Exterior hardwood door is bleaching - why?

[FiscoKing]

Hello,

I had a hardwood door and frame (Iroko) made for the front of my house.

The door was treated with cuprinol wood preservative at the shop, and with thomsons waterseal after installation.

Even though the info on the waterseal tin says one application is good for up to a year, I find that the door starts soaking up rainwater every 4 months after an application of waterseal, so I give the door a coat of waterseal every 4 months.

The door has not been painted. I don't want it painted. I selected iroko because it turns golden brown in daylight.

I've noticed that over the last 6 months, the door has started to bleach a lighter colour where the rain has got to it at the bottom:

http://i67.photobucket.com/albums/h316/goodproducts101/IMG_0544.jpg
http://i67.photobucket.com/albums/h316/goodproducts101/IMG_0543.jpg
http://i67.photobucket.com/albums/h316/goodproducts101/IMG_0546.jpg

I've obviously missed something here. I thought that 3 coats of waterseal would be enough to protect the door, but it has not worked.

1. Why is the door bleaching where the rain is getting to it?
2. What can I do to stop this process.

Protecting the door from the rain is not an option, it's my front door.
I also don't want to paint it, unless there is a clear matt lacquer available.

As an aside, I made a small stand out of meranti hardwood for a large plant pot, and this sits next to the door. Went into service at the same time as the door. I gave the hardwood stand a single coat of waterseal when it went into service and then left it. The timber started out deep brown and has now gone almost white. What seems to have happened to the meranti pot stand is happening to my door at a slower rate.

Is the above bleaching normal for hardwood?

Thanks.

 

[gregers]

is your door facing sunlight light?

 

[^woody^]

Bleaching is caused by the sun, so I can't see how umpteen coats of waterproofer will prevent bleaching. Nor preservative, thats for something else too

 

[FiscoKing]

The door faces West, so it gets the sun in the evening.

Iroko gets darker with sunlight though, and it's only bleaching where the water gets to it, in the last picture, you can see where the rain splashes have hit.

If it was the sun, then the whole door would be bleaching at an even rate would it not?

I'll have a word with the shop that made it and ask their opinion. Water is involved in this somehow.

Perhaps I should have used a varnish.

 

[FiscoKing]

I've done some more research and it would appear that Thomsons Waterseal is not enough, even if you apply it 3 times a year.

The problem is that waterseal is only water repellent, not waterproof, and it also does not block UV light. The persistent rain on the door is washing the waterseal out of the wood, and the resulting wetness and UV light is turning the hardwood grey.

The solution I've been told, is to sand the wood back to its natural colour (the grey discolouration is only surface deep), and then treat with wood preservative and finally a waterproof and UV stop outer coat.

I spoke to sikkens, but they do not offer a UV resistant and waterproof coating that is clear. All their paints are tinted.

It turns out that Sadolin do make a clear paint that stops UV light, and it's sold in B&Q: Sadolin extra durable clear coat exterior. B&Q even had a sample of wood with some of this painted on. It comes in two types, matt and gloss finish. The sadolin helpline told me however that the application temperature has to be 8 deg. C for it to work, and the wood has to be dry.

So we're looking at next summer then.

If anyone has anything to add to this I'd be interested.

Thanks.

 

[JohnD]

I don't like Sadolin, it is very opaque and obscures the grain.

Have you considered Linseed Oil or similar? I used that on my external hardwood and it seems to be lasting well. It throws off the water fine.

With each coat, you are supposed to apply no more than will soak in, and wipe off any excess that lies on the surface (otherwise it forms a soft varnish). The first few coats you can thin with White Spirit so they soak in more. I applied half a dozen coats or so, in warm sunny weather, when it soaks in and dries faster. It has a slight but pleasant smell when the sun hits it.

I used Colron timber stain first to even up the colour as I was working with old wood. I used Cuprinol Clear preservative first of all.

 

[Bilioustrumpstaine]

So we're looking at next summer then.

If anyone has anything to add to this I'd be interested.

Thanks.

As long as next summer isn't like the one we just had

 

[FiscoKing]

I found a good article on why wood degrades in the open. I think rules prohibit me from adding the link here directly. If you search for 'Why wood weathers' in google, the link comes back as the 1st result (hosted by woodsealants.com). A very informative article.

If the article is to be believed, it is the UV light that's turning the timber grey.

JohnD: the article also talks about natural oils like linseed oil, but states they contain sugars that promote mold and mildew, in the right climate. The article is American, so this might not be a factor for Britain. It's worked on your door, so perhaps in Britain linseed oil is OK.

I'll try a test patch with Sadolin, and if the grain is obscured, will try the linseed oil.

Thanks.