Products: What to finish new "untreated" oak windows with?

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- CommentAuthorCWatters
- CommentTimeMar 3rd 2009 edited
Posted By: AlexkHi, i am a joiner and have made numorous oak products, both green and seasoned oak. With my oak windows which i have made for people and also for my own green oak barn that i am self building at the moment in Hadlow down, East sussex, i always use teak oil on my exterior joinery i find that it is much weather proof than linseed oil and danish oil. you should not be using danish oil on exterior products.

I think the make is important. I have a lot of external oak on my house treated with Danish Oil. When built it went horrible over the first winter. I suspect the brand used might not have been rated for outdoor use. That was all cleaned off and 4 coats of Rustins Danish Oil (which they rate for exterior use) were applied last summer. So far this winter it's holding up much better.

Rustins appear to suggest if you want a gloss finish go for Teak Oil and for matt use Danish - so perhaps their products are similar?
- CommentAuthorbiffvernon
- CommentTimeMar 3rd 2009
It's very difficult to find out just what goes into manufactured composites like Danish and teak oils. You get hints from the hazard data sheets but you won't find an ingredients list on the tin. I believe teak oil usually has a proportion of 'varnish', and hence gives a more glossy finish than Danish. We need an industry mole :)
- CommentAuthorAberborthin
- CommentTimeApr 21st 2009
Hi is this tread still alive, Im a newby so not sure if anyone will be looking at this after over a month?

Just in case, my question is about the use of vegitable oil to treat oak. I have been told that vegitable/cooking oil will provide a cheap means if treating oak by a builder.... Not heard anyone else supporting this idea and have so far only found one comment on an American forum that stated never to use veg oil as it never dries and will go rancid - a so called eco builder has even suggested recycling chip oil.....

welcome any thoughts.
- CommentAuthorbiffvernon
- CommentTimeApr 21st 2009
That's an interesting question.

I use olive oil or anything else that comes to hand for kitchen things like chopping boards and wooden bowls but that's a different matter.

Linseed and tung oil oil are known as 'drying oils' as the readily polymerise in the presence of oxygen from the air. That makes them set or 'dry'. I suspect that cooking oils like rape, sunflower, palm etc don't do this so quickly so might stay sticky on the timber surface for a long time.

There's a good artickle on Wikipedia: http://en.wikipedia.org/wiki/Drying_oil

I notice there that walnut and poppy are drying oils.

And quite a lot else.
- CommentAuthorowlman
- CommentTimeApr 22nd 2009
Hi biff,
I agree about them remaining sticky. What about using Terebene driers with veg oil, I've never tried it have you?
Worth a try Aberborthin?

Mike
- CommentAuthorjaey
- CommentTimeApr 29th 2009
Hi,

Is this the place to ask about treatment to finish our new green oak truss installed in our new-build with aged oak beams reused as lintels over the windows. The old oak lintels are drying to a dull brown and the truss is very pale and weeping dark tears as we were warned it would when the polythene wrappers came off.

Our joiner is not happy to leave it untreated to age and I guess it would take a long time to match the old barn purlins over the windows.But I hate the 'varnished' look and recall a Scandinavian milky wood treatment in the 70s which coated and fed the wood but only slightly darkened its colour. Any help on this and what to do with the dark tears which will not weather as Biff suggests indoors.

Thanks for any help,

jaey.
- CommentAuthorowlman
- CommentTimeApr 30th 2009
Hi jaey,
Are you trying to keep the "light" new colour? "Rustins" do a 2 pack wood bleach which presumably,once dry, could then be overcoated with something else; oil, wax, lacquer etc. I don't know how effective, or advisable, it is on green oak, your joiners may know from experience. you may have to wait until the moisture content drops. Give Rustins a call, in any case experiment first. In general though, trying to stop wood colour changing as it ages is like trying to do a King Canute. Many modern, natural or even tinted finishes are very good an don't give that caked on look that varnish does, so perhaps you could tone down the new wood colour slightly so the difference from the lintles isn't initially so great, and then let ageing do the rest. As the wood shrinks and contracts with age some lacquer type surface coatings may start to crack and blister, so perhaps an oil, or waxoil type finish may be better and more able to accomodate wood movement.

Mike
- CommentAuthorCWatters
- CommentTimeApr 30th 2009
Danish oil will give a matt, silk or gloss finish depending on how much you apply and if you appy with a cloth or brush. Try brushing on a coat and rubbing off with a cloth. Experiment on a scrap first. Osmo hardwaxoil gives a slightly "new" look. We have Danish oil on the beams and Osmo on the floor. Be prepared for the wood to split and shrink quite a lot what ever you do. Some of our split others didn't. All adds character.
- CommentAuthorbiffvernon
- CommentTimeApr 30th 2009
Don't rush. I suggest you do nothing for 12 months and then decide when you've seen what has happened.
- CommentAuthorNala
- CommentTimeMay 7th 2009
I live in a green oak framed house constructed five years ago. It is part clad in oak boarding externally. All the oak is French. It has received no protective treatment whatsoever and the cladding and external oak has silvered quite nicely. However, where tanins have run over patinated lead flashing it has left it very discoloured - and it doesn't wash off with rain.

Changing topic slightly, I have 20 quite large double glazed K glass units that in many cases are simply stuck to the frame with double sided tape or silicone and then capped with oak around the edges to keep them in place. They don't leak, but three have cracked for no apparent reason. The oak has shrunk back, but the glazier was aware this would happen and it appears to be uniform. Anyone else experienced this problem or can offer some ideas? The manufacturer of the units is suggesting thermal stress - apparently glass doesn't like sunlight!
- CommentAuthorbiffvernon
- CommentTimeMay 7th 2009 edited
It would be a shame if we discovered that putting glass in the sun was bad for it.

I suspect the stress that caused the breaks was due to movement of the green oak. We discussed this a while ago and I said that it was basically a bad idea to glaze directly onto green oak - a safer method being to glaze into separate frames made from relatively smaller section seasoned timber.

I suppose from your experience one might conclude that you get away with 17 out of 20 times.
- CommentAuthorowlman
- CommentTimeMay 8th 2009
I think biffvernon is right. Not so much the shrinkage of the wood but the twisting or warping or bowing of the frame, as it dries, putting extra pressure in one spot,or perhaps two, say top and bottom. It wouldn't have to be much movement to crack large units. You can use quarter cut green oak to mitigate the movement effects but better to do what biffvernon suggested and glaze into separate frames to be sure.

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