Linseed oil?
Tung oil?

Gori is, I think, the brand Vrogum use for their factory applied finishes and as such is probably Danish. Doubt you will find it in the shops over here.

I don't keep any trade secrets, but I'm quite sure that surface coatings are not going to affect how oak moves. I expect Vrogum use Gori because they think they can sell the stuff and make loads of money. Some people make money by selling plastic windows but that doesn't mean they are any good.

I wouldn't claim to know anything about the behaviour or the sort of wood used in a lot of windows these days. :)
But to ensure that oak stays sound, you shouldn't coat it with anything that is not vapour permeable. If you try sealing the wood, sooner or later the seal will fail and water will get in and not get out again. The moisture content will rise making rot more likely. Un-coated, the wood will dry out.

It's a fair point Richy, but the sections used in window frames are more square-ish rather than flat like the planks of a boat, so there is less tendency to cupping.

Hi all,

we are currently renovating a barn in the cotswolds and plan to have solid oak windows on cotswold stone cills, however having had samples of these materials outside for a couple of weeks we soon realised the oak was bleeding black stains into the stone. Our builders have advised that this is normal and that linseed oil prevents this however I really don't like how this changes the natural colour of the wood. Any ideas of anything else we could use to prevent this?? thanks...

Any tannin that washes out of new oak onto the stone will wash away and/or fade with time. Don't worry about it, Sally. It will pass. Linseed oil won't prevent this but you may like the appearance - try it on a small section and then decide.

Yes Joe, http://www.biffvernon.freeserve.co.uk and e-mail via the blue name above. But form an orderly queue behind Jane.

Mixing oil with turpentine will tend to allow further penetration but with oak it won't get far whatever you do. It's essentially a superficial treatment.

Posted By: rogerwhit
The notion of quarter sawing for a squarish section is somewhat spurious.

Fair point. I suppose what I had in mind is that one would like the timber to have been selected with a degree of consideration for future movement, and I'm so used to thinking of quarter sawn wood when stability is called for that I didn't give it much thought. There are areas of a board sawn through that I wouldn't want, though.

what's yr location? there's no single answer.

1) Leave them un-finished - if they swell they could be trimmed to maintain the closure (groan).

2) A possible downside though, that I haven't tested, is that this could, through wetter wood, lead to the d-g unit seals failing sooner than otherwise. Which would suggest - a finish!

3) But not being in the wet west, you wouldn't need a totally waterproof finish, as long as it's breathable to let what gets in, get out. So try oil-based ones. Sorry can't say which.

I'm a joiner and I've made untreated oak doors and windows on a few occasions, and I wish people would treat them.
Firstly,none have yet gone this silvery grey that supposedly they will, they just look grungey-this is in london, mind, the rain is fairly grubby. On the sustainability issue, I don't believe that they will last as long-oak can be splitty,and when it is subject to variations in surface moisture, coupled with frost damage, surely that tendency will be exacerbated. There is more of a risk of them twisting or bowing as well- nice and warm and dry on the inside, wet and cold on the outside. No-one has got back to me and complained of that, but I've always told them that I thought it was a bad idea not to treat them, and that they might move, so maybe they wouldn't have done.

thanks all for your advice

What would you treat them with Paul?

If you want to see what old oak looks like look at an old building. A very old building. From before 'finishes' were invented.

Whoa there, bit of confusion setting in. How can something be 'good though fairly noxious'? The 'organic' you are talking about is not the compost your own no sprays gardening type. It means carbon based chemicals, some of which taste nice and others cause instant death.

Dunno what you've done with Danish oil, but your description doesn't fit my experience. Danish oil is only tung oil with some driers added and more expensive than the basic stuff. There are different qualities of linseed oil - a bit like olive oil with first cold pressings all the way through to stuff that has been through more than the proverbial mill to wring the last drop out. The best (get the Swedish stuff from Holkhams) doesn't have much protein which is what the slime moulds that make things turn black feed off. I haven't tried it but I'm told the feed quality linseed oil that the horsey fraternity drink is good, and cheaper.

Anything that involves sanding down and re-coating after a couple of years is not for those of us with a life.

As I said before, just leave the oak alone to enjoy the weather and it will be fine once you've both had the sun on you.

Sorry, Paul, I didn't notice your footnote. Doh.