External iroko - Osmo UV Oil or Sikkens Cetol Filter 7 Plus
- Thread starter RogerM
- Start date
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A really interesting and useful thread which I had not spotted until now.
The performance of the Skkens product doesn't surprise me at all. The painter and decorator who I have used for painting my house for many years was a dedicated Dulux system man but switched to Sikkens products about three years ago and would not now go back to Dulux because he thinks the Sikkens lasts better. He reckons to paint houses about as often but because there is less deterioration it takes less time which keeps the price down for his customers.
I don't tend to use exterior varnishes much, but protection from UV is something that has long interested me in the context of interior finishes and the possiibility of preserving the natural colour of hardwoods used in furniture making. Some years ago I carried out an experiment using various finishes on samples of sycamore, American cherry, American black walnut and padauk. The finishes were a finishing oil, a water borne acrylic lacquer (no longer available), Osmo UVwax, Morrells pre-cat lacquer, a further set of samples with the Morrells lacquer but where the bare wood was first spayed with a factor 30, non-greasy clear sunscreen and I also had a control set of samples to which no finish was applied. The samples were all left outside in full sun over a good summer - the equivalent in terms of light exposure to many years of indoor domestic use where, even in a relatively sunny spot, much of the UV would be filtered out by window glass.
The results were both clear and interesting. There was little difference between any of the finishes and none in terms of the amount of colour change. This included the Osmo which in addition to offering no noticeable protection had the disadvatage that the opacity of the product in the tin translated into a finish which reduced grain clarity and quite obviously reduced lustre - both effects which are the last things you want on a piece of wooden furniture where the beauty of the wood is an important part of what the piece is all about. The only exception to this uniformity in results was the sample of sycamore which had been sprayed with sun screen, this had barely darkened at all. My conclusion was that sycamore must be susceptible to a particular part of the light spectrum which the sun screen was efective at screening out. I have been meaning to experiment some more with other pale species such as ash, maple and holly but have never got round to it.
Since carrying out this experiment I have discussed the issue of UV screening with a friend who is a professor of chemistry and has spent some time looking into this in the context of conservation. From this, some points have become clear. In exterior finishes, UV protection is primarily about protecting the integrity of the finish itself rather than maintaining the natural colour of the underlying wood. It is therefore no surprise that in Roger's experiment all the samples have ended up much the same darkened colour. That the Sikkens finish has superior UV protection is apparent from the fact that the finish itself has broken down very little, so preventing the weathering and oxidation of the underlying wood apparent from the greying of the other samples. My professor friend also said that the difficulty with preventing normal colour change (as opposed to greying from weathering) is that the necessary level of screening would entail such a high level of screening agent that the finish would no longer be clear, so the holy grail of maintaining original wood colours in clear finished furniture is a distant and probably forlorn one. He wasn't aware of my sycamore exception and thought it would be worth experimenting with other pale species. Given that maple is so closely related to sycamore it might be the best bet for good results. If or when I get around to some more experimentation I will post the results on here.
Jim
The performance of the Skkens product doesn't surprise me at all. The painter and decorator who I have used for painting my house for many years was a dedicated Dulux system man but switched to Sikkens products about three years ago and would not now go back to Dulux because he thinks the Sikkens lasts better. He reckons to paint houses about as often but because there is less deterioration it takes less time which keeps the price down for his customers.
I don't tend to use exterior varnishes much, but protection from UV is something that has long interested me in the context of interior finishes and the possiibility of preserving the natural colour of hardwoods used in furniture making. Some years ago I carried out an experiment using various finishes on samples of sycamore, American cherry, American black walnut and padauk. The finishes were a finishing oil, a water borne acrylic lacquer (no longer available), Osmo UVwax, Morrells pre-cat lacquer, a further set of samples with the Morrells lacquer but where the bare wood was first spayed with a factor 30, non-greasy clear sunscreen and I also had a control set of samples to which no finish was applied. The samples were all left outside in full sun over a good summer - the equivalent in terms of light exposure to many years of indoor domestic use where, even in a relatively sunny spot, much of the UV would be filtered out by window glass.
The results were both clear and interesting. There was little difference between any of the finishes and none in terms of the amount of colour change. This included the Osmo which in addition to offering no noticeable protection had the disadvatage that the opacity of the product in the tin translated into a finish which reduced grain clarity and quite obviously reduced lustre - both effects which are the last things you want on a piece of wooden furniture where the beauty of the wood is an important part of what the piece is all about. The only exception to this uniformity in results was the sample of sycamore which had been sprayed with sun screen, this had barely darkened at all. My conclusion was that sycamore must be susceptible to a particular part of the light spectrum which the sun screen was efective at screening out. I have been meaning to experiment some more with other pale species such as ash, maple and holly but have never got round to it.
