Protecting oak windows

[TonyG]

I had European light oak windows installed 6 years ago and they were not sealed properly so water penetration caused the wood to blacken in places (among a lot of other problems). Since then it has been remedial work.

1. I tried Sikkens THB light oak but it came out as a really dark stain. What is the best way to remove the stain to get back to the light colour?

2. What is the best alternative finish to use to protect the wood? Something translucent I assume given how light it is?

Thanks

 

[custard]

Even in the best organised workshop you'll sometimes get staining in oak if the workpiece accidentally touches the iron sash cramps during a glue up and then gets wet while the glue squeeze out is being washed off. The answer is Oxalic Acid, a mild bleach that seems to work particularly well with oak. I've never used it remove a coloured finish but it's probably worth a try in an inconspicuous area.

For long term, external protection while still retaining Oak's natural pale colour one option is varnish. If you decide to go that route then there are a couple of points that are worth considering. If you go semi matte or satin (I would) then remember that all varnishes are naturally glossy and they have flattening agents added to cut back the shine. These flattening agents quickly sink to the bottom, so you need to stir really well both before application and also at ten or fifteen minute intervals during application. Otherwise you'll get uneven degrees of glossiness. The second point is that all varnishes, and polyurethane varnishes in particular, break down in sunlight. Consequently you need a varnish that's packed with UV inhibitors. Traditionally this was the main characteristic of Spar Varnishes (the claims that Spar varnishes allowed more wood movement are a bit dubious IMO), unfortunately the term "Spar Varnish" is now used willy nilly like "Floor Varnish". So if you really want to guarantee heavyweight UV inhibitors you've probably got to stick to one of the premium yacht varnishes like Epifanes. Hair raisingly expensive but at least you know it'll deliver what it says on the tin.

Good luck.

 

[Jacob]

Natural wood finishes don't work too well with windows - too much exposure to everything - worst in winter with very hot on one side and very cold on the other. They all go sh|t brown. Oak even worse due to staining and acid reactions so it goes black.
Personally I'd remove any thick finishes and oil them with raw linseed applied hot, mid/late summer. They would go black eventually (evenly stained!) If they don't look good then paint with linseed oil paint.

nb Oak's "natural pale colour" is very ephemeral - here today gone tomorrow, there is no way of keeping it unchanged. Left with no finish it will go a natural slivery grey just like most woods. If you oil this it goes dark brown, etc.

 

[katellwood]

I had a problem with an AWO front door turning black in patches after being finished with danish oil

As custard states oxalic acid works well in getting rid of iron staining (whatever happens stay clear of wire wool)

I refinished it with osmo uv Hard Wax Oil and never looked back, did it two years ago and still looks as nice.

Will be able to post pics on fri if interested

 

[deema]

I would endorse Osmo UV translucent oil for oak. I have oak Windows, doors and gates finished with it that are both north and south facing, all still looking excellent after 4 years. They were given two Coates to begin with and one coat every other year. You need to ensure that all surfaces have at least an 8 degree run off angle to or event standing water

 

[ColeyS1]

I would endorse Osmo UV translucent oil for oak. I have oak Windows, doors and gates finished with it that are both north and south facing, all still looking excellent after 4 years. They were given two Coates to begin with and one coat every other year. You need to ensure that all surfaces have at least an 8 degree run off angle to or event standing water

I thought twas 15 degrees ? I only remember this cause it was a pain not being able to use the 9 degree cill block ......I think

Sent from my SM-G900F using Tapatalk

 

[HOJ]

I have tried endless products on Oak windows and Doors I make, all claiming to protect them, all failing within a relatively short space of time, months not years, in some cases.

I have adopted Osmo Oil, Clear Extra, for a few years now, and this has been the most successful, however, there is still on going maintenance, it doesn't like flat surfaces, they do recommended a minimum slope of 15 degrees.

They also offer "Extra Oak" which gives more UV protection but it will darken the Oak.

Osmo also produce a "Wood Riviver Gel" designed to clean back greyed wood, contains Oxcalic acid, never used it but may be worth a look.

Just finished reviving a load of windows and doors I made 10 years ago, ended up having to sand them all down, back to cleanish wood to get a fresh start.

 

[Jacob]

....

Just finished reviving a load of windows and doors I made 10 years ago, ended up having to sand them all down, back to cleanish wood to get a fresh start.

You will have to do it again in a few years - basically the weathering process is inevitable, irreversible, unstoppable - unless you paint with linseed oil paint. Modern paint no good on oak, not much good on softwoods either.
I haven't tried it on ok myself but it's brilliant on old and new redwood
Various retailers.

Video here - the comments are worth reading

 

[John Brown]

Some of my windows have a fair amount of Ronseal two-part wood filler. WIll linseed oil paint adhere well to that?

 

[Jacob]

Some of my windows have a fair amount of Ronseal two-part wood filler. Will linseed oil paint adhere well to that?

Probably, it seems to stick to a lot of stuff. But if in doubt shellac (knotting) almost certainly will. It's the best primer/sealer of all - and linseed will stick to shellac.

 

[RogerS]

Some of my windows have a fair amount of Ronseal two-part wood filler. Will linseed oil paint adhere well to that?

Probably, it seems to stick to a lot of stuff. But if in doubt shellac (knotting) almost certainly will. It's the best primer/sealer of all - and linseed will stick to shellac.

+1

 

[HOJ]

A guy on the greenbuildng forum advocated linseed oil for his Oak joinery, never been brave enough to experiment on a customers job.

The windows I had to strip back (customer requested) had a coating of Dulux Naked wood on them, allegedly offering long
life protection, they don't make it any more because it was carp.

It had left a patchy film covering on the Oak which meant it wouldn't take any finishes, no choice but to strip back, mechanically.

basically the weathering process is inevitable, irreversible, unstoppable

I accept that, (some) customers like the fresh look to be maintained, I personally wouldn't do any thing, let them go.

 

[Phil Pascoe]

Nice a timber as oak is, I don't know why people think it's a good timber for windows. It's not.

 

[Jacob]

This stuff is best for retaining the pale colour of freshly planed oak.

 

[mikefab]

This stuff is best for retaining the pale colour of freshly planed oak.

Hilarious!