220 or 320 grit, and sand the Osmo into the wood. This should make a slurry.
- Use a balled up cotton rag to work the slurry into the surface in overlapping circles, similar to a French polish.
- Let dry overnight.
- Sand the surface with regular 150 grit sandpaper.
- If the wood grain is still open, sand back up to 220, and repeat steps 1 through 6.
- If the grain feels closed, sand back up to 220.
- Apply a thin coat of Osmo. Let it sit for 10 to 15 minutes. If the finish tacks up, add more and spread it around.
- Wipe up any excess, making sure to go with the grain.
- Let dry overnight.
- Repeat steps 9 – 11 for a second coat.
- Scuff sand with an abrasive pad or a very high grit sandpaper between coats.
After all of these methods, make sure to give your piece a good polish with a clean pad to even out the sheen.
So, we tried these three methods. Two are easy, and one is… well, it’s still pretty easy, just basically an extra step in the process. It will take longer than just slapping two coats on a piece and calling it good, though. We tested all three samples on feel, appearance, and resistance to water. So how did they all turn out? Here are our results.
Piece #1
The first piece got two coats of regular Osmo Polyx Oil, just like the directions on the can said to do.
Ease of application: dead simple. Really, it couldn’t be easier. Drizzle some on the top, smear it around with a clean rag or squeegee, let it sit for ten minutes, and wipe off the excess. Let it cure overnight, and do it again. After the second coat, give it a good buffing to even out the sheen. That’s it.
Appearance and feel: Unfortunately, the look and feel of the piece seemed to be the lowest out of the three. You can tell the grain is still open, with a somewhat rougher feel to it. The white cloth I used to buff the finish out left tiny fibers of cotton in some of the pores of the wood. There were also some shiny spots revealed when a light was raked over the surface. From a distance, it looks great- but up close, small imperfections like these add up.
Water penetration: As far as water rings go, this piece held up the best. Fifteen minutes of a freshly washed coffee cup resulted in an almost imperceptible ring. No difference in feel, and a quick spot repair made it look like it never happened.
Piece #2
The second piece got one coat of Extra Thin Clear, followed by one coat of the regular Polyx Oil.
Ease of application: Again, really simple. Extra Thin Clear goes on just like a wipe-on polyurethane. Apply it, let it soak in for half an hour, and wipe off any excess. Let it cure overnight and apply a coat of regular Osmo over it. When that cures, buff it out. Easy.
Appearance and feel: There’s a world of difference between this one and the first sample. The look has a much flatter sheen, and it feels a lot smoother. Fewer shiny spots are in this sample, although there are still a few here and there. The pores are definitely filled in this sample, although the wood grain still stands out a bit- no film finish here. If you don’t have the time for the slurry method, then I would definitely recommend this. The drawback? You’ll be spending almost twice as much.
Water penetration: This one didn’t hold up so well. A hazy white circle appears after fifteen minutes of setting a wet coffee cup on the piece. It feels fine; no raised grain in the wood. If you ran your hand over the spot without looking, you wouldn't notice it at all. Still, this one had to be sanded off and reapplied- no simple spot repair would get rid of the ring.
Piece #3
This piece got the slurry treatment from Fine Woodworking.
Ease of application: this method takes some time. You’ll also be using more finish than the first two methods (although not all that much). Really, the most effort you’ll spend here is getting the consistency of the slurry just right, so you can work it into the wood grain. If you don’t add enough Osmo, you’ll have to spend a lot of elbow grease to work your paste into the surface. If you’re getting winded working the slurry into the surface, add a little bit more Osmo. Don’t add too much, though- you can dilute your slurry to the point where the solid particles (the sawdust) essentially float away, and you’ll have to start all over again (please don’t ask me how I know this). Remember- a little bit goes a long way.
Appearance and feel: Truthfully, it’s almost identical to sample #2. If you blindfolded me and told me to tell one from the other, I honestly couldn’t do it.
Water penetration: Again, the results were almost identical to #2- a hazy white circle showed up after fifteen minutes of supporting a wet coffee cup. This piece also had to be refinished, same as the second one. 
Repairs
Let’s face it- at some point, you’ll probably need to fix a scratch or water ring on your finished piece. Well, you’re in luck; we tested this process as well!
Piece #1: a simple spot repair (dipping a gloved finger into a can of Osmo Polyx and smearing it on, waiting ten minutes, and wiping off the excess) was all it needed. Good as new.
Piece #2: sadly, this one had to be sanded off and reapplied. Same process as before, using the Extra Thin Clear as a sealer coat, and the regular Polyx Oil over the top of that, got rid of the water ring. Not a huge ordeal, but I could see it being a pain if you're just trying to fix one spot in a much bigger area like a tabletop.
Piece #3: this piece got the same business as number two- sand off, reapply. Took a bit longer due to the slurry method, but it worked just fine in the end. Again, I could see this being a pain on a bigger piece.
Conclusion
At this point, it’s pretty apparent that using the Clear Extra Thin is more or less equivalent to Fine Woodworking’s slurry method. Pieces 2 and 3 were almost identical in every way, even including how they responded to water rings. Assuming you want your final product to have that buttery-smooth feel to it, you’ll have to make a decision- do you want to spend the extra money for another can of finish, or would you rather save a few bucks and spend the extra time and effort in making a pore-filling slurry? That’s not something I can decide for you, although I will say that using the Clear Extra Thin sped up my total finishing time considerably.
Piece #1 has a noticeable difference in feel, but some time spent with an ultra-fine grit sanding pad will knock it down a bit to help smooth it out. You’ll still have the open pores to deal with, however, so I’m not sure I’d use this method for a piece I was making for a client. Pieces #2 and #3 feel extremely smooth to the touch, although the color looks just a shade lighter than Piece #1, to me.
To sum up, if you've got a few extra bucks, buy a can of both the Polyx Oil and the Extra Thin Clear. If you don't, use the slurry method. The results are almost identical, and both are better than just the Polyx Oil by itself.