Since carrying out this experiment I have discussed the issue of UV screening with a friend who is a professor of chemistry and has spent some time looking into this in the context of conservation. From this, some points have become clear. In exterior finishes, UV protection is primarily about protecting the integrity of the finish itself rather than maintaining the natural colour of the underlying wood. It is therefore no surprise that in Roger's experiment all the samples have ended up much the same darkened colour. That the Sikkens finish has superior UV protection is apparent from the fact that the finish itself has broken down very little, so preventing the weathering and oxidation of the underlying wood apparent from the greying of the other samples. My professor friend also said that the difficulty with preventing normal colour change (as opposed to greying from weathering) is that the necessary level of screening would entail such a high level of screening agent that the finish would no longer be clear, so the holy grail of maintaining original wood colours in clear finished furniture is a distant and probably forlorn one. He wasn't aware of my sycamore exception and thought it would be worth experimenting with other pale species. Given that maple is so closely related to sycamore it might be the best bet for good results. If or when I get around to some more experimentation I will post the results on here.
Jim
Nice test and thanks for sharing.
Not surprised as saw a similar test in a yachting mag some years back with lots of fancy varnish's and stains tested and Sikens beat them all hands down for longevity. Think they were testing the Sikens HLS but I admit to getting confused with all there different offerings which seem so similar. Have used there finishes on various jobs over the years and never regretted it.
Not surprised as saw a similar test in a yachting mag some years back with lots of fancy varnish's and stains tested and Sikens beat them all hands down for longevity. Think they were testing the Sikens HLS but I admit to getting confused with all there different offerings which seem so similar. Have used there finishes on various jobs over the years and never regretted it.
EdK
Established Member
Thanks Roger - I followed the advice in this post and finished a back garden gate (oak) with Sikkens 1 & 3.
Salty environment/sunny.
Coming up for three years and the front of the gate facing the sun is starting to break down - mostly on the top rail.
The reverse of the gate (shady side) is pretty much looking new.
# How do you re-finish?
I was going to rub down the front of the gate and then reapply 1 & 3 coats but then thought that I might be able to get away with just giving it a quick sand in the worst areas and just apply, say, 2 coats ?
Do I need to go back to bare wood and start again?
Thanks,
Ed
(original gate - garden-gate-oak-work-in-progress-t80647.html )
Also...
How did you get your post box finish so even?
I had issues with my oak gate and it felt like I was applying brown streaky paint.
Is it a case of much thinner coats? Foam brush?
Salty environment/sunny.
Coming up for three years and the front of the gate facing the sun is starting to break down - mostly on the top rail.
The reverse of the gate (shady side) is pretty much looking new.
# How do you re-finish?
I was going to rub down the front of the gate and then reapply 1 & 3 coats but then thought that I might be able to get away with just giving it a quick sand in the worst areas and just apply, say, 2 coats ?
Do I need to go back to bare wood and start again?
Thanks,
Ed
(original gate - garden-gate-oak-work-in-progress-t80647.html )
Also...
How did you get your post box finish so even?
I had issues with my oak gate and it felt like I was applying brown streaky paint.
Is it a case of much thinner coats? Foam brush?
Thanks Ed. When I'm recoating my bifold doors, I just wash them down, and then when dry wipe it with some 120 grit aluminium oxide paper to key the surface and give it two thin coats of the top coat. It is important to have a rounded edge to top surfaces as the finish will be excessively thin at sharp edges. I think 3mm pencil round is what the manufacturers recommend.EdK":2c9or8oj said:
EdK":2c9or8oj said:
I think it really is a case of mixing well and brushing it out thinly. Recently I have started using a Sikkens Walnut for sunny positions as it has a darker pigment which should be more UV resistant whilst remaining impressively translucent. I may set up a test comparing the Oak with the Walnut and also with Sadolin Ultra which also seems impressive.
Anyone who has found this thread useful may be interested in the new one I've just posted that compares Sadolin Ultra vs Sadolin Classic vs Sikkens Cetol Filter 7 Plus.
On top of the hill
New member
Ok i feel anxious and need some very basic help. Im new to all this.
I bought some fantastic 6 foot iroko gates.
But they have been installed in the winter...months after I ordered them.
I have taken them off...after 2 months hung outside...allowed them to dry in situ by covering them with a tarp for two weeks unhung them and allowed to dry in garage for a week
I saw the sikken experiment so have plumped for
Sikkens Cetol HLS Plus light oak stain followed by 3 coats of Sikkens Cetol Filter 7 plus light oa
I have applied the one coat stain.
Q1...Might be a stupid question...how do i know its dry?
Q2 Should i just do 1 coat or two. And how do I decide?
