Some people think silvered wood is gorgeous, all worn and vintage-looking, mellow and warm. Others hate the look, since it makes decking, garden furniture, fences and sheds look old and uncared for. It’s horses for courses. So what causes it, does it damage wood and what should you do about it?
How UV exposure affects wood
Sunshine, rain, snow, mist and fog are the culprits for exterior woodwork misery, and we get plenty of them in Britain. Under this constant battering, wood acts very like human skin. When sunburn and windburn peels dead skin flakes off it gives way to new skin, and the grey patina you get on untreated or neglected wood is caused by layers of dead wood fibres.
Even sealed wood will go silvery over time and because dead wood can’t regenerate fresh fibres, you need to do the job on its behalf. But do you really have to? Can you just leave your wooden decking, fences, sheds and so on to age gracefully, or is it important to keep up a decent standard of maintenance and try to stop wood going grey?
Does silvering damage wood?
According to ‘The Effects of Daylight’ by Rebecca Ellison, an expert article in The Building Conservation Directory 2000:
“Wood will also gradually degrade when it is exposed to sunlight. This is because one of its main components, cellulose, undergoes auto-oxidation in the presence of UV radiation in sunlight, leading to surface bleaching.
Cellulose itself does not absorb UV, but lignin, hemi-celluloses and some dyes and pigments cause cellulose to deteriorate because they act as photo-sensitisers, absorbing UV radiation and transferring the energy. As a result some of the long molecular chains of cellulose break up, weakening the material.
As this only occurs at the surface, it generally does not affect the structural integrity of the timber.”
So it really is mostly a matter of aesthetics. Interesting… If you’d like to find out more about the science side of wood’s surface and the way it behaves, we’ve added links to two really interesting resources at the end of this post.
Can grey wood be avoided?
The short answer is, no. But you can delay the greying process by using UV-resistant wood finishing products and keeping the finish of your exterior wood in good condition. These UV-resistant products are ideal for providing extra protection for wooden cladding, garden sheds, wooden decking and garden furniture against the elements.
Does interior wood go grey?
Although greying timber is usually a problem for exterior timber that is exposed to rain and UV rays, interior wooden furniture, floors and fixings, especially in areas such as conservatories and kitchens that are exposed to strong sunlight, will eventually start to lose colour and fade too, albeit at a much slower rate than garden wood. If these areas are also subject to high moisture, such as condensation and steam, this could accelerate the greying process if the wood isn’t protected properly.
Top Tip: If you spray house plants near or on wooden furniture, make sure you dry it afterwards. Not realising in the past, I’ve ended up with one side of a wooden table slightly warped, all grey and crispy. Lesson learned.
How to prevent and treat grey wood
While it appears that leaving wood silver-grey doesn’t necessarily shorten the wood’s useful life, what if you feel it’s more shabby than chic, preferring gleaming, fresh, colourful wood in all its glory? Here’s some information and advice about how to protect wood’s glorious natural colour and sheen…
Protecting new timber
- Bear in mind most brand new timber comes pre-treated to one extent or another. It should be pre-protected with a good wood preserver or wood oil. If so, it helps to know exactly what it’s treated with so you can use a compatible product when the original finish wears off
- If not, you can use a decking oil to treat fences and sheds since it’s so water-resistant, flexible and usually comes with built-in UV protection. Most wood preservers, if over-coated with some sort of decking oil or other exterior wood oil will last for up to 5 years. Most exterior wood oils including decking oil will need a top up every 1 to 3 years, depending on how much wind rain and sun the surface of the timber gets
- Fence stains are pretty good for water protection but in our climate they’re not as good as oils. When water doesn’t sit on the surface and bead any more, its time to apply another coat
- Wood sealing products work well but like stains they’re not quite as good as wood oils. If it’s particularly wet where you live you’ll have to renew it more often than normal
Restoring old timber
- A power washer is an easy way to take off layers of dead fibres and reveal the fresh wood underneath. They’re readily available at most tool hire shops. Use a tough bristle brush first to get rid of stubborn stuff like mud and bird poop (See our post on How to Clean Decking for more help)
- Treat mildew – green and black – with a quality mould and mildew cleaner like this one from Barrettine, which’ll kill it off properly as well as getting rid of the stain
- Sanding makes the surface smooth, getting rid of splinters and rough bits and giving your finish the best chance of a long life
- A wood reviver gel is your best friend. We rate Osmo Wood Reviver Power Gel, biodegradable, odourless and specifically designed to restore the wood’s natural colour. Ronseal Decking Restorer is also excellent
- Let the wood dry for 48 hours then apply a good exterior wood oil
Top Tip: The more silver-grey your wood is, the more elbow grease and extra applications you’ll need. Like so much in life, maintenance is the key!
Now for the science bit we mentioned earlier…
Research by US wood finish experts Merillat
How can you tell, up front, the effect the sun will have on the colour of different woods, and what a UV inhibiting wood finish will do to mitigate it? It’s an interesting question, and one that the US company Merillat has looked into in some detail. It’s about cabinetry but the same principles apply. Here’s what they have to say on the subject…
“Natural sunlight contains Ultra Violet (UV) light rays that may affect the appearance of your cabinets. Merillat has tested our wood types and finishes so that you may be able to determine the approximate effect that UV rays may have on the cabinetry in your home.
The tests we use follow the American Society of Testing Materials (ASTM) standards for quartz ultra violet light (QUV). The actual results in your home will vary depending on these three factors:
1. Exposure to light (for example, direct from the South, East or West, or indirect from the North)
2. The portion of the cabinet that receives the light (top, base, etc.)
3. The wood itself. The finish does not change colour, the wood itself will.
UV inhibitors have been applied to all Merillat cabinetry. With varying exposure to UV rays, and over time, colour variations will occur.”
They’ve provided some excellent images of the effects of UV rays and various finishes on a range of woods, which you can see here.
Go geeky – The heavy, heavy science bit
The US Forest Service has also carried out some fascinating if dense research into the surface characteristics of wood. If you’d like to delve deep into the subject, here is the the paper on it.
We’re always happy to help you choose the best product for the job. Just give us a call and one of our friendly experts will be on hand to give advice and answer any questions you may have.