External iroko - Osmo UV Oil or Sikkens Cetol Filter 7 Plus

[RogerM]

Nope - I haven't a clue either, and I've had enough conflicting advice to convince me we need a test, so I've set one up.

I've used an offcut of pale iroko, and from the left I have 3 coats of Osmo UV Oil, then one coat of Sikkens Cetol HLS Plus light oak stain covered by 3 coats of UV oil, and finally on the right one coat of Sikkens Cetol HLS Plus light oak stain followed by 3 coats of Sikkens Cetol Filter 7 plus light oak. The test piece is out in the open facing due south in full sun so we'll see what happens. I'll update the thread at approx 6 month intervals, or when I remember or when asked.

 

[squowse]

Hi Roger, (I'm also a Roger)
Will watch this with interest as like you I have been making windows from iroko. In my case it is the reclaimed stuff ex school chemistry labs. The stuff I have is mostly a bit darker. I've finished it internally in tung oil, but ended up running out of time in winter to finish the outsides. It's gone quite silver already but I think it will spruce up quite easily. I don't want a "perfect" shiny finish, I am quite happy for it to look aged but not completely silver and I want to look after the wood.
I saw you mentioned Owatrol Deks Olje D1 before. Did you end up trying any? I just saw they have started selling Owatrol at my local finishes shop and ended up here after googling it.

 

[RogerM]

Hi Roger, (I'm also a Roger)
Will watch this with interest as like you I have been making windows from iroko. In my case it is the reclaimed stuff ex school chemistry labs. The stuff I have is mostly a bit darker. I've finished it internally in tung oil, but ended up running out of time in winter to finish the outsides. It's gone quite silver already but I think it will spruce up quite easily. I don't want a "perfect" shiny finish, I am quite happy for it to look aged but not completely silver and I want to look after the wood.
I saw you mentioned Owatrol Deks Olje D1 before. Did you end up trying any? I just saw they have started selling Owatrol at my local finishes shop and ended up here after googling it.

Hi Roger. I did try the Owatrol on a test piece of oak but it didn't fare well at all. It seems to work better with teak when I compare it to my neighbours boat. At the moment both the Osmo UV oil and the Sikkens Filter 7 are bearing up well. There has been some darkening of the wood but it is still looking good.

 

[RogerM]

All 3 seem to be standing up well. Predictably, the wood has darkened so that the difference between the far left and the centre panel is less marked, but all seems fine so far. The test piece has been in full sun and open to the weather.

 

[RogerM]

Latest update is that they are all standing up well. However, as you can see, there is very little difference between the UV oil over the stain compared with the UV oil on its own. There is a narrow line of grey along the top edge which may be due to UV getting to the wood from both sides near the edge. The Sikkens is still looking solid and if this were joinery I wouldn't feel the need to repaint yet. The position remains facing due south in full sun

 

[sereneblue]

There is a narrow line of grey along the top edge which may be due to UV getting to the wood from both sides near the edge"MBB

I think your experiment successfully demonstrates issues with edge-film thicknesses. If the edges are sharp, the coating tends to pull back from them leaving the vulnerable to what its being tested against.

Speaks volumes for leaving a radius or knocking off the edges with a piece of sand paper before coating.

 

[RogerM]

There is a narrow line of grey along the top edge which may be due to UV getting to the wood from both sides near the edge"MBB

I think your experiment successfully demonstrates issues with edge-film thicknesses. If the edges are sharp, the coating tends to pull back from them leaving the vulnerable to what its being tested against.

Speaks volumes for leaving a radius or knocking off the edges with a piece of sand paper before coating.

Getting a bit scruffier! Now nearly 2 years old - including 2 summers.

The section of the left which is just 3 coats of UV oil is showing severe breakdown along the top of the specimen, and it's starting to show signs of grey along the front as well.

The centre section, which is one coat of Sikkens Cetol HLS Plus light oak stain covered by 3 coats of UV oil is slightly better, which seems to indicate that a bit of pigment does help, which is hardly surprising given that sunglasses help as well.

Finally the one on the right has one coat of Sikkens Cetol HLS Plus light oak stain followed by 3 coats of Sikkens Cetol Filter 7 Plus (light oak), and this is still holding up well. There is slight greying along the front edge, but the front face and top is generally looking good. I reckon that if I had chamfered the edge, or rounded it slightly that would have held up as well.

Ignore the white spots - back in the summer some idiot sprayed his kitchen doors nearby and the overspray drifted over the test piece.

Incidently, the back of the speciment which was treated in exactly the same way and is in the shade, is pristine, and it is slightly disappointing that a product that is marketed specifically as UV Protection has come out the worst. Whilst Osmo would probably claim with some justification that this is not a scientifically controlled test, and one specimen is not enough, this IS a real world test based on how people actually use the product in real life.