Q3 i am now panicking... were the gates ‘dry’ before i added the stain? How can i tell this? Im concerned because its been so cold....was i too anxious to get them done before the winter weather.
Q4 What should i do now? Go ahead with starting the cetol filetr?
Q5... is it ok to do one side and then the other in the filter?
Q6.. they are in my garage but its only 5 degrees...how long should i wIt between coats ? How can i tell its dry.
Q 7 do i sand between any of the coats and if yes what do i need to do?
I am disappointed they were not hung in sept as promised...which would have enabled me to have done all this hing outside in warm weather.
Can you knowledgeable folk help me reduce my anxiety? I love my gates and just want them to be perfect...and hence all my efforts in trying to do the right thing!
I bought some fantastic 6 foot iroko gates.
But they have been installed in the winter...months after I ordered them.
I have taken them off...after 2 months hung outside...allowed them to dry in situ by covering them with a tarp for two weeks unhung them and allowed to dry in garage for a week
I saw the sikken experiment so have plumped for
Sikkens Cetol HLS Plus light oak stain followed by 3 coats of Sikkens Cetol Filter 7 plus light oa
I have applied the one coat stain.
Q1...Might be a stupid question...how do i know its dry?
Q2 Should i just do 1 coat or two. And how do I decide?
Q3 i am now panicking... were the gates ‘dry’ before i added the stain? How can i tell this? Im concerned because its been so cold....was i too anxious to get them done before the winter weather.
Q4 What should i do now? Go ahead with starting the cetol filetr?
Q5... is it ok to do one side and then the other in the filter?
Q6.. they are in my garage but its only 5 degrees...how long should i wIt between coats ? How can i tell its dry.
Q 7 do i sand between any of the coats and if yes what do i need to do?
I am disappointed they were not hung in sept as promised...which would have enabled me to have done all this hing outside in warm weather.
Can you knowledgeable folk help me reduce my anxiety? I love my gates and just want them to be perfect...and hence all my efforts in trying to do the right thing!
Mike Watkins
Woody Woodgate
Excellent stuff and many thanks for doing this experiment, I was about to buy Osmo for my newly made oak window frame but I will definitely go with Sikkens now. Cheers, Mike.
Farm Labourer
Established Member
This has been really useful, thank you!
It's 2 1/2 years since this was last reviewed, and over 8 years since it was started, and any finish left in full sun for that time will be showing severe deterioration by now. Only the Sikkens shows any signs of giving continued protection. The Osmo UV Oil has all but disappeared.
The back of the test piece is in permanent shade and both the UV Oil and the Sikkens continue to give protection, although I question whether a product called UV Oil is correctly named if it only provides protection when shielded from UV.
This is of course only relevant to this particular product, and I remain a fan of Osmo Polyx oil, Osmo Raw and Osmo TopOil for protecting interior surfaces. I'm tempted to retire this particular test now as I think it has run its' course, but the more comprehensive test is still ongoing here.
The back of the test piece is in permanent shade and both the UV Oil and the Sikkens continue to give protection, although I question whether a product called UV Oil is correctly named if it only provides protection when shielded from UV.
This is of course only relevant to this particular product, and I remain a fan of Osmo Polyx oil, Osmo Raw and Osmo TopOil for protecting interior surfaces. I'm tempted to retire this particular test now as I think it has run its' course, but the more comprehensive test is still ongoing here.
Attachments
+1 for RogerM's original posts, and likewise sereneblue, I have Osmo UV oil, but am now going to order sikkens based on those test results!
I’ve always used just clear external uv Osmo on Iroko doors and windows. Never had any complaints/issues with the finish.
Did some recently that the customer wanted left in the white, so would go grey over time .
My opinion on it was, that we should really finish with something...for one the outside would weather a thousand times faster, if at all on the inside!
And a few years down the line when they start having expanding/warping/rotting issues and complain, we had done everything to mitigate such issues!
Not that I was listened too, customer always being right and all that!
Did some recently that the customer wanted left in the white, so would go grey over time .
My opinion on it was, that we should really finish with something...for one the outside would weather a thousand times faster, if at all on the inside!
And a few years down the line when they start having expanding/warping/rotting issues and complain, we had done everything to mitigate such issues!
Not that I was listened too, customer always being right and all that!
Paul-Saltcote
New member
Roger, I wanted to say thank you for the persistency you have shown here. After a fire at my place the balustrade was replaced at a cost of £201k of which over £10k was on the top oak handrail.
Osmo was specified and it's not performed over the last three years so I have been looking at the way forward and your post was an absolute pleasure to find. Sadly the person who did the work described himself as an artist and fitted kiln dried oak in a coastal facing elevated position. The image I attach was taken one year after the work was completed at Saltcote Place, it's now in need of a very serious cuddle and your article was just what the Dr ordered.
Many thanks
Paul