 

[marcros]

interesting comparison. It is a real shame that the sikkens isnt available in a sample pot- I have a small item to do that doesnt justify a litre of each coat. What would need to be done to the Osmo UV oil for maintenance, based on the above- 3 coats every 18 months or does the old stuff need stripping/prep?

 

[JJ1]

Any update on how the finishes are holding up now?

 

[RogerM]

Any update on how the finishes are holding up now?

Currently cycling from Bruges to Amsterdam - about 180 miles. Will post new photo upon my return at the weekend!

 

[JJ1]

Thanks Roger. I'm away for a short while myself so will catch up with the thread on my return. Enjoy your cycle ride 8)

 

[RogerM]

A quick update.

This piece has been in full sun and salty wind ( we live on the coast) for 2 1/2 years now. This is the end of the 3rd summer. The left side (3 coats of Osmo UV Oil) is faring worst, particularly the top edge where not only has the wood discoloured, but the finish is peeling. The centre panel (one coat of Sikkens Cetol HLS Plus light oak stain covered by 3 coats of UV oil) seems to be holding up a little better. By far the best though is the right panel (one coat of Sikkens Cetol HLS Plus light oak stain followed by 3 coats of Sikkens Cetol Filter 7 plus light oak). Whilst this is beginning to show signs that it is weathering, I think it will probably last another summer before it would need repainting if it were a piece of joinery. However, I'll just leave it to continue weathering to see how it lasts.

Ignore the white spots on the front of the piece. Some dipstick sprayed his kitchen doors on the driveway and the overspray drifted onto it!

 

[JJ1]

Thanks for the update Roger, much appreciated.

 

[sereneblue]

Thank you. This is getting dire, I have LOADS of Osmo oil and Osmo treated products at home. Thankfully they are mostly interior. Talk about getting sold on advertisements!

 

[RogerM]

Thank you. This is getting dire, I have LOADS of Osmo oil and Osmo treated products at home. Thankfully they are mostly interior. Talk about getting sold on advertisements!

The performance of the UV oil has been disappointing. On the other hand I've found Osmo PolyX Oil for interior use to be absolutely bomb proof. I test treated a piece of oak veneered mdf with it, then spilt some red wine, tomato ketchup and coffee on it, placed a hot mug of water in the middle of the mess and left it over night. The following morning it just wiped clean without leaving a mark.

 

[JJ1]

I was planning to use the UV oil for a project but have since been informed by Osmo that their Teak Oil would be a much better option for my purpose so I'm just literally off out now to pick up a can of that.

I've also been very pleased with the results from the Osmo Polyx Oil and find it an excellent product.

 

[RogerM]

Can't believe it's 17 months since I reviewed this.

This test piece has now been exposed to the weather for exactly 4 years. The left side - 3 coats of Osmo UV Oil has continued to deteriorate and there is little sign of any protection left. The centre panel (one coat of Sikkens Cetol HLS Plus light oak stain covered by 3 coats of UV oil) seems to be holding up a little better, which demonstrates that you do get some extra UV protection from pigment. The best though is the right panel (one coat of Sikkens Cetol HLS Plus light oak stain followed by 3 coats of Sikkens Cetol Filter 7 plus light oak). The vertical part is remarkably good, although the top/horizontal edge is showing signs of weather. After 4 years in a salty environment facing south in a particularly sunny spot, this is hardly surprising and if it was external joinery I would be redoing it this year. It case there is any doubt as to whether it is the sun that is doing the damage, I've also posted a pic of the back of the piece which is in permanent bright shade, and none of the finishes have been affected to any noticeable extent.

This is the same Sikkens finish on a sapele post box which gets full sun for half the day, applied about a year ago. No sign of any degradation yet.

 

[JJ1]

Thanks for the update.

 

[eniacs]

This is a very useful test. Thanks for the information.

I have a oak front door which needs redoing and looks like I'll be using cetol 7's light oak!

 

[Skeety]

Must admit that this post made me decide to use the Sikkens over Osmo Poly X.

I used the Sikkens to treat an Iroku garden table I completely took apart and rebuilt, was originally 6ft in diameter but now 5ft as that was the size we wanted and the easiest way to remove all the damage where the finger joints had expanded and broken.

Back to topic. It's been outside in a South facing garden all year round and all it needs is a quick wipe with a soapy cloth to bring it back to the condition it was in when first finished. So glad I cam across this thread back then. £50 for the Sikkens was well spent IMO as I doubt it will need touching for another 3-4 years at least.

I did a test on one of the chairs with Osmo Poly X, epic fail after a few months. Sikkens all the way for them as I rebuild them this year!

Cheers to Roger M for the original post. I'll add a pic of the table when I can.

Jon.